Looking a regearing my D1 w/ r380. Currently running 235/85r16 with no plans to go bigger. Truck also has a r380. So the real question is how miserable are 4.11s on the highway? I do quite a bit living in Texas. I see no reason to pass on them for the 3.90 unless it is just miserable on long trips.
3.90 vs 4.11 - Opinions?
- Thread starter _ExpeditionMan
- Start date
Are the 3.90 free and already set up in two 3rd members? 4.11 would be out of the question unless you're going to 35's, if you're going to keep your current tire size the 3.90 could work but why go through all the work for such little change?
Adding truetracs is a possibility. Lowering the gearing offers a substantial improvement in low range when wheeling with a R380. I've read 4.11s were pretty common with ~31/~32s
4:11 would be too low for that size tire. I have 8.25R16 (over 33") Michelins on my D90 with 4:11s and I think its too low. I can't remember exactly, but I'm at like 3k rpm doing 70mph.
Yeah. Stock gearing worked fine for me in a 98 DI with 235/85s. Worked in Colorado, Delaware, and Mississippi. Stock was acceptable for 285/75. When I did 255/85 and switched to 4.11 it was an amazing experience. 4.11 with 235/85 or even 3.9 would be way to short gearing.
It is exactly what I run in the D1 - 3k RPM at 70 mph - with 7.50-16s, stock axle gearing and 1.4:1 high range LT230. Overall, my gas mileage has not changed a bit - it's been very close to 14 mpg average, but going up the grades between Sierras and Rockies is so much more pleasant.
Depending on what the maintainence history is for your engine, around 165K is the mileage when both my V8 engines needed rebuilding. The P.O.s never kept service records, so I'm sure neither went in for the scheduled fluid change and when they did, who knows what oil they used. Probably some Jiffy Lube 30W whenever they remembered.
I’m glad for everyone’s feedback. Definitely reevaluating the decision. Would probably go with 3.90s if I do re-gear based on the evidence here.
Haven't checked it since the head gasket job last year. I have a spare 4.0 GEMS from an identical 96 that I eventually want to pull and rebuild. But that is far out in the future.
I you ARE going to rebuild it, make sure you have the top hat liners installed - properly, from someone who knows what they're doing, not Skeeter's Machine Shop down the street. No offense to Skeeter, but you know what I'm sayin'.
Keep in mind that GEMS (especially early) engines had far fewer cylinder liner failures than Bosch D2 ones.
I’m on a similar boat. Debating between 4.10 and 4.37. I use this formula to solidify decision if I ever make one.
Rpm= (mph x gear ratio x 336)/ tire size
Current: 2601= (70 x 3.54 x 336)/ 32
Rpm. Mph. Gear. Tire
4.10: 2755= (70 x 4.10 x 336)/ 35
4.37: 2936= (70 x 4.37 x 336)/35
Rpm= (mph x gear ratio x 336)/ tire size
Current: 2601= (70 x 3.54 x 336)/ 32
Rpm. Mph. Gear. Tire
4.10: 2755= (70 x 4.10 x 336)/ 35
4.37: 2936= (70 x 4.37 x 336)/35