2nd Gen Non-Engine/Transmission Two Piece Drive Shaft - How "Slippy" Should Slip Joint Be?

[Bruce Banister]

I have a question regarding how “slippy” the center slip joint in a two-piece drive shaft should be? My 2001.5 3500 (5 speed, RWD, 205,000 miles) has developed a little “tunk” sound / feeling that randomly occurs just after the clutch is fully engaged and the truck is accelerating during a start in first or second gear. Looking things over from underneath revealed no visible slack in the u-joints, the axle u-bolts are tight, the center bearing runs smooth though the rubber is deteriorated, the rear end (posi) has a little play in it but nothing too outrageous. So I had no specific evidence as to what the problem is. I hate throwing parts at undiagnosed problems but given the mileage on the truck and browsing the TDR forums for guidance, I ordered three u-joints and a center bearing and set to work.

With the shaft out on the floor of the garage it took 45 minutes of careful to moderate (OK, some heavy) hammering to separate the rear shaft and slip yoke from the “slip” joint spline behind the center bearing. The rubber boot covering the joint was good, there was grease on the splines and there is little apparent corrosion on the shaft / yoke splines. However, the blue plastic coating material on the rear facing male driveshaft splines was peeled loose on two of the spline ridges. I believe that was the cause of the bind that required the extensive hammer massage to get the two shafts separated. I shaved off the loose blue material and relubricated the splines. At this point the slip yoke/driveshaft spline joint is still *very* tight and don’t want to continue the shaft rebuild until I understand how much and how easily the slip joint should slip. Given that the front half drive shaft is only positioned in-place by the center bearing and its relatively delicate rubber suspension, it would appear to me that any front/rear motion of the rear half of the shaft (during reinstall and on the road running) must be handled by a very slippery mid-shaft slip joint. I avoided applying heat to the slip joint to separate it initially so I wouldn’t damage the blue coating. The coating either deteriorated over time or when I separated the slip joint. The only sure thing is that it was frozen tight on removal. What is the function of the coating? Can it be scraped or peeled off and the splines run directly greased with no ill effect? Please give me the benefit of your collective wisdom and experience regarding what I can reasonably get away with regarding my non-slipping slip joint. I would like to get another 5 years or so out of the truck without forking over the cash for a new driveshaft assembly if I can. Then I can find out if I chased the “tunk” away or if it’s really going to get expensive (clutch disc internals, rear end, etc.) 

 

[B.G. Smith]

I don't recall ever seeing the blue coating you refer to. Sounds like someone put something in there that shouldn't have been. Are you the original owner? The slip joint should be easy to move in and out. bg

 

[Wayne M.]

The blue material on the male splines is a Teflon like coating to act as an anti friction coating. This coating is commonly seen on many trucks up to the big boys on various splines and bushings. The rear shaft yoke with the female splines should fit right on and glide in n out like you know what. Some shafts have a master spline but not commonly seen here. The issue you're describing could be some damage from overloading or improper previous assembly. I've never seen this coating wear out. Did you find any other issues like frozen joints? Are the splines twisted? Was the shaft assembly in phase when you found it?

 

[Wayne M.]

To clarify, I can't remember the last time I had a 2 gen shaft apart. I am speaking generally.

 

[S.Morris]

The coating is more of a permanent lubricant(kinda like Teflon 5th wheel wear plates). It makes tolerances close, gives somewhat of a cushion.

Your "tunk could very well be coming from the issue you have found. Can you see any wear on length of the splines ----_________-------. If you can see or feel any appreciable wear it can cause the shaft to stick under torque in its most used spline area. It is hard on the hangar bearing, pinion bearing as the movement of the shaft is not following the movement of the axle under torque and spring compression.

You can clean it all off and insert to running depth and see how much play you have twisting one piece of shaft while holding other stationary. If it is excessive than the slip and spline can be replaced on your shaft at a dshaft shop.
If the spline is worn some , the edges (that would stop free movement length ways) can be sanded/ground more smooth with a thin cut. This however will only buy you a little time as the accompanying wear of splines on female side will, in time, make matching marks again.

So clean it up good and grease with good moly grease(not too much to cause hydraulic locking). It will last as long as it lasts.....This is one place where a manual transmission contributes to increased wear over an auto.

 

[ewcmr2]

A friends duramax driveshaft slip joint makes noise, he disassembles and greases it every 10,000 miles.

 

[Wayne M.]

A friends duramax driveshaft slip joint makes noise, he disassembles and greases it every 10,000 miles.

Well there's a couple of issues right there!

 

[Bruce Banister]

Thanks to all of you who offered insight / experience on my bound up slip joint problem. Several of you asked questions to guide my thinking - responses in order are:

I’m the second owner of the truck since 28,000 on its odometer. The truck was used by a business and probably worked hard but not abused as far as I can tell.

The yoke / shaft does have a master spline so it can’t be assembled incorrectly. The joints all look to be original and I marked shafts / yokes / etc. so everything goes back in phase and balance. There have been no vibration issues across the 180K we’ve used it pulling a couple of different 5th wheels. We down-sized a couple of years ago to a 20 foot TT (the driver grew weary of handling 13,000 pounds on the road before the truck did).

None of the joints were frozen but it’s a reasonable maintenance item to cover with over 200K on the chassis. The splines don’t *appear* to be twisted but something is amiss in there.

My battle plan is to finish peeling / shaving the blue plastic stuff off the spline, check for burrs / rough spots, grease it well but gently, and see if it goes back together in slippy / slidey mode. If the “tunk” is gone then we call it a win and see how long it lasts. I can live with a tunk short term – its those “broken down on the side of the road with the RV on the back blues” I don’t want to be singing. If the joint won’t slide smoothly or quietly then we start to investigate costs of drive shaft shop vs new assembly.

I’ll post back results when I get it done.

 

[SAndreasen]

My slip joint was making a clunk as you describe I bout a grease needle that would fit in between the splines and greased it good helps tighten it up for awhile then have to regrease it

 

[Bruce Banister]

OK - So I used an xacto knife and peeled/scraped the blue Glidecote off the male slip joint splines, deburred the female splines, greased it up with red Lucas EP Lithium and stuffed it back under the truck and went for a ride. The “tunk” just after clutch engagement was gone but there was noticeable looseness in the driveline due to the loss of the cushioning effect of the Glidecote. After a consultation with Inland Truck Parts in Austin, TX I opted to have them rebuild the drive shaft assembly. They cut the male spline off the front shaft, welded on a new one, pressed on my new center bearing and installed my three new U-Joints and rebalanced the whole thing. I reinstalled and all is good once again. My wallet is $685 lighter but I am more comfortable it will hang together for as long as I need it to.

 

[SSage]

Ouch, at that price I would go one piece aluminum shaft and eliminate the center support bearing. I just did my 1995 dually 2 piece drive shaft and I couldn't justify spending for a new shaft though, it was in decent shape with good splines and etc. My parts bill was only $189 for 3 greasable u-joints and a support bearing assembly. Afterward I was hoping for no clunk going into gear, but my Dana 80 does have some play in it. Runs so much smoother though, my center bearing was loose. I had a body shop do the labor, they charged me $134.00. I have never tried replacing a center bearing, didn't want to learn.

 

[GAmes]

I had my driveshaft modded at Inland after my G56 conversion and also had all the u-joints and center bearing replaced 300k later. They do excellent work and I don't mind the price tag. You can get spicer parts for less on line than they charge, so if I manage to get to the 300k mark again, I'll call them and see if they will install parts I provide.

 

[Mingoglia]

I wouldn't expect a slip yoke to clunk, and yes, the blue stuff is anti-seize. Typically thunks like you're seeing are u-joint. With that being said, everything I've known about drivetrain thunk has gone out the window with my 4th gen. It clunks when put in gear like no other vehicle I've own, new from the factory and the others I test drove were the same. Seems to be even worse on trucks with numerically higher gears.