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

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

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 .

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

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

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

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

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.

See http://superchevy.com/technical/engines_drivetrain/driveshaft_rearend/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

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.

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.

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.

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?

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.

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.

The best way to check backlash/pinion depth is to mark the ring gear with paint that comes with a new pinion/ring gear set. If your pinion is riding too close to the heel(too far out) you'll be able to see it in the mating mark. It is possible you switched the shims around using a thinner shim on the drivers side of the diff. Having to tap the shims in is normal..

Can't guess with tooth contact and backlash, the difference between .005-.007 preferred, to .015 is hard to tell by hand, you really need an indicator set up to check this, also there is special marking oaste used to check tooth contact, do drive and coast side.

Well all went well with install. Used marking paint as suggested and gears believe it or not aligned pretty well. Not perfect, but good enough according to some of the example pictures I found online. Anyway this was all for not as the pinion bearings are bad and will need to be replaced. The rear end is much tighter and quieter but still have noise during acceleration. So I guess I am going to tear it down one more time just for practice. :}

May leave it to a professional to do this time. It has been a great experience, and I appreciate all the feedback.

You have to get a dial indicator to check the backlash. The pinion does have a crush sleeve but since you didn't remove the pinion and the pinion bearings are OK then that part should be alright. Once you have the ring gear "in" and the bearing caps torqued you use a magnetic base indicator to check the backlash. The backlash is adjusted by moving/replacing shims from one side to the other. The pinion hasn't moved so you only have to make sure the ring gear is not too far from the pinion gear (too much backlash). You'll get a clucking sound if you have too much backlash just like you did when the bearings were bad. It's not really that hard to do if you know what and how to do it. The backlash checks for the "total" amount of clearance between the pinion and the ring gear. I don't remember the backlash spec but it's probably around .002-.005 in. The dealer or a mechanic can tell you exactly how much you need.

Treblig in Tx

backlash is 005-007, good advice on the issue, treblig69! Measure at 120 degree intervals, use the lowest setting another words, not under .005. at any point.

Thanks MAXWEDGE! My only fear is that brehmster didn't check the pinion bearings for wear. With bad ring gear bearings he will certainly have some some trash (metal particles) in the pinion bearings (we all know what that does) so it may just be a matter of time. I always go ahead and replace the pinion seal when I tear down the rearend especially if it has over 80,000 miles or so. Pinion seals always end up leaking sooner or later.

curious to see exactly how the contact pattern was. and did you load up the diff pretty good when you checked it?

Hey guys,

Well don't say u told me so! Pinion Bearings, as maxwedge/Treblig69 virtually predicted, are bad! Noisy on accel

@ this point I have in my hand new pinion bearings, crush washer, and seal.

What would be the correct way to go about this since I did not originally document my diff. removal. Should I just remove everything and reinstall with current pinion shim setup and then use the paint method to check for proper wear??? Would it be best to go ahead and measure for backlash before disassembly and again at reassembly or does it really matter @ this point to measure anything?

well new bearings are going to probably make the backlash tighter. all you can do is measure it now and when it goes back together and check the pattern. make sure you use a prybar and load that case up so you get a good pattern.

I doesn't matter. Once you take out the pinion it's like starting brand new except for being able to determine you new setting based on the old setting. In other words you could have used the old gear shim setting to calculate your new shim setting but since you had/have so much wear it probably will be just as easy to start from the beginning. They say if you have the new pinion crush sleeve pre-crushed it's alot easier. Any machine shop can do it. When you install the new crush sleeve you will have to basically crush it using a long breaker bar when you install the pinion nut unless you have a good sized air-tool. In order to overcome the initial crush sleeve stiffness it takes temendous torque and that's why it's best to get it pre-crushed. It won't cost very much but you won't have to kill yourself during installation. Once the crush sleeve is pre-crushed it makes it much easier to for you to torque the nut to the required torque/setting. The pinion doesn't really take shims or adjustment it takes pre-load. Once it is properly pre-loaded it won't ever move again. All the gear mesh adjustments are made using the ring gear shims (left and right). I believe the pinion has numbers on it that help you get the correct pinion depth. Either way the majority of the gear mesh adjustment is made using the ring gear bearing shims. It's kinda hard to go into all the detail on this site, besides I'm sure somebody has a web site for you to get all the details. Make sure you wash-out the inside real good after you remove everything. It doesn't take much to destroy new bearings. Keep your old shims as a reference. Make sure you lock the pinion so that it can't move at all as you set the backlash. If the pinion moves (and you don't notice), your setting will be wrong. Using a magnetic base dial indicator you simply stick the magnetic base to the rear end and make sure the indicator shaft is perpendicular to the gear tooth face. If the shaft is not perpendicular to the gear tooth the reading will not be accurate. With the indicator in place and the pinion locked-down you simply rotate the ring gear back and forth to see how far the indicator moves between touching the pinion teeth in one direction and the other direction. Actually it's easier to move the ring gear all the way in one direction then "zero" the indicator and then move the ring gear as far as it go in the other direction. This way you can read the movement more accurately.
I don't know how many characters are allowed on each response so I'm gonna stop for now. Does anyone have a web site with all the directions?

Treblig inTX

one more thing...Make sure you wash the new ring gear bearing as they will have collected some metal particles from the bad pinion bearings. Wash everything including the spider gears. Get as much dirt and metal out as possible. You will also find metal laying in the bottom of the pinion housing area, it might be hard to get but it's gotta come out. There will also be some trash in the axle housings but it usually says put (the cleaner the better).

Treblig in Tx.

Thanks for the info again Treblig69.

That really cleared it up in my mind. Makes alot more sense now. I have found a few good web sites for this and here is one for anyone else needing good info and some different tips on rear end work:

http://www.2quicknovas.com/happyrearends.html

So from here I will make sure and clean everything again really well and will see about getting the crush washer precrushed...and you say they can set the 25in/lbs before hand for you? Either way your just saying it is easier to have it pre-crushed.

Then once pinion is installed just make adjustments with the left and right differential shims as needed for back lash adjustments. Well, sounds easy enough. Thanks a bunch guys and will post back again soon.

Brehmster

Well I finally got a free Saturday to work on the rear end. Put new pinion bearings in and it all went well until I looked on the ground and seen my new pinion seal laying there. I think they recomend that you put this on first, so to anyone else go slow and dont forget the SEAL!!. Lucky for me I had an extra crush sleeve and was able to start that process over again. Also when I was putting my new bearing races in I was able to use the old race to pound the small one in, this one was easy. The big one gave me some trouble cause u can't get a hammer in the housing, so I thought about using my air chisel with a dull flat bit. It went in very easy with no damage to the race, just work your way around the race little by little and it goes in super easy with very little effort. Anyway it all went together very nice and is working great for me at the moment.


One thing I can recomend to anyone else with a noisy rear end and thinking about just changing certain bearings is to just do them all at the same time. Its a little extra work, but you will be so glad you did. I have torn down my rear end twice because I thought that my pinion bearings were good(they were not), and if I would have done them all at once (like some suggested)I would have saved myself a Saturday. So again thanks to all for there suggestions and help!

Brehmster