Need bigger gears

[DallasTahoe]

I’m currently on a trip through Colorado, and My Girl is really struggling going up the mountains, running at about 2000rpm at around 35-40mph to make it up these mountain passes, she’s just got no ass! I’ve got 3.73 gears and running new 285/75/17 toyo open country A/T so they are right at 33 in tall. What gear ratio should I go with? I’m thinking 4.10’s but maybe a lil more? Keep in mind this is my daily, it’s not a trail rig by any means but may need to haul a trailer, (thinkin about a small to medium travel trailer)


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[454cid]

The first thing that needs to be addressed is the PCM... has it been programmed for the tire size change? I don't know what year truck you have, and I'm kind of assuming the early trucks need to be programmed like the later trucks do. I ran 285/75r16s on my truck.... 245s are stock, and I'm sure it was messing with the shift points. There were times if felt like the transmission was slipping, but as soon as I went back to stock size tires it was fine. I have 4.10's with a 454. but the PCM didn't know about the 285s. 265s didn't seem to bother it. I'd guess that 4.56s may be in the ball park of consideration. Maybe someone else here done the modifications to run the 285s correctly and can tell you better. The tires, I had were used, already so I simply wore them out and moved on. I never tried to solve the issue.

 

[jsfrmsj]

I'm willing to bet the low power your feeling is from the higher altitude of Colorado compared to Dallas. See the video below for an entertaining explanation.

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[DallasTahoe]

I'm willing to bet the low power your feeling is from the higher altitude of Colorado compared to Dallas. See the video below for an entertaining explanation.

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No not really, it was the same in Dallas


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[DallasTahoe]

The first thing that needs to be addressed is the PCM... has it been programmed for the tire size change? I don't know what year truck you have, and I'm kind of assuming the early trucks need to be programmed like the later trucks do. I ran 285/75r16s on my truck.... 245s are stock, and I'm sure it was messing with the shift points. There were times if felt like the transmission was slipping, but as soon as I went back to stock size tires it was fine. I have 4.10's with a 454. but the PCM didn't know about the 285s. 265s didn't seem to bother it. I'd guess that 4.56s may be in the ball park of consideration. Maybe someone else here done the modifications to run the 285s correctly and can tell you better. The tires, I had were used, already so I simply wore them out and moved on. I never tried to solve the issue.

Didn’t think programming it would do anything except adjust the speedo mine is a 1998 GMC Yukon


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[Christian Steffen]

Didn’t think programming it would do anything except adjust the speedo mine is a 1998 GMC Yukon


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Speedometer and shift points. The altitude will definitely make a difference.

285s on 3.73s definitely is going to hurt force to the ground. 4.10s or 4.56 would help a lot.

Maybe try a tune from someone first though, the extra power might be enough to get you by.

Edit: What year tahoe is it?

 

[Elroy]

stock exhaust? original cats? you must replace ! the stock cats can plug up/break down killing your power, the higher it revs the worse it gets, if you struggle without a trailer you will be really screwed with one , i put a magnaflow stainless system w downpipes/cats, a manifold back system, expensive but truck is niight and day better, then a black bear tune, which will help the transmission as well as the fueling, then bilstein shocks, these are the 3 best things i did for towing and just driving in general

 

[RichLo]

It seems everybody goes to re-gearing to solve their problems.

Truck bogging down at high altitudes? re-gear.
Truck backfiring? re-gear.
Male pattern baldness? re-gear.
Erectile dysfunction? re-gear.

Got a case of the Monday's? Re-Gear!

 

[slowburb]

That tire could be close to 34" tall. That effectively changes your gear ratio to around 3.08:1. In and of itself that shouldn't turn your truck into a turd, but mixed with say a gunked up fuel filter, a crudded up air filter, and other possible tune up parts that aren't it great condition (distributor cap, plug wires, etc) I could see it giving you problems.

 

[Jared Jackson]

I would make sure all my systems were up to par before looking to gears for a fix. If it's running like poop, even in Texas, you may have a problem elsewhere...