Regear 8-speed from 3.3 to 3.9?

[Artie]

So it looks like Santa may come early this year… Christmas in July is still a thing I think.

Anyway, we’re strongly considering making the jump to 3.9’s but I want to make sure I don’t have any blind spots. Here are the issues I want to solve:

1. The power hole I have when doing any mountain passes while towing. The 2nd gear- foot to the floor- 4800 rpm slog while conveyer temps hit 250+

2. The weird space I find myself in on dirt roads while towing where I can’t maintain 45mph + to keep the converter locked up so the temp gets 250+ if I stay in 4 hi. I can get around this by using 4Lo but now I’m maxed out at 30mph but the road is nice enough to go faster.

3. Those interstate drives like Oklahoma or west Texas where it’s flat and windy enough that I can’t stay in 6th gear at 75mph so it drops to 5th and I gain MPG hell for 300 miles.

4. Sometimes a little more engine braking would be nice.

Those are my main complaints given my build weight and all the towing we do (80% of our miles we have the trailer.)

These issues won’t be completely solved with the switch but I expect them to get much better based on all the reading I’ve been doing on here.

What will I be giving up? Will I still be able to run 75-80 mph on the interstate while towing if conditions call for it? I’ve looked at the spreadsheet one of yall posted with gear ratios, rpm, and MPH with 34” tires and it looks like my rpms will be about 500 higher for the same speed or roughly 10mph slower for the same rpms.

What could I be overlooking or not understanding here?

 

[linuxgod]

I can’t speak to the 8 speed, but I found the 6 speed going from 3.90 to 4.88 on 34s was a bit over geared if I couldn’t hold 5th with the torque converter locked up. When it’s in 4th I’ll run 3500+ RPMs consistently on the highway and get like 5.5mpg when towing. Sometimes I wish I had 4.30s if I’m in hilly terrain and need to hold 4th because of the MPG hit. But if I can hold 5th locked 4.88s are nice and I get an extra 0.5 to 1mpg vs stock gears and running in 4th

I don’t have any trouble maintaining 75 most of the time though I do recommend running premium fuel or at least in my case I’ll find if the temps are hot out or if there’s a strong crosswind the ECU retards timing and the engine loses power.

My trailer is 6000# btw

 

[K9LTW]

1. The power hole I have when doing any mountain passes while towing. The 2nd gear- foot to the floor- 4800 rpm slog while conveyer temps hit 250+

3. Those interstate drives like Oklahoma or west Texas where it’s flat and windy enough that I can’t stay in 6th gear at 75mph so it drops to 5th and I gain MPG hell for 300 miles.

We just did our annual trip out west from here in VA and I laughed reading your post as I can, seriously, relate. We just got our '16 in January, so this was the first trip with it while towing our ~4k lb when loaded Arkto G12 trailer. We took 90 out as we spent a couple nights outside of Badlands NP and GREAT googaly moogaly slogging across SD suuuuuuuuuuuuuuuuuuuuucked. It was exceptionally windy that day (35-40+ sustained winds right in our face) we pulled into camp and I gave up trying to keep it in S6 as I couldn't even maintain 70mph without it constantly hunting between 5th and 6th even with the OTT spicy tune with ECT. I also noticed it seemed a bit bogged and very reticent to downshift as the day wore on which now has me a bit concerned my E&E skid plates may be causing some heat soak due to a lack of any venting/drainage. No I didn't have anything set up to monitor temps beyond the stock gauges. Yes it's on the list.

And the mountains. HA! I've never had range anxiety in an ICE vehicle...until now. Quite literally could watch the fuel gauge move when I was flogging it to get up to South Pass City from Lander, WY. In 3rd gear, screaming, just to maintain about 45 mph. The 12.5-gal LRA just shot to the number 2 spot in future mods (after sliders) as there are some long stretches out there between fuel stops and some of them are questionable...and that's when you're just sticking to tarmac.

I'm only running 33s and slick. My solution isn't really leaning towards regearing, though. I'm looking at supercharging (gonna suck needing premium, though). The other solution is that I hope to only do that miserable drive one more time...and that's when we're moving as we're building outside of Lander. Given that we'll be at pretty decent altitude for the vast majority of any future adventures, forced induction just makes sense to me.

The whole point to taking the Cruiser on this trip was to go explore away from camp and the ease of bopping around town during the time we stayed at a friend's house. And we, certainly, got into some trails our RAM wouldn't fit. But, MAN...it's kinda sad when a Power Wagon on 37s (granted it has 4.10s from the factory) with a pop-up camper on the back gets better MPGs towing that same trailer while cruising 75 all day long with nary a hiccup.

 

[Artie]

I can’t speak to the 8 speed, but I found the 6 speed going from 3.90 to 4.88 on 34s was a bit over geared if I couldn’t hold 5th with the torque converter locked up. When it’s in 4th I’ll run 3500+ RPMs consistently on the highway and get like 5.5mpg when towing. Sometimes I wish I had 4.30s if I’m in hilly terrain and need to hold 4th because of the MPG hit. But if I can hold 5th locked 4.88s are nice and I get an extra 0.5 to 1mpg vs stock gears and running in 4th

I don’t have any trouble maintaining 75 most of the time though I do recommend running premium fuel or at least in my case I’ll find if the temps are hot out or if there’s a strong crosswind the ECU retards timing and the engine loses power.

My trailer is 6000# btw

If I understand all the 6 speed-8speed comparisons, your move to 4.88 would compare similarly to the 8 speed going to 4.3.

I’m trying to make an improvement without going overboard. 4.3 on the 8 speed sounds like it’s pushing the over geared boundary for many. Again, a lot of this dependent on the driver. However, I do feel like I need some change to offset 34” tires, and a 8k lb cruiser with high profile front bumper.

 

[Artie]

We just did our annual trip out west from here in VA and I laughed reading your post as I can, seriously, relate. We just got our '16 in January, so this was the first trip with it while towing our ~4k lb when loaded Arkto G12 trailer. We took 90 out as we spent a couple nights outside of Badlands NP and GREAT googaly moogaly slogging across SD suuuuuuuuuuuuuuuuuuuuucked. It was exceptionally windy that day (35-40+ sustained winds right in our face) we pulled into camp and I gave up trying to keep it in S6 as I couldn't even maintain 70mph without it constantly hunting between 5th and 6th even with the OTT spicy tune with ECT. I also noticed it seemed a bit bogged and very reticent to downshift as the day wore on which now has me a bit concerned my E&E skid plates may be causing some heat soak due to a lack of any venting/drainage. No I didn't have anything set up to monitor temps beyond the stock gauges. Yes it's on the list.

And the mountains. HA! I've never had range anxiety in an ICE vehicle...until now. Quite literally could watch the fuel gauge move when I was flogging it to get up to South Pass City from Lander, WY. In 3rd gear, screaming, just to maintain about 45 mph. The 12.5-gal LRA just shot to the number 2 spot in future mods (after sliders) as there are some long stretches out there between fuel stops and some of them are questionable...and that's when you're just sticking to tarmac.

I'm only running 33s and slick. My solution isn't really leaning towards regearing, though. I'm looking at supercharging (gonna suck needing premium, though). The other solution is that I hope to only do that miserable drive one more time...and that's when we're moving as we're building outside of Lander. Given that we'll be at pretty decent altitude for the vast majority of any future adventures, forced induction just makes sense to me.

The whole point to taking the Cruiser on this trip was to go explore away from camp and the ease of bopping around town during the time we stayed at a friend's house. And we, certainly, got into some trails our RAM wouldn't fit. But, MAN...it's kinda sad when a Power Wagon on 37s (granted it has 4.10s from the factory) with a pop-up camper on the back gets better MPGs towing that same trailer while cruising 75 all day long with nary a hiccup.

We did a couple weeks in Wyoming a couple years back, our 40 LRA tank was clutch.

Supercharger is tempting but I’m just not ready to modify the engine, we only have 40k miles and I’ve not seen a definitive answer on a ECU tune. If we go that route it’s gotta be done flawlessly. Gears, on the other hand, may also be pricey but the downside risks are much less.

We don’t care about MPG, I’m more concerned with converter temps and RPM’s.

 

[K9LTW]

We did a couple weeks in Wyoming a couple years back, our 40 LRA tank was clutch.

Supercharger is tempting but I’m just not ready to modify the engine, we only have 40k miles and I’ve not seen a definitive answer on a ECU tune. If we go that route it’s gotta be done flawlessly. Gears, on the other hand, may also be pricey but the downside risks are much less.

We don’t care about MPG, I’m more concerned with converter temps and RPM’s.

So Magnuson provides an intial tune, and my local OTT tuner has refined them farther on customer vehicles. I feel pretty comfortable with it, but won't be hunting for more power like the Tundra folks. No argument there with gearing! You also don't have to source premium fuel, which can be problematic at times in some remote areas out west.

We're sticking with the 12.5-gal as I'm trying to keep this a lightweight-ish build and don't want to resort to swingouts and such (keeping the spare inside is a non-starter). But, man...range envy with your extra tank and a half is a thing!

 

[linuxgod]

If I understand all the 6 speed-8speed comparisons, your move to 4.88 would compare similarly to the 8 speed going to 4.3.

I’m trying to make an improvement without going overboard. 4.3 on the 8 speed sounds like it’s pushing the over geared boundary for many. Again, a lot of this dependent on the driver. However, I do feel like I need some change to offset 34” tires, and a 8k lb cruiser with high profile front bumper.

I think it’s more like going to 4.54 gears, which don’t exist for the 200. You’re correct though, the closest would be you going to 4.10 gears, which do exist.

3.9/3.3 =1.182
4.10/3.3=1.242

4.30/3.9=1.103
4.54/3.9 =1.164 <-
4.88/3.9 =1.251

 

[linuxgod]

We did a couple weeks in Wyoming a couple years back, our 40 LRA tank was clutch.

Supercharger is tempting but I’m just not ready to modify the engine, we only have 40k miles and I’ve not seen a definitive answer on a ECU tune. If we go that route it’s gotta be done flawlessly. Gears, on the other hand, may also be pricey but the downside risks are much less.

We don’t care about MPG, I’m more concerned with converter temps and RPM’s.

Note my trans temps run about 15-20F hotter now. Factory gearing I would run 196-198F when locked in 4th towing going 70-75. Now I run about 215F with the torque converter locked (4th, 5th, or 6th and towing or not towing)

 

[Artie]

Note my trans temps run about 15-20F hotter now. Factory gearing I would run 196-198F when locked in 4th towing going 70-75. Now I run about 215F with the torque converter locked (4th, 5th, or 6th and towing or not towing)

Interesting. I have lots of wiggle room during normal driving. Converter temps crossing Texas running 75-80 are 150°-180°. It’s the climbs and inability to get into and stay in the power RPM’s at 3500. If I could hold revs in 3rd between 3800-4200 it would be great. Currently, it slowly falls until I’m in 2nd and working through 4000 climbing to 5500 then to 3rd which falls low enough that it can’t hold the rpm’s.

I think it was you who told me before I’m a good candidate for gears and supercharging… you may be about to tell me again lol

 

[Hams202]

I am running 8spd. 4.30’s, 34’s

I am also on Harrop. My 200 has been this way since it was nearly new.

With my build, my towing consists of a 26’ trailer pulling a 4-door rzr along with two more four wheelers.

I am able to tow very well in this setup and have been very happy with it for many years now.

I do run a LRA 40 gallon sub tank with my setup.

Around town mileage is 11’s and highway unladen is around 13.

Towing is more like 9.

It pulls really well at 75 no issues.

My only complaint, if I had one, is that first gear is almost unusable as it is so short with this final drive.

I have always wanted to try a 3.90 but it would be a lot of work on a hunch.

Overall, I love it.

35k miles on it in this configuration in the mountains of Colorado. Not a blip.

Chris.

 

[Artie]

I am running 8spd. 4.30’s, 34’s

I am also on Harrop. My 200 has been this way since it was nearly new.

With my build, my towing consists of a 26’ trailer pulling a 4-door rzr along with two more four wheelers.

I am able to tow very well in this setup and have been very happy with it for many years now.

I do run a LRA 40 gallon sub tank with my setup.

Around town mileage is 11’s and highway unladen is around 13.

Towing is more like 9.

It pulls really well at 75 no issues.

My only complaint, if I had one, is that first gear is almost unusable as it is so short with this final drive.

I have always wanted to try a 3.90 but it would be a lot of work on a hunch.

Overall, I love it.

35k miles on it in this configuration in the mountains of Colorado. Not a blip.

Chris.

View attachment 3942518
View attachment 3942517

Your build is very similar to mine, minus the Harrop, and you tow more weight…It sounds like 3.9 will be my sweet spot.

Your MPG’s are practically the same as mine as well, I seems like there is a floor for bad MPG’s and we’ve hit it.

I’ve put supercharging on the shelf for at least until I run out of warranty. I’m at 40k now and doing a suspension refresh and likely gears. Another 50ish will put me near 100k, nearly out of warranty, and just getting the engine broke in… I have a feeling I’ll be eyeing it hard enough to make a move when I refresh suspension again around then.

 

[Hams202]

I should mention I have a pair of 200’s. The one above is my 2019. I also have a 2015 in magnetic that is of a much lesser build.

Normal driving in town, you can’t really tell much of a difference in the two. Where I do notice a big difference is at highway speeds. The Harrop’ed 19 pulls way more efficiently up to speed with more passing power on tap.

If I ever loaded my ‘15 down like my ‘19, I would likely supercharge it too haha!

The other thing I can’t help but observe; I feel the 15 makes better use of its poweband with the 6 speed. The 8 speed loves to shift. The 6 speed lets the engine rev through its powerband. In many ways, I feel like I prefer the power delivery of the 6 speed.

Anyhow - if I was building my 19 again, I would probably go with a 3.90 option. The parts are available via Toyota so you can go 100% OEM. There isn’t a shelf kit but you can source 100% of the parts thru your dealer to do it. I like this a LOT.

- Chris.

 

[Artie]

I should mention I have a pair of 200’s. The one above is my 2019. I also have a 2015 in magnetic that is of a much lesser build.

Normal driving in town, you can’t really tell much of a difference in the two. Where I do notice a big difference is at highway speeds. The Harrop’ed 19 pulls way more efficiently up to speed with more passing power on tap.

If I ever loaded my ‘15 down like my ‘19, I would likely supercharge it too haha!

The other thing I can’t help but observe; I feel the 15 makes better use of its poweband with the 6 speed. The 8 speed loves to shift. The 6 speed lets the engine rev through its powerband. In many ways, I feel like I prefer the power delivery of the 6 speed.

Anyhow - if I was building my 19 again, I would probably go with a 3.90 option. The parts are available via Toyota so you can go 100% OEM. There isn’t a shelf kit but you can source 100% of the parts thru your dealer to do it. I like this a LOT.

- Chris.

Agree on the OEM availability. Cruiser Outfitters sells compete thirds with OEM parts with ARB lockers. If I do this I’ll pony up and go that route and keep my OE stuff to sit on or sale.

My 8 speed likes to shift as well but the pedal commander really takes care of most of that.

Thanks for all the info, it’s really helpful. 2 Cruisers is something we’re aiming for as my wife wants one for her commuter. She thinks we’re crazy so the more people I can point out with multiples makes her feel better. I do the same with garages with lifts… she’s coming around on that as well.

 

[TeCKis300]

So it looks like Santa may come early this year… Christmas in July is still a thing I think.

Anyway, we’re strongly considering making the jump to 3.9’s but I want to make sure I don’t have any blind spots. Here are the issues I want to solve:

1. The power hole I have when doing any mountain passes while towing. The 2nd gear- foot to the floor- 4800 rpm slog while conveyer temps hit 250+

2. The weird space I find myself in on dirt roads while towing where I can’t maintain 45mph + to keep the converter locked up so the temp gets 250+ if I stay in 4 hi. I can get around this by using 4Lo but now I’m maxed out at 30mph but the road is nice enough to go faster.

3. Those interstate drives like Oklahoma or west Texas where it’s flat and windy enough that I can’t stay in 6th gear at 75mph so it drops to 5th and I gain MPG hell for 300 miles.

4. Sometimes a little more engine braking would be nice.

Those are my main complaints given my build weight and all the towing we do (80% of our miles we have the trailer.)

These issues won’t be completely solved with the switch but I expect them to get much better based on all the reading I’ve been doing on here.

What will I be giving up? Will I still be able to run 75-80 mph on the interstate while towing if conditions call for it? I’ve looked at the spreadsheet one of yall posted with gear ratios, rpm, and MPH with 34” tires and it looks like my rpms will be about 500 higher for the same speed or roughly 10mph slower for the same rpms.

What could I be overlooking or not understanding here?

Using the above data and tables here to answer your questions. Short answer is you want 3.9s. It'll be a world of difference between your current setup (yellow) versus 3.9 gears (green) as an 18% overall gearing improvement. You currently have 7% worse gearing than stock baseline which accounts for a lot of the symptoms, whereas you'll have a 9% gearing advantage over stock baseline after regear. The bottom row of the table is key to understand how gearing is relative to OEM. Being as close to OEM as possibly will bring the best balance even for really big tires. 4.1 or 4.3s belong in the realm of rigs aiming for 37s and larger.

1. The power hole will all but disappear as you'll have about 800rpm/40hp more at that same point.
2. With more gearing and torque to the wheels while using the upper gears, it'll have a better chance to lock the converter
3. At 75mph and 6th gear or about 2500rpm, the 5.7L makes less than 140hp. After regear at the same speed will put the engine at 2950rpm with better potential around 175hp, where it's much more likely you can stay in 6th.
4. Yes, much better braking which I almost find more important for heavy towing!

It'll do everything you do now, better. In addition to the power and gearing improvements, shift logic should be appreciably better.

 

[Hams202]

Agree on the OEM availability. Cruiser Outfitters sells compete thirds with OEM parts with ARB lockers. If I do this I’ll pony up and go that route and keep my OE stuff to sit on or sale.

My 8 speed likes to shift as well but the pedal commander really takes care of most of that.

Thanks for all the info, it’s really helpful. 2 Cruisers is something we’re aiming for as my wife wants one for her commuter. She thinks we’re crazy so the more people I can point out with multiples makes her feel better. I do the same with garages with lifts… she’s coming around on that as well.

Heck yeah! I originally bought my 2019 for myself as a DD. My wife and kids loved it so much. I found she started to drive it more and more over her car. Her comment was always along the line that it felt so heavy and safe.

I eventually sold her car and gave her mine. I bought my 2015 as it was too nice to pass up.

I definitely like the idea of OEM. My pinion bearing failed on my rear about 10k miles into the swap. It sounded like a rotor was dragging against a heat shield.

When it was swapped out, I insisted the whole assembly come out and replace with Toyota OEM.

Good luck; I think you will like the truck with new gears a lot.

- Chris.

 

[Artie]

View attachment 3943893

Using the above data and tables here to answer your questions. Short answer is you want 3.9s. It'll be a world of difference between your current setup (yellow) versus 3.9 gears (green) as an 18% overall gearing improvement. You currently have 7% worse gearing than stock baseline which accounts for a lot of the symptoms, whereas you'll have a 9% gearing advantage over stock baseline after regear. The bottom row of the table is key to understand how gearing is relative to OEM. Being as close to OEM as possibly will bring the best balance even for really big tires. 4.1 or 4.3s belong in the realm of rigs aiming for 37s and larger.

1. The power hole will all but disappear as you'll have about 800rpm/40hp more at that same point.
2. With more gearing and torque to the wheels while using the upper gears, it'll have a better chance to lock the converter
3. At 75mph and 6th gear or about 2500rpm, the 5.7L makes less than 140hp. After regear at the same speed will put the engine at 2950rpm with better potential around 175hp, where it's much more likely you can stay in 6th.
4. Yes, much better braking which I almost find more important for heavy towing!

It'll do everything you do now, better. In addition to the power and gearing improvements, shift logic should be appreciably better.

Thanks for the detailed write up and spreadsheet. The numbers are plain as day and don’t lie.

I think it’s time, Santa is coming early this year.

 

[K9LTW]

Using the above data and tables here to answer your questions. Short answer is you want 3.9s. It'll be a world of difference between your current setup (yellow) versus 3.9 gears (green) as an 18% overall gearing improvement. You currently have 7% worse gearing than stock baseline which accounts for a lot of the symptoms, whereas you'll have a 9% gearing advantage over stock baseline after regear. The bottom row of the table is key to understand how gearing is relative to OEM. Being as close to OEM as possibly will bring the best balance even for really big tires. 4.1 or 4.3s belong in the realm of rigs aiming for 37s and larger.

1. The power hole will all but disappear as you'll have about 800rpm/40hp more at that same point.
2. With more gearing and torque to the wheels while using the upper gears, it'll have a better chance to lock the converter
3. At 75mph and 6th gear or about 2500rpm, the 5.7L makes less than 140hp. After regear at the same speed will put the engine at 2950rpm with better potential around 175hp, where it's much more likely you can stay in 6th.
4. Yes, much better braking which I almost find more important for heavy towing!

It'll do everything you do now, better. In addition to the power and gearing improvements, shift logic should be appreciably better.

Great chart! Now...is there a general consensus on what = too MUCH gearing? 32.7s aren't on the part for 3.9s, but it's easy enough to extrapolate. Negating tire/wheel weight and such (just way too many variables), when is it too much? I suppose one's use case would factor into it (e.g. primarily long slogs on interstates vs. slow dirt), but paralysis by analysis is real...at least for me.

 

[Hams202]

Great chart! Now...is there a general consensus on what = too MUCH gearing? 32.7s aren't on the part for 3.9s, but it's easy enough to extrapolate. Negating tire/wheel weight and such (just way too many variables), when is it too much? I suppose one's use case would factor into it (e.g. primarily long slogs on interstates vs. slow dirt), but paralysis by analysis is real...at least for me.

I think use case is big deciding factor here.

The one thing that bothered me with bigger tires at highway cruise was the constant shifting.

Gears definitely alleviate this issue.

To me - the 8spd and 3.90’s are a great option for anything beyond stock OD tires.

 

[Artie]

I think use case is big deciding factor here.

The one thing that bothered me with bigger tires at highway cruise was the constant shifting.

Gears definitely alleviate this issue.

To me - the 8spd and 3.90’s are a great option for anything beyond stock OD tires.

I’ve only been on the interstate a handful of times with out my camper but leaving it in “D” did produce back and forth shifting between 6,7,8. It was wild to hit 85 and it still want to shift down to 7. Otherwise, I stick it in “6” and that’s where I leave it, even without the camper… it’s just habit at this point.

 

[TeCKis300]

Great chart! Now...is there a general consensus on what = too MUCH gearing? 32.7s aren't on the part for 3.9s, but it's easy enough to extrapolate. Negating tire/wheel weight and such (just way too many variables), when is it too much? I suppose one's use case would factor into it (e.g. primarily long slogs on interstates vs. slow dirt), but paralysis by analysis is real...at least for me.

I'd agree there are factors that will drive gearing. But desirable overall gearing will generally be closer to stock than dramatic changes. For example, the Tundra tow package changed factory gearing from 4.1s to 4.3s, or only a 6% change. F150s change from 3.55s to 3.73s, a 5% change.

Obviously, one should correct for tire size. And potentially for factors like installed weight, aero loads with armor and roof racks, elevation, and more specific use cases.

When going from factory 3.307 to 3.9s, it's a huge 18% change. That's enough to take care of most mainstream tire sizes with plenty of additional margin.