# 97 Tahoe 3.42 Gears And 5.7 Vortec



## Guest (Aug 6, 2005)

It seems that a lot of the posts have either 3.73 or 4.10 gears.
I checked my codes and my Tahoe has
3.42 gears.....
What does that mean??
Another code in my glove box is
Z82 and that is for Trailering Package SPL.
Another code is for Engine Oil Cooler
and I do see what I believe is a transmission cooler mounted on the front of the radiator (maybe 12"x 6"
in size)
Would it better to have 3.73 gears and how would that benefit ??
Would it be too costly to change the gears?? 
Bob & Judy (2blackdogs)


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## Katrina (Dec 16, 2004)

generally speaking, lower gears(numerically higher) will have a higher towing capacity.
A tahoe with 3.42 gears will not be ideal in my mind for anything bigger than a 21RS. You can check the owners manual for tow ratings though.

Changing gears will cost about 1000 dollars per axle. A 4 wheel drive means both axles must be done.

California Jim is the only Outbacker I know thats done a gear change, perhaps he can chime in.

As an example of how gears affect tow rating:
I just traded for a new truck that only comes with 4.10's when equipped with the 6.0 motor.
My old truck however had a 5.7 just like yours. going from 3.73 gears to 4.10 gears on it increased the tow rating by two thousand pounds.

on edit: I see now that you have a 25RS. Install a tranny temperature gauge, stay out of overdrive, and ignore the lousy gas mileage when towing.
I'll bet that thing works hard from a dead stop to get moving.


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## z-family (Oct 2, 2004)




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## David (Apr 23, 2005)

The gear ratio represents the number of rpm's the driveshaft turns in order to acheive one turn of the drive wheel. For example, 3.73 means the driveshaft turns 3.73 revolutions in order to turn the drive wheel one turn.


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## aplvlykat (Jan 25, 2004)

I know it's not quite the same truck but I did the gear change on my 2003 Tahoe. With the 3:42 gears, non-posi and the 4.8 vortec V8 it did Ok pulling my 25rss but would die on any hill. I would have to take hills in 2nd gear. Also the 3:42 gears are considered highway gears and have a tow rating was aprox. 6800 lbs., if it had the 3:73 gears the tow rating jumps to aprox. 7500 lbs and 4:10 gears it jumps again to 8200 lbs. You can see that there is a big difference. Like I said, I did change the gears and went with a Eaton 4:10 posi unit, same as Cal. Jim did. What a big difference in towing and pulling hills another plus was I got better gas mileage when towing, not much but a little. This is the biggest bang for the buck mod you can do. I found a off road shop that specailized in rear gears and had it done for $1000.00 with a one year warrentty. If you only want to upgrade the gears and not have the posi unit the price was around $650.00. I am sure you have a off road shop in your area and highly recommend the Eaton unit, if you can afford to do this it is money well spent. Kirk


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## fixjet (Jan 19, 2004)

that's the same setup I had in my 99 Suburban. It will do ok on the flats but hills will kill you. Also the higher gears will run hotter and put much more stress on the transmission, which is the weak link in the 1/2 trucks. My 01 suburban with 4.10's is not comparison. Goes up the hills with ease.


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## slivengo (Apr 13, 2004)

I have the same TV as you. The 3:42 gears did OK towing the Hybrid we owned but I knew it would be a problem with the Outback 26r. GM only offers the 3.73 for that model and I decided to put in the 4.10. Makes a world of differance. My gas milage has stayed the same while towing. My Tahoe is used only for towing. If I drove it every day I would probibly went with the 3:73's. We live in the Carolina's so we are camping in the mountains quit a bit. That is where you will notice the perfromance. 
Here is my problem and you may have the same setup. On my Tahoe the overdrive and drive is the same and I have no "overdrive lockout button" so I am driving in overdrive all the time unless I pull it down into 3rd which I do when I am pulling large hills and in the mountains. I wish I could lock it into drive but have no way of doing it. The other thing, is the susspension on the Tahoe is soft. I installed the "air-ride" air bags to the rear and it has helped a lot. I hope to get 2 more yrs of towing and then I plan on selling and going to something else.


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## kjdj (Sep 14, 2004)

Great info. I think I will ask for a new eaton 4.10 gearset for Christmas!

Aplvlykat,
Did the offroad shop re-burn the computer for the gear change? ie speedometer calibration?


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## camping479 (Aug 27, 2003)

Don't tell tdvffjohn 'cause he told me not to but I had our 3.42 changed to a 3.73, made a huge difference in pulling hills. Still not the best, but much better. The torque converter stays locked up much more than before. We plan on keeping the truck for 2 or 3 more years so I felt it was a money well spent.

My mechanic did it and took it to the dealer to have the computer reprogrammed. They got halfway thru the re program and the computer crashed and was rendered useless. They got on the phone with GM tech support and were able to get it replaced under warranty even though it's 5 years old and has 62k miles on it. I was pretty happy about that. Not sure if it was on the way out or what but now we've got a new one.

I agree with Kirk, the most bang for the buck as far as improving performance.

Mike


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## tdvffjohn (Mar 10, 2005)

Glad to learn I was wrong Mike.


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## camping479 (Aug 27, 2003)

You weren't wrong John, you just gave me your opinion based on your knowledge. I value your opinion and you made me think long and hard about it.

Mike


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## California Jim (Dec 11, 2003)

Good replies all, nothing really to add to the techie stuff. My only comment would be if you're happy with your current performance then don't worry about it. If you're lacking then a gear change would give you a good boost in towing power. Especially if you went to 4.10's


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## aplvlykat (Jan 25, 2004)

KjDj, I forgot to mention that part, what an ordeal. I will make it short. No, the off road shop did not do that type of work and the dealer refused because the 2WD 2003 Tahoe with 4.8 V8 does not come stock with 4:10 gears the 5.3 V8 does. The dearler told me to go buy an aftermarket tuner and reset the speedometer myself. They also told me that using a tuner, in my case it was the superchip, will not affect warrenty and they put it in writing on the invioce. This set me back another 400.00 dollars but did work as far as resetting the speedometer. This may have been only my local Chevy Dealer, Rancho Motors, but if you have a newer Chevy check with them as far as restting everything. Kirk


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