gmc truck noise want help

[bmun]

whenslowing down to stop butnot stopping all the way when you excelerate you hear a clunk like the rear end or the tranny any ideas.

[Kennyray]

Lube the inside of the yolk on your drive shaft and see if the noise goes awayI believe there was a TSB about that

[bmun]

i had to put a tranny in about a month ago and it has done it ever since but i bought the truck with the tranny bad so i dont know if it was pre exsisting or not

[Kennyray]

just lube it up and see what happens . won't cost ya nothing but time and a little bit of grease.

[bmun]

i appreciate the help hope i can help you sometime

[Kennyray]

post back with your your results and stick around, this is a very user friendly site and if you have snooped around we have cookies, just have to provide your own beverage.

[chengny]

Many people report a noticable noise that occurs in the situation you describe (and I believe Kennyray's solution is the no. 1 remedy) However, there is another cause that eminates from that area. The splined interface between the driveshafts and the transmission/transfer case. It is generally the rear drive shaft.

When you come to an abrupt stop, the front brakes (as designed) do most of the stopping and the front of the truck slows much faster than the rear. The rear end eventually catches up and slows to the same speed. But what happens during that period of time is that the entire driveline compresses, due to the different rates of deceleration. When you accelerate again the drive train relaxes and streches back out. That is one of the reasons the drive shaft is splined.

If the splines are dry, as they return to there streched out length, they will make a groan or squeak. This is the faces of the splines as they slide along each other. There is usually a grease fitting ( or a tapped hole to accept one) in the splined area.

But like I said, it sounds like KR's answer is most likely what you will find. Grease the splines anyway.

[gmctrucks]

Originally Posted by Kennyray

Lube the inside of the yolk on your drive shaft and see if the noise goes awayI believe there was a TSB about that

Kenny is 100% right I thought when my truck was new that somebody rear-ended me once the dealer lubed it no more problems.

[BernieB]

Originally Posted by chengny

Many people report a noticable noise that occurs in the situation you describe (and I believe Kennyray's solution is the no. 1 remedy) However, there is another cause that eminates from that area. The splined interface between the driveshafts and the transmission/transfer case. It is generally the rear drive shaft.

When you come to an abrupt stop, the front brakes (as designed) do most of the stopping and the front of the truck slows much faster than the rear. The rear end eventually catches up and slows to the same speed. But what happens during that period of time is that the entire driveline compresses, due to the different rates of deceleration. When you accelerate again the drive train relaxes and streches back out. That is one of the reasons the drive shaft is splined.

If the splines are dry, as they return to there streched out length, they will make a groan or squeak. This is the faces of the splines as they slide along each other. There is usually a grease fitting ( or a tapped hole to accept one) in the splined area.

But like I said, it sounds like KR's answer is most likely what you will find. Grease the splines anyway.

Umm... Assuming this theory is correct, I just want to point out that accelerating in a rear wheel drive vehicle would also "compress" the drivetrain since the force is being applied from the rear.

Frankly, while your theory does have a certain logic to it, the main reason for the splined joint is to allow movement between the differential and the transmission, as the transmission & engine move on their mounts, and as the differential rises and falls (increasing and decreasing the angle to the transmission, and thus the length of the line) with the suspension, as well as the effects of "spring wrap" under hard acceleration and braking.

[chengny]

“That is one of the reasons the drive shaft is splined.”



Yeah, I agree - it is counter intuitive. But it is true - a vehicle's driveline actually elongates during acceleration after a stop (even with rear wheel drive). And at some point I knew why.


It’ll come back to me. Here is Popular Mechanics on the issue:

Many RWD cars and trucks exhibit a clunk when accelerating from a dead stop. It’s caused by friction in the splines that couple the transmission tailshaft to the driveshaft front yoke. Friction keeps the splines from sliding as the axle moves fore and aft slightly when transitioning from stopped to under way. When the truck starts moving, it all sorts out with a clunk as the splines slide longitudinally.

I think that may be happening here. The fix, or at least the diagnosis for clunking splines is to remove the driveshaft, and lubricate the splines with Motorcraft PTFE lubricant (Ford p/n D2AZ-19590-A).