Cold Transmission Clunk

USMCPayne · January 5, 2009

So, I've noticed when the transmission is cold and I've driven for less than 10 minutes, if I come to a stop sign or stop light the truck almost seems as if it doesnt down shift from 2nd gear to 1st gear for a few extra seconds. When it does finally downshift there's a clunk sound and the truck lurches forward slightly, almost as if I've been "love tapped" from behind.

I took the truck to the dealership and described what was happening, and after looking the truck over and replicating the issue they took the driveshaft out, greased the splines between the shaft and the transmission because they were bone dry. They say this fixed the issue. I dont know yet because the truck is having some body work done while it was in the shop (killing two birds with one stone). So I'll have to wait and see when I get it back later this week.

Anyone have any knowledge of this? Drivetrain issues are not my specialty so anything anyone has to say would be appreciated.

anonemouse · January 5, 2009

So, I've noticed when the transmission is cold and I've driven for less than 10 minutes, if I come to a stop sign or stop light the truck almost seems as if it doesnt down shift from 2nd gear to 1st gear for a few extra seconds. When it does finally downshift there's a clunk sound and the truck lurches forward slightly, almost as if I've been "love tapped" from behind.

I took the truck to the dealership and described what was happening, and after looking the truck over and replicating the issue they took the driveshaft out, greased the splines between the shaft and the transmission because they were bone dry. They say this fixed the issue. I dont know yet because the truck is having some body work done while it was in the shop (killing two birds with one stone). So I'll have to wait and see when I get it back later this week.

Anyone have any knowledge of this? Drivetrain issues are not my specialty so anything anyone has to say would be appreciated.

My '02 Sierra had the same issue. Took awhile to figure it out, but mine went away after properly greasing the splines. I've heard that it's a common problem. Not a big deal to do yourself in the future. You should be fine now.

dkjbama · January 5, 2009

My new truck has this same issue and I have concluded that it is most likely just in need of grease on the driveshaft splines. I had a '98 GMT400 that had the same issue. Mine sat on the lot 7 months before I bought it so I'm really not surprised. GM does spec a special grease for this that costs close to $40 a tube, so I think I'll just let the stealership handle it when I get the chance.

bigdogxx · January 8, 2009

My new truck has this same issue and I have concluded that it is most likely just in need of grease on the driveshaft splines. I had a '98 GMT400 that had the same issue. Mine sat on the lot 7 months before I bought it so I'm really not surprised. GM does spec a special grease for this that costs close to $40 a tube, so I think I'll just let the stealership handle it when I get the chance.

Hopefully your dealer does not stick it's hand out like mine did and request 100 bucks to grease it, and yes my truck is still well under warranty. They refer to this problem as a common maintenance item which is absolutely bs!

Shadow_Warz · February 18, 2009

I've got the about the same problem except it only "clunks" coming out of 1st into second. And how easy/hard is it to grease your splines? I'm not afraid to get my hands dirty but I kinda want to know what I'm getting into before I start tearing apart my truck. Thanx

jbstx · February 18, 2009

previous post linkhttp://www.gm-trucks.com/forums/index.php?...207&hl=yoke

Check out this link. It has some good info/experiences with the same issue.

http://www.gm-trucks.com/forums/index.php?showtopic=85207&hl=yoke

DanJS10 · February 18, 2009

I recently had this same problem with my 2008 Sierra. I took it to the dealership and they sent their driveline tech on a ride along with me so he could hear the problem. He said it was the slip yoke in the transmission that needed to be greased. He also said that when you hit the brakes the leaf springs, being so soft, let the axle rotate rotate slightly downward, causing the slip yoke to slide out of the transmission a little bit which is completely normal. When the yoke is dry, there is a loud clunk as it forces itself back into the transmission.

When we got back he said he would take the driveshaft out and grease the slip yoke and it would take about 30 min. Well, after the yoke was regreased the problem is completely gone.

DanJS10 · February 18, 2009

I've got the about the same problem except it only "clunks" coming out of 1st into second. And how easy/hard is it to grease your splines? I'm not afraid to get my hands dirty but I kinda want to know what I'm getting into before I start tearing apart my truck. Thanx

It's not too difficult but you have to make sure that you put the driveshaft back the exact same way you took it off. The driveline tech told me that if you install the U-joint 180' around, it could cause a driveline vibration. The driveshaft's are balanced with the slip yoke and u-joint already installed and any weight that is added during the balancing process could be improperly positioned if the driveshaft is reinstalled incorrectly.