CMP Service Issues - Things to Watch Out For

[Phil Waterman]

Hi All

Thought I'd start a new thread with the idea of collecting CMP Service Issues - Things to Watch Out For. Idea to collect known service issues for those of us who drive our CMPs often.

ISSUE-Drive shaft bolts working loose.
Today I was adjusting the brakes on the trucks and as I jacked up the rear of my C60S and turned one of the rear wheels to adjust the brake, heard a clink as something fell on the floor, turned the wheel a little more heard another clink. One Nut One Lock Washer on the floor

could have been a lot worse place to loose these.

Then looking up to see where they came from

the drive shaft flange behind the transmission.

Started checking the drive shaft bolts and discovered that forward ends of both the short shaft and the rear drive shaft all the bolts were loose. This is not the first time I have discovered this on one of my trucks and as I think about it, it always seems to be the forward end of the shaft.

De-greased bolts and nuts replaced the lock washers and put Loctite on all of them and tighten them all up.

Tomorrow I'll check the drive train on the other two trucks.

Found a recurring Service Issue share it with the rest of us.

Cheers Phil

[rob love]

The short shaft between the transfer case and the transmission had the nickname "jackshaft". They constantly come loose on most trucks....constantly on the M135 deuce, the CMPs, the M37s, and I was just tightening the very same bolts on a White scout car the other day.

[hrpearce]

Phil, I solved this problem by using nylock nuts and leaving out the spring washers. I've travelled around eight hundred miles since I registered the blitz.

[Bob Carriere]

While adjusting the linkage for the winch I noticed the loose bolts on the "jackshaft" ...... redid with locktite.

On a separate event also noticed that the big U bolt axle/spring nuts were loose on 3 spots.... so went over all of them with the wrench.

It is so easy to forget that we are not driving modern vehicles that only require servicing every 100K...... you need to love your CMP and service every 1000 miles or whenever you get a chance to get underneath.

[Corey Myronuk]

Originally Posted by rob love

The short shaft between the transfer case and the transmission had the nickname "jackshaft". They constantly come loose on most trucks....constantly on the M135 deuce, the CMPs, the M37s, and I was just tightening the very same bolts on a White scout car the other day.

I overcame this problem in my M37 by changing to all L9 bolts and nuts with a hardened lockwasher.3 years of trail abuse and no probs..

[Phil Waterman]

Hi All

Well to put this problem in perspective, in an unscientific study, 2 out of 3 CMPs may have this problem, after finding the loose Jack-Shaft Bolts on my C60S checked both C60L and HUP. Results of this was both large trucks had loose or not tight drive shaft flange bolts. The HUP didn't but then again it is under a 1000 miles since overhaul.

That other people have had this problem does raise as suggested that these bolts deserve regular checking.

Replacing the bolts and nuts with modern self-locking nuts is a definite option but I have had problems find bolts with the right length un-threaded shanks so there are no threads in either side of the flange to provide a tight fit for the bolts. I have looked several times for drive shaft bolts through truck sources without luck and have had to resort to using grade 8 bolts with 20 threads. But to get these in the right shank length the bolts are too long and have to be cut to length.

The photos below of TASK NO.9 from the Drivers Handbook - It has an couple of interesting points, 1st "These nuts MUST be tightened with a torgue wrench." yet the required tool list at the beginning of the task doesn't list a torque wrench and it hard to get a torque wrench square on to get a true reading because of the universal joint on the drive shaft.
2nd point makes sense in the Military "Report if Loose"

I now consider my loose bolts Duly Reported.

Cheers Phil

[Tony Wheeler]

Stumbled on this HUP/Beaufighter pic recently which may be a new addition. Fabulous pic I reckon.