DIY 4.3 Re-Gear (2 Viewers)

[linuxgod]

I get your point (even as a joke), but counter with this example of me getting in over my head. Almost lost one of my hands in the process. Wouldn't have happened if I didn't have lockers.

Rolling a truck (admittedly out of ignorance and lack of skill) has a way of making you prioritize keeping CoG low.

View attachment 2374583

Ouch! Glad you were ultimately OK.

 

[TeCKis300]

Ooof! That will always put things in perspective.

How lifted was the 4R?

 

[bloc]

Ooof! That will always put things in perspective.

How lifted was the 4R?

It was an 80-series and about 3”. Not especially tall, but the point is anything you do to lift or add weight to the roof makes scenarios like that more likely.

Not to worry.. I eventually got it back on the road with another body.

 

[turbo8]

I'm thinking about doing a rear gear to 4.3. If I find a 3rd member from a 98 to 2002 LC or LX it should work as long as it is a 4.3 ratio, correct? For the front I would need to find a carrier from a 2007 to 2020 tundra with 4.3 ratio? What are the going rates for a good condition used 3rd/carrier?

 

[TeCKis300]

Yes and yes.

Rear Diff
- 4.3 carrier from 98-02 LC or LX. This ratio came from the 4-speed cruisers of the day (03+ got 5-speeds)
- There are factory locked ones available. Comments suggest this could be retrofitted for air actuation. For LX models only that won't have sway bar interference against the actuator.
- Carrier is directly drop into the 200-series
- Note that the 100-series uses a smaller diameter input flange and snout on the pinion shaft. If you're just looking to source the ring and pinion with full size snout, and will rebuild from your current diff, @bloc was able to sleuth a new OEM R&P 4.3 parts kit ( 41201-80493 )
- I sourced mine for $120; $200 shipped

Front Diff
- 4.3 carrier from Tundra or Sequoia. Probably 08-20?*. 4.3s only came on these models with the optional tow package. Look for door sticker axle code B02A. Parts resellers should have the associated VIN which you can check on Toyota website to confirm tow package in options list.
*I don't know that there were absolutely no changes through 2020 that affect fitment on the 200-series. Mine is from a Tundra 2012 that fit fine.
- Fitting a locker to a front clamshell carrier is supposedly no joke with need for special measuring tools for lash. Fortunately if not looking for a locked front axle, it otherwise drops in after changing out the peripheral ADD actuator
- I sourced mine for $175 shipped

 

[turbo8]

Thanks for the clarification.

Since the 100 series uses a smaller input flange and snout, do you recommend swapping these out or should this be fine for a quick swap?

Yes and yes.

Rear Diff
- 4.3 carrier from 98-02 LC or LX. This ratio came from the 4-speed cruisers of the day (03+ got 5-speeds)
- There are locked ones available. Comments suggest this could be retrofitted for air actuation. For LX models only that won't have sway bar interference against the actuator.
- Carrier is directly drop into the 200-series
- Note that the 100-series uses a smaller diameter input flange and snout on the pinion shaft. If you're just looking to source the ring and pinion with full size snout, and will rebuild from your current diff, @bloc was able to sleuth a new OEM R&P 4.3 parts kit ( 41201-80493 )
- I sourced mine for $120; $200 shipped

Front Diff
- 4.3 carrier from Tundra or Sequoia. Probably 08-20?*. 4.3s only came on these models with the optional tow package. Look for door sticker axle code B02A. Parts resellers should have the associated VIN which you can check on Toyota website to confirm tow package in options list.
*I don't know that there were absolutely no changes through 2020 that affect fitment on the 200-series. Mine is from a Tundra 2012 that fit fine.
- Fitting a locker to a front clamshell carrier is supposedly no joke with need for special measuring tools for lash. Fortunately, it otherwise drops right in after changing out the ADD actuator
- I sourced mine for $175 shipped

 

[grinchy]

So it's about $2k for the full package? $400 thirds + $1200 locker + $300 misc parts / seals + time.

 

[TeCKis300]

The snout (where the input flange interfaces) is integral to the 4.3 pinion. Only way to get a full sized one is to use the part number kit above, rather than sourcing from a 100-series.

Other than the input snout and flange, the internals and bearings are all full size to the 200-series. So no concern for power handling or integrity from wheel stresses. Talked to a couple diff shops, they just don't ever see pinion input failures. Unless the very rare case of axle wrap from bad geometry in custom rigs, or rock bashing where anything will fail.

So where I think the larger input snout and flange make a difference is for 200-series that are built to be hardcore rock crawlers that will bash against the drive shaft or diff input flange. That's not me so I'm not particularly concerned.

Left 200-series, right 100-series.

 

[TeCKis300]

Parts references and cost. There's some specialized tools (and tools costs) involved with this operation including press, bearing plate, seal pullers, dial indicator, seal and bearing press dies, resourcefulness. Contracting out the carrier assembly may not be a bad idea and the carriers can be dropped in with relative ease in a weekend and no specialized tools.

Onto costs.

Front diff (~$250, w/o shipping & tax)
1) Used Tundra Carrier Assembly, $175
2) Toyota Red FIPG 00295-01281, $18.91
3) x2 Inner Joint Assembly Snap Ring 90521-37010, $1.27
4) R Intermediate Shaft Output Seal 90311-47013, $14.11
5) L Diff Carrier Output Shaft Seal 90311-47027, $12.97
6) 2 qts Gear Oil
7) Optional Harrop ELocker

Rear Diff w/ rebuild ($400), w/ Locker (~$1650)
1) Used 100-series Carrier Assembly, $120
2) Axle Housing Gasket 42181-60060, $7.83
3) x2 Diff Case Side Bearings 90366-50177, $38.00
4) Rear Pinion Bearing 90366-40111, $58.41
5) Front Pinion Bearing (100-series part) 90366-30071, $38.00
6) Pinion Crush Spacer (100-series part) 41231-60030, $16.27
7) Pinion Seal (100-series part) 90311-38066, $10.33
8) x2 Axle Seal 90310-63001, $9.07
9) x2 Axle O-Ring 90301-88077, $4.13
10) 5 qts Gear Oil
11) Harrop Rear ELocker (I recommend the fine folks at Cruiser Brothers, Georg @orangefj45 )

Rear Axle Hub Bearing (~$900, optional while you're in there. Given the significant costs and ease of pulling axles, I probably should have held this off until it was actually an issue. ~125k miles, mine were drum tight)
1) Right Hub & Bearing 42450-60070, $326.45
2) Left Hub & Bearing 42460-60030, $326.45
3) x2 Axle Seal 90310-63001, $9.07
4) x2 Axle Bearing Retainer 42423-34040, $23.07
5) x2 Axle Bearing Retainer Snap Ring 90520-46014, $2.47
6) Contracted out labor to press and remove $$$

 

[orangefj45]

GREAT THREAD!!!

First and foremost, this thread is exactly what MUD is all about. It’s members taking the time to share information for the better of the community. Big props to you.

Georg @ Valley Hybrids, Cruiser Brothers & Long Range America

 

[TeCKis300]

Feedback from a recent 1400 miles trip with trailer in tow. My above impressions stand that for a lightly built 200-series on 33s, stock 3.9 gearing is just fine.

For context, I weighed in on a CAT scale and my combined rig with trailer is... a fat 14,920 lbs. Gearing overall now is about 3% higher than a stock rig.

Previously, towing this rig with 3.9s and 33s was generally pretty good (7% gearing loss relative to stock). Better than good. The case where it wanted more gear was take-off from a standstill on grade and/or elevation. In sunny socal, I often camp in the mountains so it was something worth addressing. At really high elevations (>6k) and grade (>7%), I had a hole in the powerband at around 25-30mph where I couldn't access peak power @5600rpm. Too fast for 1st, I'd be stuck in 2nd gear @4,000 rpm. 4.3s made a huge difference here as I had access again to climbing power and acceleration in those extreme situations. 4.3s do also improve around town tractability with this much weight. Not as much performance impact at freeway speeds but hold that thought.

What's even a bigger difference is the enhanced engine braking. On steep grades, requiring 2nd gear engine braking, I often had to manage speed with firm applications of brakes at intervals. On particularly long stretches, this can be precarious as it really takes awareness and management to not allow too much heat to be built up in the brakes, less it feels like a runaway freight train with faded brakes. I've faded the trailer drum brakes before. I use upgraded pads on my stock brakes and fortunately, the 200-series has reasonably solid brakes. Not recommended, but I sometimes resort to using higher speeds downhill to allow aero drag to absorb a portion of the kinetic energy. With the 4.3s, engine braking has increased tremendously that it can just about hold speed indefinitely.

Engine braking for heavier rigs may just be the stronger case for re-gearing as I find the 5.7L engine to be pretty flexible. It's not like Taco's and other weaker trucks, as the 5.7L is such a brute even without optimal gearing.

Freeway MPG efficiency with trailer in tow - this is an interesting area as it wasn't necessarily an improvement. Previously, with 3.9s and 33s, for my rig and its weight and aero, the preferred cruise gear was 4th, putting me at ~2500 rpm at ~65mph. Note with 33 tires, 4th works out to be about an ideal 4.5 gear. This worked great with enough margin to lockup the torque converter, and still handle slight grades and wind. With the re-gear at 65mph, it puts things a bit too high and too low. 4th is now too high at 3k rpm with more gearing (windage losses) than I need to cruise. 5th is barely workable and will just lockup the torque converter on flats, with RPM a bit low at ~2150 rpm. So while pulling on hills improved, cruise is now a bit more inefficient with ~.5mpg loss.

This was all a plan to move up to 35s however, which should keep some of the benefits of hill performance, and improve cruise gearing.

200-series continues to earn its keep. Wouldn't have anything else with its unique mix of capacity, stability, comfort, and capability.

 

[Artie]

Feedback from a recent 1400 miles trip with trailer in tow. My above impressions stand that for a lightly built 200-series on 33s, stock 3.9 gearing is just fine.

For context, I weighed in on a CAT scale and my combined rig with trailer is... a fat 14,920 lbs. Gearing overall now is about 3% higher than a stock rig.

Previously, towing this rig with 3.9s and 33s was generally pretty good (7% gearing loss relative to stock). Better than good. The case where it wanted more gear was take-off from a standstill on grade and/or elevation. In sunny socal, I often camp in the mountains so it was something worth addressing. At really high elevations (>6k) and grade (>7%), I had a hole in the powerband at around 25-30mpg where I couldn't access peak power @5600rpm. Too fast for 1st, I'd be stuck in 2nd gear @4,000 rpm. 4.3s made a huge difference here as I had access again to climbing power and acceleration in those extreme situations. 4.3s do also improve around town tractability with this much weight. Not as much of an impact at freeway speeds.

What's even a bigger difference is the enhanced engine braking. On steep grades, requiring 2nd gear engine braking, I often had to manage speed with firm applications of brakes at intervals. On particularly long stretches, this can be precarious as it really takes awareness and management to not allow too much heat to be built up in the brakes, less it feels like a runaway freight train with faded brakes. I've faded the trailer drum brakes before. I use upgraded pads on my stock brakes and fortunately, the 200-series has reasonably solid brakes. Not recommended, but I sometimes resort to using higher speeds downhill to allow aero drag to absorb a portion of the kinetic energy. With the 4.3s, engine braking has increased tremendously that it can just about hold speed indefinitely.

Engine braking for heavier rigs may just be the stronger case for re-gearing as I find the 5.7L engine to be pretty flexible. It's not like Taco's and other weaker trucks, as the 5.7L is such a brute even without optimal gearing.

MPG efficiency with trailer in tow - this is an interesting area as it wasn't necessarily an improvement. Previously, with 3.9s and 33s, for my rig and its weight and aero, the preferred cruise gear was 4th, putting me at ~2500 rpm at ~65mph. Note with 33 tires, 4th works out to be about an ideal 4.5 gear. This worked great with enough margin to lockup the torque converter, and still handle slight grades and wind. With the re-gear at 65mph, it puts things a bit too high and too low. 4th is now too high at 3k rpm with more gearing (windage losses) than I need to cruise. 5th is workable and will just lockup on flats, with RPM a bit low at ~2150 rpm. So while pulling on hills improved, cruise is now a bit more inefficient with ~.5mpg loss.

This was all a plan to move up to 35s however, which should keep some of the benefits of hill performance, and improve cruise gearing.

200-series continues to earn its keep. Wouldn't have anything else with its unique mix of capacity, stability, comfort, and capability.
View attachment 2408743

Thanks for this detailed post, it’s very informative. I’ve been curious about towing at altitude both on and off road. My weight will be less than yours, maybe 10-11k with my camper and running 34’s. I may be ok with the stock gearing, you think?

 

[linuxgod]

MPG efficiency with trailer in tow - this is an interesting area as it wasn't necessarily an improvement. Previously, with 3.9s and 33s, for my rig and its weight and aero, the preferred cruise gear was 4th, putting me at ~2500 rpm at ~65mph. Note with 33 tires, 4th works out to be about an ideal 4.5 gear. This worked great with enough margin to lockup the torque converter, and still handle slight grades and wind. With the re-gear at 65mph, it puts things a bit too high and too low. 4th is now too high at 3k rpm with more gearing (windage losses) than I need to cruise. 5th is workable and will just lockup on flats, with RPM a bit low at ~2150 rpm. So while pulling on hills improved, cruise is now a bit more inefficient with ~.5mpg loss.

Interesting.

Would you mind running at 70-75MPH and let me know the impact to MPG? That's where I notice it the most

Seriously though doing the math that makes sense given the gear ratio and RPM. I do find >65mph I sometimes end up leaning into the skinny pedal a bit to maintain my speed where I don't normally feel like I should need to do so, but I know CA has very low speed limits for those pulling a trailer. (Conversely if you've ever driven through the stretch of I-80 in Nebraska between Lincoln and Grand Junction you'll know why 65 isn't nearly fast enough)

 

[TeCKis300]

Thanks for this detailed post, it’s very informative. I’ve been curious about towing at altitude both on and off road. My weight will be less than yours, maybe 10-11k with my camper and running 34’s. I may be ok with the stock gearing, you think?

With less overall weight but taller tires, I think your experience will be much like mine with stock gears. That's to say I think it'll do great. Though report back and let us know what you think.

I had my first experience towing at 7k feet over some ridiculously narrow, off camber, and steep grades of a campsite. It's one of those hills you look at, then look at your trailer, and back, and think...hmmm. Thank goodness for low range. It affords a measure of control and torque that's just what's needed for the job.

Interesting.

Would you mind running at 70-75MPH and let me know the impact to MPG? That's where I notice it the most

Seriously though doing the math that makes sense given the gear ratio and RPM. I do find >65mph I sometimes end up leaning into the skinny pedal a bit to maintain my speed where I don't normally feel like I should need to do so, but I know CA has very low speed limits for those pulling a trailer. (Conversely if you've ever driven through the stretch of I-80 in Nebraska between Lincoln and Grand Junction you'll know why 65 isn't nearly fast enough)

I do tow into the 70-80mph regularly and she's stable and great at that speed. Trying to conserve fuel as it costs me over 30 miles range per tank (low to mid 8mpg) maintaining a higher speed. Ideally try to keep 10mpg keepign about 68mph. Fast enough but not too fast to break the 15mph over threshold (55mph speed limit for towing in CA) if I were to get a ticket.

It seems to be the same story with gears. 4th still spins more rpm than necessary (windage losses). 5th too little rpm and likely getting into the rich fueling/load range to maintain enough power with good efficiency to keep the rig going. You have larger tires than my current 33.2" tires, which may shift things just enough for you. I think with an upgrade to 35s, that it'll give me closer to that magic 4.5 gear again.

This table from this thread may help find that magic combo. Every rig tire/trailer/weight/aero will be different. Shows where the 8-speed really excels as it has more gear ratios to get that optimal rpm.

 

[linuxgod]

I do tow into the 70-80mph regularly and she's stable and great at that speed. Trying to conserve fuel as it costs me over 30 miles range per tank (low to mid 8mpg) maintaining a higher speed. Ideally try to keep 10mpg keepign about 68mph. Fast enough but not too fast to break the 15mph over threshold (55mph speed limit for towing in CA) if I were to get a ticket.

It seems to be the same story with gears. 4th still spins more rpm than necessary (windage losses). 5th too little rpm and likely getting into the rich fueling/load range to maintain enough power with good efficiency to keep the rig going. You have larger tires than my current 33.2" tires, which may shift things just enough for you. I think with an upgrade to 35s, that it'll give me closer to that magic 4.5 gear again.

This table from this thread may help find that magic combo. Every rig tire/trailer/weight/aero will be different.

Thanks. This is all helpful, and really I'm probably being too analytical about it because I don't yet have the $ to pull the trigger. Hopefully this winter...

Yeah I have larger tires (33.8"), plus the winch bumper, plus a roof rack crammed with crap, so I definitely take an aero hit too. I mentally debated 4.30 vs 4.88 a few times, as 4.30 is a spot-on RPM match when on 34s and every time I look at that table I see too much gear in 4th. But then aero, weight, etc and I suspect 4.30s would be better but still lacking at times. Really I just want more get-up-and-go merging on the highway or towing in the mountains (as you know the ratio between 2 and 3 is just too wide) and something that'll keep my gas mileage from being utter crap when towing (I normally get about 7.5 MPG maintaining 72-75 which I'm OK with, but sometimes I get a few tanks where I'm getting maybe 6 MPG. So hearing your first-hand MPG experience is helpful.

It's a pity Toyota doesn't make a 3 speed transfer case that has high range, low range, and a towing gear which is ~15% taller than high.

 

[TeCKis300]

For your situation and build, and your preferred cruise speed, 4.88s may be the better choice. It should hopefully allow you to grab 5th, spinning ~2700rpm @ 75mph.

With 4.3s, you'll be spinning a few hundred rpm more in 4th at cruise, likely unnecessarily, with no hope of grabbing 5th. With 4.88s in 5th, it'll be a few hundred rpm lower than your cruise rpm today in 4th. Your aero is different than mine - do you think a few hundred rpm less is something it will tug? It may be a good sweet spot. There's a risk that if you can't grab 5th, then you'll be stuck about 600rpm higher than you are now, and loosing cruise efficiency.

With either 4.3s or 4.8s, you will have way better around town tractability. My lowest MPGs prior were stop and go, or around town, as the engine needs to work hard immediately off the line without enough gearing.

 

[linuxgod]

For your situation and build, and your preferred cruise speed, 4.88s may be the better choice. It should hopefully allow you to grab 5th, spinning ~2700rpm @ 75mph.

With 4.3s, you'll be spinning a few hundred rpm more in 4th at cruise, likely unnecessarily, with no hope of grabbing 5th. With 4.88s in 5th, it'll be a few hundred rpm lower than your cruise rpm today in 4th. Your aero is different than mine - do you think a few hundred rpm less is something it will tug? It may be a good sweet spot. There's a risk that if you can't grab 5th, then you'll be stuck about 600rpm higher than you are now, and loosing cruise efficiency.

With either 4.3s or 4.8s, you will have way better around town tractability. My lowest MPGs prior were stop and go, or around town, as the engine needs to work hard immediately off the line without enough gearing.

Non-towing we're almost all around town driving, so that would be a plus. I seem to get about 9 MPG in the city. Granted that's full-on city driving, but still... oof. Highway without the trailer is about 15 MPG if I average ~65, but I lose about 1 MPG per 5 MPH above that right now.

I doubt I'll be able to run in 5th, unless I'm on very flat lands. 4th is OK now most of the time on 3.90s when it's flat, except for times when the ECU seems to be muddying up the timing and I feel I need to push into the gas to maintain >65. You're correct, on 4.88s with 34s I'll be about 300-350 RPMs higher than on 3.90s with OEM 31s, which is kinda the concern. OTOH I have much less aero than you and I'm *hoping* that less skinny pedal effort to maintain highway speeds when towing will offset the higher RPMs - watching my OBD Fusion setup I've found MPG suffers quite a bit when I'm heavy into the gas but still in 4th gear, though not as much as dropping into 3rd (e.g. 7.5MPG light on the throttle in 4th, 5.5-6MPG if heavy into the throttle, and 3-4 MPG down in 3rd).

OBD Fusion gauges have been really interesting to watch, though I'm not entirely sure what I should be seeing sometimes. A/F Commanded and A/F Actual normally sit around 14.5-14.6 but they do get down to 12.5 or 13.5 particularly when I feel like the engine is backing off the timing. I don't have pics from my trip but IIRC knock correction was always around -3 degrees but the ignition advance was around -24-27 degrees when it was acting as expected and down in the -13 to -18 range when MPG was suffering and maintaining 70 was impossible without using 3rd.

This is definitely one of those mods I wish was easy to try out for a bit.

 

[linuxgod]

BTW sorry to hijack your thread. This has been great to read/watch. I'm very impressed by your ability and willingness on this one. I can swap a UCA or add a diff drop, but gear changes are well beyond my skills

 

[TeCKis300]

No hijack at all and happy to move the platform forward with shared knowledge.

OBD Fusion gauges have been really interesting to watch, though I'm not entirely sure what I should be seeing sometimes. A/F Commanded and A/F Actual normally sit around 14.5-14.6 but they do get down to 12.5 or 13.5 particularly when I feel like the engine is backing off the timing. I don't have pics from my trip but IIRC knock correction was always around -3 degrees but the ignition advance was around -24-27 degrees when it was acting as expected and down in the -13 to -18 range when MPG was suffering and maintaining 70 was impossible without using 3rd.

I don't have a monitor on my LX as I do in other cars, but those numbers you offered are pretty good indicators of various things I'm pretty familiar with. If I may...
- A/F ideally is stoichiometric at ~14.7:1. That's where you're going to see the highest efficiency. Anytime it goes to ratios below that, all the way to super rich ratios of 10:1, is when engine load is too high, and the ECU is using fuel to cool the combustion chamber.
- More ignition advance (more negative number) is generally higher efficiency. There's the element of VVTi cam phasing, that is either clocked for efficiency or power. When you're seeing timing advance go down, it's probably when the ECU is responding to load demands and changing cam phasing for power. Dropping to 3rd, even though it has higher windage losses, may be more efficient as the engine can go back to stochiometric ratios and more efficient cam overlap positions.

 

[Dixon Santana]

Gotta say thanks for the write-up! I just finished the swap to 4.3 diffs and 34s are much easier to turn now. For me a simple third member swap was all I did, no real need for a locker at the moment. The only part I struggled with was reinstalling the front diff, it's a tight area. Well worth the effort and if you are patient, fairly cost effective in my opinion.