A Clunk But More Like A Clank!

fighter42487 · October 7, 2009

when truck shifts to 2nd gear i hear a clank under the truck, could it be my yoke? or transfter case

txab · October 7, 2009

Have you made a visual inspection of the drive line components yet?

fighter42487 · October 7, 2009

Have you made a visual inspection of the drive line components yet?

no not yet, i took it up to dealer and he said it was normal, but my buddy has a truck just like mine and his doesnt make the sound. its not constant but more often than not.

Spurshot · October 7, 2009

Take 10 minutes and pull the driveshaft and lube the internal splines of the yoke with a good synthetic grease like Mobil 1 or your best choice.

dlstewart01 · October 7, 2009

Might want to use something a little better than Mobil 1. GM recommends a high temp grease that won't run. I have a small can of the grease from GM it is special lubricant high temp ptfe filled non melting grease part# 12345879, but.... that sh!ts 40 dollars and that was wholesale.

A lot people go to a boat shop and get a good high temp water proof marine grease. They say it works well. Greasing the splines on the yoke is fairly easy, you just have to take the drive shaft loose.

And the Dealer is full of it.

sab316 · October 7, 2009

Having this same problem. Took it to the dealer and told them I think its the yoke. They are trying to tell me its something else (circle ring, slip ring... something along those lines thats loose). They also tried to re-learn the transmission and flushed the valves.

I'm taking it to another dealer sometime this week and telling them its the yoke and hopefully they'll go that route instead. This other dealer didn't even try to pursue that option. Hopefully I can get this fixed cause feeling like I'm getting rear-ended every time I stop is annoying.

Spurshot · October 7, 2009

I've been wondering if this could be cured by stopping axle wrap-up.

Spurshot · October 7, 2009

Don,

Your comment got me curious, since I use Mobil 1 chassis grease on a lot of things from my 2500 to my shotgun hinges. The website says the operating range upper limit is just over 300F and the dropping point is 550F. It is recommended for disk brake wheel bearings on their site. I had read this material yrs ago when I started using it but had forgotten about it. But, I agree that a teflon or possibly a moly lube could be better for this. I'm wondering if the moly lube might contaminate the fluid though.

http://www.mobil.com/USA-English/Lubes/PDS...etic_Grease.asp

dlstewart01 · October 7, 2009

Don,
Your comment got me curious, since I use Mobil 1 chassis grease on a lot of things from my 2500 to my shotgun hinges. The website says the operating range upper limit is just over 300F and the dropping point is 550F. It is recommended for disk brake wheel bearings on their site. I had read this material yrs ago when I started using it but had forgotten about it. But, I agree that a teflon or possibly a moly lube could be better for this. I'm wondering if the moly lube might contaminate the fluid though.

http://www.mobil.com/USA-English/Lubes/PDS...etic_Grease.asp

I don't know see this thread.

http://www.gmfullsize.com/forum/showthread.php?t=146143

I have mobil 1 in my grease gun right now. It is not that thick and will separate some what. I have a few tubes of castrol high temp synthetic red that is much thicker than the mobil. I have had a tube of Red Line synthetic that was good.

That grease that GM recommends and sells is Verrrrrry good. But it is expensive.

I have not used the marine grease but I have been told it works very well.

http://www.summitracing.com/search/Departm...GM-Performance/

http://www.castrol.com/castrol/sectiongene...ntentId=7022329

http://www.hrpworld.com/index.cfm?form_pro...;action=product

fighter42487 · October 7, 2009

Take 10 minutes and pull the driveshaft and lube the internal splines of the yoke with a good synthetic grease like Mobil 1 or your best choice.

im gonna try this sometime this week and let you all know how it works for me. thanks again, at least you guys gave me some kind of answer, its like the dealer just doesnt want to bother

Spurshot · October 7, 2009

I've seen a very thick moly marine grade grease somewhere in the past. I'm still thinking the axle wrap-up from braking and accel, if limited, could be helpful.

fighter42487 · October 7, 2009

I've seen a very thick moly marine grade grease somewhere in the past. I'm still thinking the axle wrap-up from braking and accel, if limited, could be helpful.

im not to familiar with axel wrap up, can you explain or tell me how it can be fixed( welding is not a problem)

Spurshot · October 7, 2009

I've seen a very thick moly marine grade grease somewhere in the past. I'm still thinking the axle wrap-up from braking and accel, if limited, could be helpful.

im not to familiar with axel wrap up, can you explain or tell me how it can be fixed( welding is not a problem)

At the ring/pinion, the torque axis is changed 90 degrees. Upon acceleration, the torque of the axles (internal axle shafts) act against the tire contact with the ground. There is resistance to that torque because of tire cohesion to the road, weight of the truck, etc.. At the ring/pinion, the torque acts on the axle housing in the opposite direction of the tire rotation.

With a simple leaf spring suspension like our trucks have, there is only the leaf spring itself to hold the axle housing and to resist that torque trying to rotate the axle housing in the opposite direction of the axle shaft rotation. Leaf springs allow movement (rotation) on acceleration, which rotates the pinion/yoke up causing it to get slightly closer to the transmission/transfercase, due to the installed angle of the axle housing. This is the reason the front yoke of the driveshaft slides in on acceleration and the opposite torque on the axle housing occurs on braking causing it to rotate the pinion downward, pulling the front yoke out of the trans/transfercase.

The solutions for axle wrap-up were mainly designed as traction control devices to prevent wheel hop. They include clamp on (the leaf spring) traction bars, ladder bars, 2 link bars, 4 link bars, and probably some others I've forgotten. All are designed to prevent rotation of the axle housing while allowing up and down movement of the suspension.

Heres a link to some 4wd guys' thoughts on it. It's not bad.

http://www.4x4wire.com/jeep/tech/susp/axlewrap/

I'd like to know if the Suburbans/Tahoes with rear coil spring suspensions have the clunk?

dlewis1111 · October 7, 2009

Don,
Your comment got me curious, since I use Mobil 1 chassis grease on a lot of things from my 2500 to my shotgun hinges. The website says the operating range upper limit is just over 300F and the dropping point is 550F. It is recommended for disk brake wheel bearings on their site. I had read this material yrs ago when I started using it but had forgotten about it. But, I agree that a teflon or possibly a moly lube could be better for this. I'm wondering if the moly lube might contaminate the fluid though.

http://www.mobil.com/USA-English/Lubes/PDS...etic_Grease.asp

Mobil 1 is what is called for on the wheel bearings of the 22,000 pound helicopters that I fly......the landing gear takes a good beating and we have never had any bearing problems related to the type of grease that is used.