Rear End Bad--Gear Ratio Question?

brehmster · 01-07-2006, 09:46 AM

Hello,

I have a 97 tahoe 4-door 2 wheel drive. The rear end is shot. Apears to have been run with low fluid. I changed out fluid and it quieted down a bunch but not enough to drive it with confidence. Anyway I found a rear end for $300 but it is a 3.08 gear ratio (GU6) and mine calls for the 3.42 (GU6). Can I put the 3.08 in it without destroying my transmission. Does that throw off the computer???? I really do not do any pulling with my truck so I think if I am correct that gear ratio would improve my gas mileage a bit. I do not want to get it if it is going to cause me problems. Any help much appreciated, thanks.

Brehmster

95tahoe4x4 · 01-11-2006, 08:09 PM

2-wheel drive, go for it. If it were 4x4 you would need to change the front diff as well. You might need to go get the computer flashed for different shift points, the dealer can do that..

Kt

corning_d3 · 01-11-2006, 09:02 PM

The 3.42 is a lower gear ratio, so acceleration will be increased, and top speed decreased. It shouldn't drop your fuel economy by much, though. Something to go by: The ratio(3.42) is actually how many revolutions the driveshaft makes for every 1 revolution of the differential .

2000CAYukon · 01-11-2006, 09:25 PM

I think he already has 3.42s and is going to 3.08s. You will loose some torque off the line and it will increase your top end speed.

You will need to reprogram for the gear change; otherwise, speedo and shift points will be off.

//2000CAYukon

corning_d3 · 01-11-2006, 09:38 PM

Oh....duh. Thats what i get for speed-reading..

horse482 · 01-12-2006, 04:36 PM

Your speed-o-meter will not read correctly, you will have to have the ecu re-calibrated.

Treblig69 · 01-12-2006, 07:51 PM

Quote:

Originally Posted by brehmster

Hello,

I have a 97 tahoe 4-door 2 wheel drive. The rear end is shot. Apears to have been run with low fluid. I changed out fluid and it quieted down a bunch but not enough to drive it with confidence. Anyway I found a rear end for $300 but it is a 3.08 gear ratio (GU6) and mine calls for the 3.42 (GU6). Can I put the 3.08 in it without destroying my transmission. Does that throw off the computer???? I really do not do any pulling with my truck so I think if I am correct that gear ratio would improve my gas mileage a bit. I do not want to get it if it is going to cause me problems. Any help much appreciated, thanks.

Brehmster

I just replaced the 3.42s in my '99 Tahoe 2WD. I got some 33s (tires) and wanted my low end acceleration back. It now has a 4.10 ratio gears and the 3.42s are just laying there looking for a home. There at my friends house, you can have them for $30 if you pay the shipping. The other guys are correct about one thing...your speedo will be off if you change from the 3.42 ratio it can also mess with the ABS system. I had to buy the hypertech computer programmer ($295.00) to get the Tahoe computer, tires, speedo, gears and ABS to cooperate.

Treblig in Tex

brehmster · 01-12-2006, 09:51 PM

Quote:

Originally Posted by Treblig69

I just replaced the 3.42s in my '99 Tahoe 2WD. I got some 33s (tires) and wanted my low end acceleration back. It now has a 4.10 ratio gears and the 3.42s are just laying there looking for a home. There at my friends house, you can have them for $30 if you pay the shipping. The other guys are correct about one thing...your speedo will be off if you change from the 3.42 ratio it can also mess with the ABS system. I had to buy the hypertech computer programmer ($295.00) to get the Tahoe computer, tires, speedo, gears and ABS to cooperate.

Treblig in Tex

Well, I do appreciate the offer but I am in the middle of putting new bearing in the existing one. I am pretty sure the pinion bearings are good and that the inner and outer axle bearings are the ones that are making the noise. I thought I would just get a junk yard rear end and be done with it but after thinking about it I thought I could be buying anothe bad rear end or one that would not last. But you know I will keep you in mind as I have not got the differential out yet to check the pinion gear and bearings...so they could still be bad????

By the way do u need an axle puller to get the axles out? Having a hard time @ this point getting the axle to come out. I have the differential clamps out and the "retaining clips are ready to fall out but cannot get the axle to pull out.

How is your gas mileage with the 4:10 gears???

Thanks in advance for any help, Brehmster.

2000CAYukon · 01-12-2006, 10:14 PM

See http://superchevy.com/technical/engi...nd/0506sc_ten/

Once the pin is removed, push the axle towards the differential so that the c-clip is easier to remove.

Note that once the pin is removed, you should not rotate the axles.

//2000CAYukon

Treblig69 · 01-13-2006, 04:56 PM

Quote:

Originally Posted by brehmster

Well, I do appreciate the offer but I am in the middle of putting new bearing in the existing one. I am pretty sure the pinion bearings are good and that the inner and outer axle bearings are the ones that are making the noise. I thought I would just get a junk yard rear end and be done with it but after thinking about it I thought I could be buying anothe bad rear end or one that would not last. But you know I will keep you in mind as I have not got the differential out yet to check the pinion gear and bearings...so they could still be bad????

By the way do u need an axle puller to get the axles out? Having a hard time @ this point getting the axle to come out. I have the differential clamps out and the "retaining clips are ready to fall out but cannot get the axle to pull out.

How is your gas mileage with the 4:10 gears???

Thanks in advance for any help, Brehmster.

You said you had the differential clamps out. There are main bearing caps on each side of the ring gear assembly and there is a pin which resides right between the axle ends. The pin has a long set screw that holds the pin from falling out. After backing out the set screw and removing the pin you can move each axle "into" the center section which allows the C-clips (in the end of each axle) to be removed. Once the C-clips are removed the axles should come out without much force (by hand). The main bearing caps hold each carrier bearing on each side of the ring gear assembly. The C-clips keep the axles from falling out and the pin keeps the axles from moving in (that way the C-clips don't accidently fall out.
I haven't noticed any difference in gas mileage but there is a big difference in power. I would say my gas mileage stayed the same if I could just keep from having so much fun with the newfound power.

Treblig in Texas.

brehmster · 01-14-2006, 08:53 AM

Quote:

Originally Posted by Treblig69

You said you had the differential clamps out. There are main bearing caps on each side of the ring gear assembly and there is a pin which resides right between the axle ends. The pin has a long set screw that holds the pin from falling out. After backing out the set screw and removing the pin you can move each axle "into" the center section which allows the C-clips (in the end of each axle) to be removed. Once the C-clips are removed the axles should come out without much force (by hand). The main bearing caps hold each carrier bearing on each side of the ring gear assembly. The C-clips keep the axles from falling out and the pin keeps the axles from moving in (that way the C-clips don't accidently fall out.
I haven't noticed any difference in gas mileage but there is a big difference in power. I would say my gas mileage stayed the same if I could just keep from having so much fun with the newfound power.

Treblig in Texas.

Hey thanks all of you for the help, has been priceless. Started out a bit intimidating and now I can see there really is not that much to it. I still have it apart and am working on getting the bearing replaced @ this time and also trying to remove the axle bearings( a bit stubborn).

Thanks again, Brehmster.

maxwedge · 01-14-2006, 10:43 AM

Quote:

Originally Posted by brehmster

Hey thanks all of you for the help, has been priceless. Started out a bit intimidating and now I can see there really is not that much to it. I still have it apart and am working on getting the bearing replaced @ this time and also trying to remove the axle bearings( a bit stubborn).

Thanks again, Brehmster.

May be off base here, but if you had the pinion gear out you will need a new crush collar and an inch # torque wrench to set the pinion pre load. Also may want to check back lash when re-assembling, using a dial indicator of course.

brehmster · 01-14-2006, 02:06 PM

Quote:

Originally Posted by maxwedge

May be off base here, but if you had the pinion gear out you will need a new crush collar and an inch # torque wrench to set the pinion pre load. Also may want to check back lash when re-assembling, using a dial indicator of course.

I have gutted the entire rear end except for the pinion gear. I know this may not be what most would do but I really am not familiar with setting preload and backlash...so I left my pinion gear in as I have no play or wobble in it and also the gears themselves looked good. No uneven wear or anything like that. I am replacing all bearing otherwise as the unit was run low and I am pretty sure the outer wheel bearings are the noisy ones. But anyway, will I have problems with tolerences when putting the differential back in with new bearings and races even though the pinion gear has not been removed? I have read some on preload and backlash but am having trouble really understanding it completely so I have opted to try it this way and hope it turns out OK......Good idea or Bad?

maxwedge · 01-14-2006, 04:38 PM

You better turn the pinion gear by hand and see if you can feel a roughness in the bearings. Also you really should have checked the back lash before dis- assembly to makes sure the gears are restored to the original setting, it is possible the tooth contact and back lash could change with the bearing change but this normally would only be a small amount still within specs. But here in this case you really won't know. I assume you kept the lt/rt diff shims in order, this is your no. 1 priority for re-assembly.

brehmster · 01-16-2006, 12:54 PM

Maxwedge,

Ok I guess I jumped the gun a bit on my removal of the differential. I did however keep my left and right parts together for reassembly but unfortunately did not check the back lash before removal. I now have the new bearings installed on the differential and have put the differential back in. The shims on the differential fit tight this time had to tap them in to fully seat them. On removal they just fell out. I am going to check the wear marks on the ring gear next just to see how bad it really is off, if at all. I have a bit of play as I work the pinion yolk back and forth is this normal or is the pinion depth off??? Thanks again for your replies.

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