I just bought an 03 1T. HO 6sp 4.10. I test drove it to check for noises but didn't drive far enough. After driving it 35 mi. home (warming it up good) was a different story. It ground badly going into reverse when I backed into the garage - the reverse synchro doesn't work good and 3rd, 4th and 6th gears are noisy, when warmed up. Today I pulled the diff cover and it was low about 1 1/2". I know the stories about being shipped low on lube but this lube looked and smelled good - I doubt it has 25k miles like the rest of the truck. I put my dial indicator on the carrier and it has about .001" slop, rather than having some preload. The pinion also feels like it is down to nearly zero rolling tq.. Time for some warranty work already! I called the dealer shop and they are very defensive, before even checking it out. They claim a mech. completely checked it out before it went on their lot. I think I'm in for a hard time with them. Does anybody have a shop manual with the backlash, the pinion rolling tq. and combined, pinion and carrier rolling tq. values? At least the gears look very good. The carrier has an odd shape (not round) and doesn't have normal spider gears in there. I see helical cut gears but not beveled and they aren't in the center like spider gears. What kind of diff.is it?? I need to study the owners manual for clues. Any help is greatly appreciated - TIA! Craig

 

the diff is similar to the Torsen diff used in the H1 Hummers. The fluid should not have beenmore than 1/2" down from the fill plug. obviously they DID NOT check the rearend and I bet any of the others!

 

DC requires the diff serviced every 15k miles. Standard fill is 75w-90 synthetic. If towing heavy or live in the deep south 75w-140 synthetic is recommended.
For the tranny Pennzoil Synchromesh fluid is DC approved, but Redline MTL and Amsoil MTF will also work in the NV5600 and is synthetic unlike Pennzoil.

MikeyB

 

Craig I don't have the manual but as per your quest - what is it - it's an AAM 11.5"

http://www.aam.com/technology/tech_p..._rearaxle.html

 

My rear diff went south at 12K. Funny thing was that the noise seemed to come from the transmission especially in fourth gear. What clued me into the diff problem was that I didn't like the wear pattern on the ring gear. The dealer said normal and the noise got louder until they replaced the gears. The "transmission" noise was gone with the new gears. Obviously the whine telegraphed up the driveline into the transmission. Now, this has absolutely nothing to do with the synchros but might explain some of the noise. Since I tow heavy I switched to Redline 75W140 with the new gears and so far she is still nice and quiet.

Casey

 

For the 11.5 AAM, backlash (from the text) should be .003-.010 in with a preferred backlash of .005-.007 in. Should not vary more than .002 in between measuring points.

I didn't see anything about rolling torque, but (hth):
Pinion bearing preload torque:
New bearings: 15-25 in lbs
Original bearings: 10-20 in lbs
Pinion bearing preload + Diff case bearing preload - New bearing 30-50 in lbs
Pinion bearing preload + Diff case bearing preload - Orig bearing 30-50 in lbs

If its under warranty and making sounds I would take try and take the service manager for a back to back ride in a new truck (with silent gears) and yours - for comparison. They are NOT supposed to make sounds - they're supposed to be silent. They're trying to avoid paying out warranty work without DC approval (in case DC doesn't concur with the diagnosis). Get DC involved.

An inch and a half low is excessive - then again, mine was that low when it was brand new too. It had 3687 miles on it when I checked.

I'm now running 75W-90 up front and 80W-140 in the back. I've got 47k on the truck and have changed it out twice (tranny and xfer case too).

You said the truck has 25k miles and the synchro's are also bad? Something doesn't sound right here.....

Keep on them, and get it fixed. You'll love driving that truck.

 

Thanks a bunch, guys - that answers everything! 5th gear is the only quiet gear - I figured because it's direct. 3rd and 4th are the worst and 6th is a little noisy. The noises are the worst at low speeds and low loads. The pinion teeth are smooth and shiny and the face wear is even but it could still be causing noises. That preload tq. table is exactly what I needed. I put brgs. in my 80 at 48K and that's exactly how Dana told me to set it up, 20 - 25 for the pinion tq. (a.k.a. rolling tq.) and no more that double the pinion tq., for the total tq. Then I went to 80w140 in the 80 and that was the best thing I did - even when I lived in Co.. I always got a lot of black smudge on the magnet with any other weight lubes. The NV5600 rear seal is leaking a little and it was about 1/4" low. I don't think the fill plug was ever taken out - I had to dig dirt out of the hex pocket to get the Allen in. The diff plug is badly burred so I know it's been looked at, but left low. The 03 was a fleet truck and the oem 7-70 warranty wasn't transferable so I bought a 2-30 warranty. I also have the dealers' 30 day (or 30 feet) warranty. I'm going to ask them to do the work under the 2-30 DC warranty and they pay the $100 deductable for me. Thanks again! Craig