ucw458

For starters the truck in question is a 90 4Runner, lifted, SAS, 4.88s 35x12.5s, rebuilt 3.0, manual trans, injector upgrade, timing bumped.

The consensus online seems to be that 4.88 gears are perfect for 35" tires. That may be the case at sea level, but I live at 6,000 feet. The places I take this rig to are near 10,000 feet and sometimes higher. The engine runs great and it accelerates fine in the lower gears. But I really have to get on the gas to maintain a reasonable highway speed. And the higher I climb the less useful 4th gear gets. The previous engine had 80 psi compression so it was pretty worn out. The new engine has helped but not as much as I thought it would. When I lived closer to sea level I had a dually 1 ton pickup with a service body and a 3.0. It had plenty of power for highway cruising. I know people are gonna say why didn't you do a motor swap. I thought about it but I wanted a bolt in solution.

Changing gears from 4.88 to 5.29 is only an 8.4% increase in TQ to the wheels. Would that be enough to make it a better on the highway or would it be not enough to justify the cost? Does anyone here have personal experience with 4.88vs5.29 at high altitude?

RJR

Are you talking about high altitude performance on level roads, or going up hill? Around here, pretty much any road above 8000 feet is either going uphill or downhill pretty significantly. I have 33 inch tires with 4.56 gears, which is essentially the same numerical tire/gear ratio as you have. Going up a 6% grade at 8-10,000 feet requires 3rd gear, no way around it. I don't think an 8% gear change would change that - you'd just be going 8% slower at the same rpm. 4th to 3rd is a 44% gear ratio change, so unless you could regear to get about a 20% change to split the difference (which would require a 5.85 gear set in your case), I don't think you'd be happy with the results.

ucw458

I know uphill performance will require more hp. It makes it over the passes in 3rd. Which is acceptable considering my 2wd 22re pickup requires the same gear. The new engine is alot better. I should be able to get up to Antero in 2wd now. I just wish it was a little better around town or on slight highway inclines. I wanted to do a 1.9 diesel swap but I didn't have the time and budget. Plus finding donor cars here in the mountains is tough.

RJR

At 5000 feet, where I live, there is a long ~4% grade on the interstate nearby. FWIW, I can easily hold 70mph on that grade in 4th gear, and almost do it in 5th.

akwheeler

If you regear keep in mind that if yours came from the factory with 4:88 gears you won't be able to just change the ring and pinion. At least the was the case with my 1995 4runner. Check out my build thread to see the difference in the internals, no after market parts bolt in and nothing in the online ordering process will clue you into this.
I'm at sea level with a 3.0 and 5:29 gears with 37 inch boggers and I am still looking to do the 3.4 swap due to lack of power. It won't accelerate on the highway on even slight hills and will lose speed considerably on anything steeper.

ucw458

This wasn't a 4.88 factory truck. It already has lockers front and rear so re-gearing shouldn't be an issue. But thanks for the heads up on that. I wasn't aware of that issue.

Well it seems by the responses that 5.29s wont make much difference. Kinda wish I had done a swap instead. But live and learn. At least it runs better for now.