2003 gmc yukon clunk noise when putting in drive and switching to reverse

[Summajet]

I finally got the motor in and running. Yesterday I drove it out the garage and when putting into reverse it makes a loud clunk noise. When switching to drive it does the same thing. Truck has been sitting about 5 months on jack stands, yes 5 months..LOL

I had seen youtube videos of similar clunks, noises when shifting into drive and then reverse. They mentioned that the splines on the driveshaft that feed into the transfer case gets dry. One member mentioned using the AC Delco Synthetic grease for the splines of the drive shaft. Prior to sitting that long time, it had no noise.
It makes no clatter noises when driving at 30 mph. Going to drop off tonight for inspection tomorrow.
Any ideas?
Thanks

 

[iamdub]

I finally got the motor in and running. Yesterday I drove it out the garage and when putting into reverse it makes a loud clunk noise. When switching to drive it does the same thing. Truck has been sitting about 5 months on jack stands, yes 5 months..LOL

I had seen youtube videos of similar clunks, noises when shifting into drive and then reverse. They mentioned that the splines on the driveshaft that feed into the transfer case gets dry. One member mentioned using the AC Delco Synthetic grease for the splines of the drive shaft. Prior to sitting that long time, it had no noise.
It makes no clatter noises when driving at 30 mph. Going to drop off tonight for inspection tomorrow.
Any ideas?
Thanks

The splines being dry was gonna be my first suggestion. It's an easy fix. Wouldn't hurt to check out the U-joints while you/they are under there.

 

[OneofFew]

It could be a whole host of issues, most likely one that originates with something you touched given that the noise started after your work.
-idle too high
-transmission issues
-loose motor mounts
-u joints
-rear end slop

There is no getting around having someone listen and pinpoint the origin of the noise while it occurs.

 

[OR VietVet]

Check that trans mount as well. If I was going to deal with the splines I would mark the shafts and pull apart and clean off the old lube and then use the AC Delco synthetic grease.

 

[Summajet]

I will check the rubber trans. Mount and if I remove the spline I will mark it.

 

[mijohnst]

I'd say check out your u-joints first. Cheap and easy to do. I just recently did this to my Yukon and it fixed the issue that you're having. Also, make sure you buy the OEM version. In my experience, they fit better than the knockoffs.

 

[Summajet]

I was thinking to check the u-joints first. If needed I plan on using the Oem u joints.