Gear Ratio Change

gsp473 · October 15, 2002

I am considering changing the rear axle gear ratio in my 2000 GMC 1500 2WD with 5.3 V-8. I have the 3.42 gears in it from the factory and when I tow my fifth wheel camper it some times has to work too hard going up hills. I am considering 3.73 or 4.10 rear end and I want to know what else will have to be changed, such as computer, speedo, etc. Also can I get these parts off of another truck with same setup?

Also are the bearings in a 2500, 3500 or HD rear end heavier duty and are the axle housings themselves interchangeable?

Can anyone tell my what trailer weight I may be able to carry with these changes.

Shaners · October 15, 2002

I'm assuming you have an excab shortbed... but the other cab/bed combos are within a few hundred pounds.

ratio 3.42 = 7300 lbs

ratio 3.73 = 8300 lbs

these numbers are the max weight for a fifth wheel trailer. If your trailer is near this weight you are more than likely over loaded as cargo/passangers/beer have to be added/subtracted from those numbers.

They don't list a 4.10 ratio for a 2wd truck.

A dealer should be able to reprogram your computer/speedo to accept 3.73 gears. I don't know if he can program 4.10 gears into a 2wd truck...

Dihappy · October 15, 2002

A dealer may reprogram for you since many trucks do come in 3.73 and 4.10 gears.

I used a HyperTech programmer to program my 4.56's and larger tires as well as other modifications, but that costs about $200-$300

gsp473 · October 15, 2002

Yes 2WD Ext. Cab short bed. I found the weight limits but not for 4.10 ratio. I assume that it can be done but I want to be sure that I can program and if anyone has a gas mileage idea it would be helpful.

I hope to see if a chip from a Z71 with 4.10 gears will work.

dmdbit · October 15, 2002

I changed from 3.42 to 4.10 in a 2wd ext. cab.I used a hppIII to calibrate the speedo.My mileage empty only changed by 1mpg.It stayed the same towing a 6700lb. trailer.It did make a huge difference in the way it handled the weight.

mike b

Shaners · October 15, 2002

An excab shorty 4x4 with the 5.3L and 4.10 gears is rated to tow a 9000 lb five'r. This info was pulled out of a Silverado Brochure.

gsp473 · October 16, 2002

Thanks for all the great info guys. I think I may try the 4.10 and HPP3. I'll keep you posted. :thumb:

GREGGO · October 16, 2002

If you have 3.42's now, did your truck come with the towing package? G80 locker? I went from 3.42's to 3.73's with an Auburn posi on my truck. It did make a huge difference. Not in towing milage though. The trailer I towed was a tounge pull 29' 6200# camper. I'm thinking of going with 4.10's just for performance reasons. I sold the trailer.

1BADZ71 · October 16, 2002

If you are 2wd with a close to stock tire size, I would definitely recommend going 4.10. I wouldn't waste time or money going with 3.73. I have a 2000 GMC Z71 and I put in 4.56 gears and an Eaton Locker and 285/75/R16 BFG A/T's. That's about the equivelant to your stock tires size and 4.10. Wow! what a difference. I pull a 21ft sport trailer with several bikes, 110gal of water, 30gal gas, propane, etc. After all is said and done, I'm at about 7500lbs. Dry trailer weight is 5200lbs. I can conquer any hill that comes my way. I pull it down into first gear and away I go. I have friends with F350's and Excursions with the Power Stoke Deisel and they can't keep up on the hills. I used the Hypertech programmer also to change the speedo for both tire/gear changes. The increase the programming gives you too will help also on some of the hills. Anyways, just an addition to what everyone else has said. Good Luck!!!!

gsp473 · October 17, 2002

Fast 4.8,

Yes towing package and locking diff. I appreciate all of the input. Thanks.

Also does anyone know the deal with this oversized air filter that is supposed to come with the towing package?

My Air intake tube has bulbous growths coming from everywhere. is that what I paid for. I have a friend with 99 Z71 and a straight tube. I don't know if this a 2000 design change or what.

Shaners · October 17, 2002

The growth on the intake tube is what I believe to be a resonator. The heavy duty air cleaner on the towing package is a mystery to me. I don't know if it is a high flow filter or if it has more pleats for better filtration. Mine is sitting in a box in the garage because I put a K&N drop-in in my truck....

RedHand · October 23, 2002

I am very curious about this as well. I know it's a truck, not a race car. I've heard this a MILLION times from the significant other, parents, my brother (who just bought a 2002 Ford F150 FX4... no wonder he says it's not a racecar!

), etc. I had stock 3.73's in my 1987 Monte Carlo SS and matched with the 700R tranny and the 355 it hauled donkey! Now I have the 98' Z71 Ext Cab 350 Vortec, I wanna know what the rear axle IS (think it's 3.42) and if it's not 3.73, I want to put the Auburn in. Any suggestions?