Diagnosing mysterious sound from Tran/Tcase

[legopnuematic]

I haven’t messed with a 205, but I have rebuilt a 208 and 241.

That amount of play in the splines does seem to be more than I would expect.

 

[SquareRoot]

^ thoughts ?

That doesn't look bad. That slight play will be taken up when you torque the retaining nut down. When you put the output shaft assembly back together, make sure there is zero movement in it. If I remember correctly, I was torquing the yoke retaining nut down on the bench and then putting the rear output assembly back in the t-case. I think I got tired of trying to hold the assembly and torquing it so I got frustrated and just tightened it with the impact. And that is what seated it but I didn't realize it until I put it back in and the 1/16-1/8 inch of play was gone along with the vibration.

EDIT: Had to go back and read my thread. Post #63. https://www.gmsquarebody.com/thread...-this-drivetrain-setup-right-now.40197/page-5

 

[squaredeal91]

How about the splined sleeve that cupples the t case to transmission inside the pedestal? They can wear out and make noise. I broke one in 2 once.

 

[chief_shotts]

How about the splined sleeve that cupples the t case to transmission inside the pedestal? They can wear out and make noise. I broke one in 2 once.

My transfer case has a 32 spline female end on the t case that slips over the output on the tranny. No coupler

 

[chief_shotts]

That doesn't look bad. That slight play will be taken up when you torque the retaining nut down. When you put the output shaft assembly back together, make sure there is zero movement in it. If I remember correctly, I was torquing the yoke retaining nut down on the bench and then putting the rear output assembly back in the t-case. I think I got tired of trying to hold the assembly and torquing it so I got frustrated and just tightened it with the impact. And that is what seated it but I didn't realize it until I put it back in and the 1/16-1/8 inch of play was gone along with the vibration.

EDIT: Had to go back and read my thread. Post #63. https://www.gmsquarebody.com/thread...-this-drivetrain-setup-right-now.40197/page-5

So I took the rear output housing out and inspected it. After playing with it for a while I can't see how a impact would have much affect on seating the needle bearing as the yoke pinches the caged roller bearing agains a ledge on the output shaft. And the rear housing pinches the snap ring on the cage of the roller bearing. However I still plan to impact the yoke back on... just have to source some new gaskets... didn't realize they would be such PITA to find/ have to order.

 

[chief_shotts]

Since I last posted here I have done a number of things in hopes of resolving the issue of the noise/ vibration. Here's what I've done:

I wanted to adjust my rear end pinion angle and instead of buying another block with different angle... I convinced myself a shackle flip would be money well spent and then I could shim from there. The shackle flip plus poly bushing was indeed money well spent and the ride quality is far improved.

Next I pulled the rear axle hubs and I inspected ( one had a very bad leak developing). Both hubs had significant in and out play... far from the recommended torque then loosen to zero lash or slightly looser... (they moved close to 1/8-1/4 in in and out. The hub with the leak got new seal and bearings. The other hub got tightened up a bit.

Pulled the rear driveline and took it in to be inspected.. nothing wrong with it but when I pulled the two piece driveline apart I destroyed the Teflon coating on the splines so that stub shaft had to be replaced along with the carrier bearing. Cost me 575ish dollars...

I Also pulled the transfer case... it appeared that last time I installed i didn't like it up wall and ripped the lip of the trans/ case seal letting tranny fluid in the case. I bought a seal pack and then stripped it down to inspect. Everything seamed to be in fairly good shape. The idle gear had a hair too much end play so I bought a shim pack and adjusted to the recommended.001-.002 thou. I also replaced theses bearings as they had a slight bit of corosion/ pitting on the cage.
Everything else in the transfer case was in good condition all bearing appeared like new (they should be since it was rebuilt less than 5k miles ago). Sealed the whole thing back up and back into the truck... this time using studs to help align The case and transmission as to not rip the seal again.

None of this put a stop to the sounds. The only thing that has effected the sound so far has been my adjustments of the rear driveline angles. It is a two piece driveline so I can not only adjust pinion angle but also carrier bearing height. With the current angles as of reacently the sound has become slightly more pronounced and sounds a lot like bearing rattling around right in the trans tunnel area. The sound will change as a modulate the throttle at highway speed. As a i gain speed upwards of 70 mph a drowning hum vibration started to overwhelm the senses.

 

[chief_shotts]

Also two mechanic shops have looked at it. One said it was the transfer case but that they can't work on it because it's old tech. Other shop wasn't convinced it's the case and pointed me towards driveline angles or wheel balance.

I suppose there may still be some perfect angle I haven't yet found that will remedy the sound. I have some shims I will try tomorrow.

 

[chief_shotts]

Any new ideas as to what is causing this ?

 

[squaredeal91]

Did you try driving it on front driveshaft and with rear driveshaft out ?

 

[chief_shotts]

Did you try driving it on front driveshaft and with rear driveshaft out ?

Ended up getting some new pinion shims and dropped the carrier bearing a bit. Went pretty fast and issue appears to be resolved

 

[nmcgowan80]

I'm having a similar issue with my 74' K25.
6" lift on 35s. I have a single rear driveshaft and the pinion/t-case (NP203) angles are matched. I just installed a 1" t-case drop spacer but still didn't fix the pulsing vibrations at 35mph and 55mph.
Looking at replacing the driveshaft with a double cardan CV but trying to rule out other issues first.

 

[bucket]

If the angles are too steep on the joints, it doesn't matter too much if they match. Sometimes pointing the pinion up a bit can resolve the issue.

Has the shaft been balanced?

 

[nmcgowan80]

If the angles are too steep on the joints, it doesn't matter too much if they match. Sometimes pointing the pinion up a bit can resolve the issue.

Has the shaft been balanced?

The front/rear shaft and U joints were replaced a year ago. Less than 1000 miles on them. I removed the rear shaft and tried to run with just the front shaft to narrow the problem down but for some reason I can't engage the transfer case to lock the front tires. But that's a different problem. When I bought the truck a year ago, it was squatted with a 6" up front and a 3" in the back. The driveline was installed at a shop with that setup. I installed 6" skyjacker leafs in the rear to level it out (and make it look better) and I'm 90% certain that's when the vibration started. I've exhausted myself reading up about pinion angles/operating angles etc. so I know that the rear pinion angle needs to match/parallel the transfercase angle in a single cardan setup which I've done with the digital angle finder. Still hasn't fixed the vibration at highway speed. So my options are:

1. take newly built driveshaft in for balancing (seems redundant)
2. replace newly installed u-joints (seems redundant)
3. get tires aligned/balanced (recently done)
4. replace driveshaft with double cardan and shim the pinion to point at the transfer case (not entirely sure if that's necessary yet?)
5. consider pinion bearings or transfercase yoke? (wasn't really an issue before the rear lift was installed)

I'm sure I'm missing some other things which is why I'm here looking for guidance/suggestions before I start throwing time/money I don't have at problems that don't exist. It seems like these vibrations are common but all the threads I've read here have had different solutions.

 

[bucket]

The front/rear shaft and U joints were replaced a year ago. Less than 1000 miles on them. I removed the rear shaft and tried to run with just the front shaft to narrow the problem down but for some reason I can't engage the transfer case to lock the front tires. But that's a different problem. When I bought the truck a year ago, it was squatted with a 6" up front and a 3" in the back. The driveline was installed at a shop with that setup. I installed 6" skyjacker leafs in the rear to level it out (and make it look better) and I'm 90% certain that's when the vibration started. I've exhausted myself reading up about pinion angles/operating angles etc. so I know that the rear pinion angle needs to match/parallel the transfercase angle in a single cardan setup which I've done with the digital angle finder. Still hasn't fixed the vibration at highway speed. So my options are:

1. take newly built driveshaft in for balancing (seems redundant)
2. replace newly installed u-joints (seems redundant)
3. get tires aligned/balanced (recently done)
4. replace driveshaft with double cardan and shim the pinion to point at the transfer case (not entirely sure if that's necessary yet?)
5. consider pinion bearings or transfercase yoke? (wasn't really an issue before the rear lift was installed)

I'm sure I'm missing some other things which is why I'm here looking for guidance/suggestions before I start throwing time/money I don't have at problems that don't exist. It seems like these vibrations are common but all the threads I've read here have had different solutions.

I'm just suggesting to shim the pinion up a few degrees and see what happens.

Yes, the angles are "supposed" to match. But, due to other variables, that sometimes doesn't work for the application. Not matching angles do not always cause a vibration.

 

[bucket]

Also, there's been SOOOO many lifted squarebody trucks that go down the road with no driveline vibrations and no fancy double cardan rear shaft.