TSB for front differential problems

[baldridp]

After two months of beating my head against the desk trying to track down a strange sound, I have finally found the answer. Two months ago I lifted my truck with the Superlift knuckle kit. Coincidentally at the same time I developed a sound from the front end. The sound was a shoop shoop sound. Kinda like tire balancing, but I swapped tires and the same thing. I had alignment rechecked. All was good in that area. I had both front and rear diffs serviced and no problems there. I had driveshaft (rear) checked for proper angles and balance. It to was found to be good. Ahhhhhhh. So I finally went to the dealer! (star wars darth vader music playing in the background). Tech drove truck with me and we agreed a noise did exist, however they said " with the lift greater strain is placed on the bearing on the axle flange and wheel hub and that is what you are experiencing. I said no, the lift with the new knuckle keeps all factory alignment points and geometry within specs. I suggested he check the TSB list. Guess what!!!!!!!!!!! There is a new bulletin out for the front differential. It says to the effect:

Some customers may experience a sound at 30 mph similar to a roar or vibration that comes and goes increasing with vehicle speed up to 45mph. This sound will exist only in 2 WD. When auto 4WD or 4 WD high are engaged the sound goes away. This is due to a flaw in the differential housing where the axle/ axle flange inserts are. This hole or opening becomes elongated and cause slop or play in axle flange. This is a warranty fix. Evidently with front driveshaft enaged, the front end is "loaded" up and rigid and doesn't diplay this slop. We road tested this to confim and this was my problem to the T. I'm just happy I don't have to pay for this fix. I remained calm and pleasant with the dealer and reached a professional resolve. It also helps this dealer sells trucks with larger tires and wheels and installs lowering/lifting components.

 

[nfhjr]

Thanks for the info, if you could please give the TBS number in another post as i seem to have something close to what you are having

 

[decklift]

I would like to know TSB for front differential problems.
Thanks
David
2002 NFE
front brearings out

 

[baldridp]

Well I got the front differential case replaced last week. However the vibration I had at 35 is now occurring at 52. Agggh! I have another appointment on Wednesday to get it looked at AGAIN. I'm also getting the right hand mirror replaced because the defrost function quit working in it. Strangely on my repair invoice the dealer ordered a differential case and replaced all of the guts from the old and put into the new, but they only replaced the right half of the case. This puzzle me since I still have slop in my left hand axle shaft as it comes out of the diff housing. I will reengage on that issue. I may even pursue getting them to order a complete front diff assembly. My picture shows the left half of the diff case that the lift installer ground off the upper diff mount for clearance. This should have been replaced by the delaer when they got the new case. The yellow arrow shows the vertical play I have in the axle shaft. If I grab the CV shaft and pull up and down on it I get deflection. I don't experience this on the right side nor on other Chevy trucks that have this same front diff (Suburban, Tahoe and Silverado P/Us). Anyone else have this play?

 

[Chief]

Gads - the General would be well serviced to offer a better front differential in their vehicles. I know the 2002 models had recall issues and the front differential is pretty weak, especially when compared to the beast in the rear axle.

 

[baldridp]

Well! After many days without my truck (26 total between 3 dealer visits) I finally have my truck fixed! The first visit the dealer checked, balanced and inspected everything. This was to be expected. They referenced a TSB for a diffential issue that was related to a manfacturing defect/flaw. They replaced the front diff case. This "case" is not the exterior case that I once thought. It is actually the housing that the ring gear mounts to inside of the diff. Strange nomenclature. However this did not fix my problem. I drove it for another few weeks till I could take it back to the dealer. Without question the dealer took the truck in for service and had a GM regional tech come out and inspect the truck. They did a vibration analysis with the computer to look for certain frequency signatures. They reinspected all parts and retorqued everything. My problem was still there however. I decided to take the truck to a driveline specialist. They examined all aspects of the truck to include wheel balance, driveshaft balance, driveshaft angles and all areas were determined to be in proper order. However they did say without opening the inside of the front or rear diffs that they were limiting their dianosis. I returned to the dealer again and I had been driving the truck in 4WD High and had experienced a whining sound with it engaged. They finally clued in that the bearings might be bad and be causing the ring gear and pinion to wear funny. They took the truck and 4 days later called and said it was fixed. I had my suspicions. Guess what! They finally fixed it! The left outer axle bearing was bad as was the two bearings that support the diff case that they replaced on the first visit. My dealer experience was very positive through the whole thing. Never did they say "sorry its lifted we can't touch it" like 2 other dealers said (Ken Dixon/Ourisman). They always gave me a loaner car free of charge and treated me decently. All work was done warranty! Here is the kicker...I didn't even buy the truck from them! But I will buy my next truck from them though! Jack Winegardner Chevrolet in Fort Washington Maryland is one great dealer to work with.

 

[WCFields]

I like good dective work and love happy endings!

Glad you hung in there and worked with them instead of the other way around!