Regearing with an H55F: 4.11 and lower (1 Viewer)

[HemiAlex]

Let me start off by saying I love my 3.70 gears and the 5 speed. It's a great combo for flat Houston Texas. I can keep pace on the highways with ease, and for the most part I can drive it like a normal vehicle. But the truck is tired and while hotrodding the 2F is in my future....thats not a priority. I don't want to take the truck down for a rebuild right now. It's slow, but that's to be about as expected as an elephant being large.

I've got 32.5" tires in 255/85r16. They work well. I recently drove 3000 miles from Houston to Aspen, wheeled and drove home without issue, but there were some portions where it was completely gutless uphill. I've got 4.11 centersections from a 62 to refresh and put an airlocker into, so that's my base starting point. I want to add a second battery, sliders and drawers in the near future and I really don't want to drag it down any further with more weight unless I add gearing. Also, it works off road but I really want the 4.11 gears for long steep off road descents to keep the truck stable.

So, I want to explore 4.11 to 4.56 gears.....for those that have done this with a 5 speed, did it put the cruising RPM into a place that allowed you to hit long grades with a little bit more speed and power?

I don't mind running it at 3,000 rpm @ 70-75 mph. I feel that if I had 300-500 rpm more in 4th and 5th that the truck would be a lot happier.

 

[mano002]

My BJ60 has 33x10.5 (which measure about 31" tall) with 4.11s and an H55. The speedmeter is back to being correct. 120kmh (75MPH) at about 2800prm. I actually miss the big-tire overdrive and look forward to moving up to 255/85r16 soon. I think the 3B doesn't rev as high as the 2F though.

 

[HemiAlex]

My BJ60 has 33x10.5 (which measure about 31" tall) with 4.11s and an H55. The speedmeter is back to being correct. 120kmh (75MPH) at about 2800prm. I actually miss the big-tire overdrive and look forward to moving up to 255/85r16 soon. I think the 3B doesn't rev as high as the 2F though.

Great info.

I definitely felt the difference going from my 31.25" BFG K02 to these current KM3. I ran them at 45psi on this trip back and it did change the cruise RPM a bit. I ran the truck at 3250-3500 as needed through some of the long mountain passes and it didn't overheat or miss a beat, I've heart the 3B is a bit more challenging to drive.

I feel like I'm a bit off RPM wise from that the truck wants. I'd like to imagine that keeping the RPM low would yield better efficiency, but I think that keeping the RPM up while staying out of the secondary of the carb is the trick. I was able to drive 65mph on the way up there, maybe 2200 rpm out of secondary and I got 16.5 mpg on multiple fill ups. It amazed me. I was in a hurry with the pedal to the floor on the way back and got. 13.4mpg while fighting a head on wind. I stayed in 4th and ran it out, foot to the floor to keep speed.

 

[mattressking]

When you were at altitude did you adjust timing to aid? Truck is going to be pretty weak at 12k with a carb'd 2f, but I was actually fine the entire time with 3.7s, h55 and 35s. Not that I wouldn't desire more power, but I navigated no problem this time. @John McVicker and I seemed to do just fine and his is pretty heavy compared to mine, granted tire variance.

Bumping to 4.56 wouldn't be bad with your setup using the calculator below. Should get you into better powerband that you desire if you don't mine losing some of the top end.

Gear Ratio Calculator

 

[OSS]

In my opinion, the torque curve is wrong running 31" tires, 3:70 gears and any transmission behind the 2F.
The only reason I never installed 4:10 diff gears is because I could never justify the cost.

I remember the sensation of driving my 60 when I just got it (30 years ago) all stock with 28" tires (225/75R-15) and stock suspension. It was FUN to drive. I remember that clearly. I also remember that when I put on 31" tires, it looked more macho (which I liked) but drove worse (on pavement) except when cruising at high speed on the freeway.
I couldn't run dinky 28" tires offroad, so I had to get the bigger 31s, but the cruiser definitely drove a lot better except on the freeway with the little tires. Little tires are just like running 4:10 gears

 

[HemiAlex]

When you were at altitude did you adjust timing to aid? Truck is going to be pretty weak at 12k with a carb'd 2f, but I was actually fine the entire time with 3.7s, h55 and 35s. Not that I wouldn't desire more power, but I navigated no problem this time. @John McVicker and I seemed to do just fine and his is pretty heavy compared to mine, granted tire variance.

Bumping to 4.56 wouldn't be bad with your setup using the calculator below. Should get you into better powerband that you desire if you don't mine losing some of the top end.

Gear Ratio Calculator

My complaint isn’t off road, it’s at altitude on long hills on road. I didn’t bump the initial timing this time. I just tee both my advance pods together at 4,000 ft and run it. I had 15in of vacuum up there, at sea level I’ve got 20in.

It went to 13,900 with no issue in low range. I would like the gearing purely for control off road in that regard.

I’ve resigned to the fact that the truck likes 70 mph as a comfortable speed. Brakes and suspension feel confident there. I don’t need to be pushing it at 80 with the 3.70 gears any more. It takes too much pedal to keep those speeds.

 

[HemiAlex]

In my opinion, the torque curve is wrong running 31" tires, 3:70 gears and any transmission behind the 2F.
The only reason I never installed 4:10 diff gears is because I could never justify the cost.

I remember the sensation of driving my 60 when I just got it (30 years ago) all stock with 28" tires (225/75R-15) and stock suspension. It was FUN to drive. I remember that clearly. I also remember that when I put on 31" tires, it looked more macho (which I liked) but drove worse (on pavement) except when cruising at high speed on the freeway.
I couldn't run dinky 28" tires offroad, so I had to get the bigger 31s, but the cruiser definitely drove a lot better except on the freeway with the little tires. Little tires are just like running 4:10 gears

I feel like the 4.11-4.56 gearing having the feel of stock, while the big tires help me clear obstacles would be great. And I’d still have 5th gear.

I want to keep it slow and make the 2F feel a lot happier.

 

[AussieHJCruza]

H55, 4.11 and 33ish tyres is spot on imho.

 

[The Machinist]

In my opinion, the torque curve is wrong running 31" tires, 3:70 gears and any transmission behind the 2F.
The only reason I never installed 4:10 diff gears is because I could never justify the cost.

I remember the sensation of driving my 60 when I just got it (30 years ago) all stock with 28" tires (225/75R-15) and stock suspension. It was FUN to drive. I remember that clearly. I also remember that when I put on 31" tires, it looked more macho (which I liked) but drove worse (on pavement) except when cruising at high speed on the freeway.
I couldn't run dinky 28" tires offroad, so I had to get the bigger 31s, but the cruiser definitely drove a lot better except on the freeway with the little tires. Little tires are just like running 4:10 gears

I would second this.

Every two years I throw on a pair of ~29" junkyard wheels and tires to go pass emissions testing here in California. Despite looking goofy with 33s in the front and 29s in the back, it drives so much better; it actually makes the 2F fun to drive. Correct gearing is everything with low output motors.

 

[iCruiser]

I last couple years I have upgraded individually to 33" BFGs, H55 then added 4.11s. Installed a diff from a 62 in the front and had back pumpkin rebuilt with an ARB locker. I did notice a significant difference with the lower gearing especially accelerating and going up hills. Still cruises easily at 75mph highway running around 2,600 RPMs. That's as fast as I care to go. Haven't been off-road with this combo yet but can tell it will be better suited for the trails.

 

[FJ60Seth]

I’m running 35” tires with an h55f and 4.11 diffs. I feel like the truck is geared a bit high. 5th gear feels right at about 2500 RPM which puts my speed at 75 MPH, per GPS, on the flats. That’s faster than I prefer cruising on a busy highway with my 500 mile stopping distance. Also steep grades have me crawling in 3rd gear, I can’t quite get into 4th. Speedo is 10% over. 4.11 is tolerable but I think 4.56 would be perfect. I’m sticking with 4.11’s though because they’re easy to find and I’ve a spare one. I’m also dreaming about a Diamond front axle & 4.11 is the max gear they’ll accommodate.

 

[MarkBC]

I’m running 35” tires with an h55f and 4.11 diffs. I feel like the truck is geared a bit high. 5th gear feels right at about 2500 RPM which puts my speed at 75 MPH, per GPS, on the flats. That’s faster than I prefer cruising on a busy highway with my 500 mile stopping distance. Also steep grades have me crawling in 3rd gear, I can’t quite get into 4th. Speedo is 10% over. 4.11 is tolerable but I think 4.56 would be perfect. I’m sticking with 4.11’s though because they’re easy to find and I’ve a spare one. I’m also dreaming about a diamond front axle & 4.11 is the max gear they’ll accommodate.

That's good to know. I'm putting on 80 axles which are 4.10. So with my H55F that means 33" tires should be about right. I want something a bit bigger for off road capability but don't want it under geared. I was thinking about 35".

 

[HemiAlex]

This was all she had. I was truly one with the semi trucks.

The 2F is running great and doesn’t mind being wrung out hard.

If I had more gear, I could have run the pass in 3rd and had a little more speed.

 

[60Works]

There is no rule that says you have to be able to run hills in 5th gear. 4th in an H55F is the same as 4th in an H42.

Gear for where you drive the most. Downshift for the rest.

More than 3,200 rpm is hard on a 2F. Yes it will do it but it won't last as long.

33's with 4.11's is a tried and true combo. 31's with 3.70's is a tried and true combo. 33's with 3.70 is a little tall. 31's with 4.11's is too short.

Its a bit of work, but not too bad, to temporarily install the 4.11 diff into your rear axle. Drive it for a few days. You will almost immediately know what you want.

 

[ProwlerDriver]

I’m debating this exact same issue with my Cummins b3.3. 255 85 r16s. I have 3.7 gears and I currently get 28mpg. But I’m literally going 35mph through the mountains... the power band on this Motor is 1900-2200 with it governed around 2.8k and a redline of 3k. I’m curious the effect of 4.11s on it or if that’s too low with my current rpms

 

[AussieHJCruza]

I’m debating this exact same issue with my Cummins b3.3. 255 85 r16s. I have 3.7 gears and I currently get 28mpg. But I’m literally going 35mph through the mountains... the power band on this Motor is 1900-2200 with it governed around 2.8k and a redline of 3k. I’m curious the effect of 4.11s on it or if that’s too low with my current rpms

What transmission are you running? What RPM at cruise? I would say it probably wants less gear rather than more, but may not have the horses to turn a 3.5 or similar.

 

[ProwlerDriver]

What transmission are you running? What RPM at cruise? I would say it probably wants less gear rather than more, but may not have the horses to turn a 3.5 or similar.

sorry I’m in the H55 camp as well. Cruise at 2000ish. It feels great on the flat, the hills are just slow. But I can cruise at 70 on freeway. I know I can’t have it all just trying to figure out the best combo

 

[MoaByte]

4th in either trans is 1:1. H55 has lower 1st and 5th would be an overdrive. Swap the 3.70's for 4.10's you get much more torque in first, 4th is a couple hundred rpm higher at 75 mph and sliding into 5th will drop you a couple hundred rpm less than 75 was with 3.70's. (talking 33" tires)

 

[HemiAlex]

There is no rule that says you have to be able to run hills in 5th gear. 4th in an H55F is the same as 4th in an H42.

Gear for where you drive the most. Downshift for the rest.

More than 3,200 rpm is hard on a 2F. Yes it will do it but it won't last as long.

33's with 4.11's is a tried and true combo. 31's with 3.70's is a tried and true combo. 33's with 3.70 is a little tall. 31's with 4.11's is too short.

Its a bit of work, but not too bad, to temporarily install the 4.11 diff into your rear axle. Drive it for a few days. You will almost immediately know what you want.

Completely never expected to go up hill in the highway in any gear past 4th. 3rd is my goal.

The truck has 325k on it. 300k of which were with an h42f. 279k with stock tires so it’s seen some rpm in its life. If it was going to die, it would have done it all ready. I’m not worried about the rpm.

I think rebuilding the 4.11 chunks is a good start. I also found that nitro gear offers a 4.30 gear for the 9.5” axle. That’s a good compromise.

 

[cruisermatt]

4.30 gear for the 9.5” axle. That’s a good compromise.

that's only for 100 series carriers