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I just took a look at a ‘94 Yukon 6.5TD and a noticed a pretty loud high-pitched whine coming from the rear end when I was driving down the freeway. I would imagine that means the rear end is on it way out. What do you guys think? The rig has 157k miles.

Having recently blown up, and I mean destroyed, the rear-end in my '94 Blazer, I expected the whine on the highway to disappear, but its still there, you have to get over about 70 to hear it, same as before. I also have a strange noise sometimes when downshifting, as long as I do it at or below 50 it doesn't happen, but the exhaust sounds pretty cool to drop her into 2nd on the off-ramp ;)

my '94 HD limited slip whines/groans at 70. I pulled the axle and looked at the bearings and seals and then got used to it. I blew a rear and when I would let off the pedal the engine drag started the whine that didn't end till it stopped. I blew that one 100 ft from my parking spot trying to limp it home.

This would only whine when I stepped on the gas. If I let off the gas it was quite as a church mouse. Thanks everyone for your feedback, I feel much better about it now.

Also, can somebody please explain why every single 6.5TD I have ever driven has that ever so slight miss at highway speed. Very strange.:)

Rear axle whine has 2 causes: Worn gears or bad bearings or worn gears from bad bearings. Really it is a little more complex. In your yukon or Blazer you should have a gm 10 bolt rear. All of the bearings in the 10 bolt have a hard time holding up to a 6.5 td. The only real way to know for sure is to dissassemble the axle. I would bet you will find a bad carrier bearing. If the differential has run for an extended time with a bad bearing it could have caused damage to the ring and pinion. Gear noises can be tricky. Propper set up of new gears USUALLY results in quiet operation. I have repaired one for sure that would never run quiet because the housing wasn't machined correctly. Usually a good gear tooth contact pattern and back lash between .007 and .010 should make for a quiet running differential, along with good bearings and propper preload. Gm 14 bolts can develop gear whine after lotssss of miles, but not real common. Again, check bearings and if necessary reset back lash.;)

i recently completed a swap of a 14 bolt semi floater to replace the 10 bolt that i broke the tubes loose in. i had the 10 bolt rebuilt a couple years ago and was already getting a bit much lash out of it. they should have never put a 10 bolt behind a diesel even in a 1/2 ton truck. everything that got the 6.5td also got the 4l80e tranny why not a decent rear? anyway a 99 gmc yielded me this 14 bolt 6 lug semi floater and it kicks ass. now i can launch it without worrying. it also has the gov lock wich seems to work much better than the gov lock in the 10 bolt. i guess size does matter.

Jauncho

If you only hear the noise when you step on the accelerator, I would be led to believe that you have bad Pinion Bearings.

I think carrier bearings would be more pronounced on coast.

How hard is it to swap in a 14 bolt semi-floater? Does it just bolt right on? Also, it seems like it would be a lot less work to just drop the entire rear end then to try and rebuild it in place.

it was easy. the only adaptor i had to use was to adapt my driveshaft to the rear yoke which required NEAPCO part# 2-1153. its just a u-joint with 2 different size journals and clip types. the 14 bolt was about 1/2" longer forward(which didn't matter to the slip yoke) and the 14 bolt is about 1" wider to the outside of the drums. my 15" wheels even fit over the drums. the parking brake cables worked with some adjustment. check out www.neapco.com and go to aftermarket and catalogs and find what you need. they don't sell direct but i got what i needed at carquest locally but i'm sure you could find it online. if your burb is 1/2 ton it will probably be the same as my blazer. at first i didn't like the big heavy drums but after driving it and towing with it i love 'em. let me know if i can help anymore, PM or just post!

big and beautiful

Ummm, is your pinion angle correct?

lupey,
Do you need a longer driveshaft for the big differential? you have decent alignment now, but the diff input yoke is reaching up to the driveshaft a bit . . :confused:

i couldn't help myself and i added 2" blocks to it while i had it apart. this particular rear had been in a project k5 for a short time (swapped back out for ground clearance) and the perches had been moved. so when i welded the new ones back where the origionals were i set the angle where it is now. the slipyoke is 1/2" farther into the tailshaft then it was with the 10 bolt. the angle should be more parallel to the output of the transfer but i got some bad info on setting the angle and i was more worried about having the angle more equal to the driveshaft( like a cv setup ) rather than the output. the driveshaft would be plenty long enough even without the reach up. theres no vibration so i'm happy with it anyway.