M1009 CUCV rear half shafts.

[SimonUK]

My M1009 just failed its annual roadworthy test (MOT) over here because the rear wheels move in and out a few millimeters. Is this a complete diff/axle rebuild or is there thicker "C" clips available to take up the movement in the halfshafts.

Just fitted this axle a couple of weeks ago as the previous diff decided to convert itself to shrapnel pulling out at a junction. (pics to follow). No wear or damage to the 3.08 gears but the carrier just exploded.

Any info greatly appreciated.

Simon.

[NH2112]

I've never seen a C-clip semi-floating axle that didn't have a small amount of axial play. I guess it's possible that the pinion cross shaft is worn enough to allow excessive movement (the axleshafts aren't supposed to touch it, but do slide in and out while cornering), and the same goes for the C-clips themselves and their recesses in the side gears. The only way to find out for sure is to open it up and take a look. From a practical point of view, as long as there's not enough movement to let the C-clips fall out I'd think it'd be safe. I believe these are about 8mm in thickness so a few mm shouldn't really be an issue. Thicker C-clips could be made to take up the slack, but they'd have to be stock thickness in the middle to fit in the grooves in the axleshafts. Is there any way to appeal this? Even if it involved opening up the diff and allowing an MOT tech to inspect everything, it may be worth it.

[DmaxMaverick]

You could place a shim under the C-clip to take up the slack. The inside diameter will have to be the shaft diameter, and the outside diameter will have to be less than the recess diameter. I've done this on my '85 with a 1978 12 bolt, and the axles have play that can be measured in microns. I didn't like the end play on it when I set it up (it was within spec, I just didn't like it). The end result is less floating going on with the side gears and spline. I think (thought at the time) it would reduce gear/spline wear and could reduce internal heat. I must have done something right, as long as it's been in service under hard use.

[RoverIIa]

I'm fairly certain that those shafts are supposed to float axially. That is the reason for having C-Clips and a straight roller bearing. If you can get away with it, apply the brakes when they do the test. This will effectively "lock" the axle-shaft to the axle housing through the brake backing plate. This also works if you have converted to disc brakes, as the shaft becomes constrained at both ends, and the caliper drag will keep the shaft from moving. Most of the trucks that I can remember have end-float in the range of 1-4 mm. If you get into the 5+ mm range, you might have a problem of some sort. Might, not for sure.

Where does the MOT get a specification for axle float?

[NH2112]

Where does the MOT get a specification for axle float?

I was wondering the same thing. Maybe they made a mistake and took the 0.001" end play specs from a full-floater? I know I've never seen any specs for the 10-bolt.

[SimonUK]

Thanks for the replies guys. Took the military manual to the test station and showed the tester the design of the axle. He was happy with that and passed it. The guy actually works with a lot of non standard vehicles so wasn't too phased by the Chevy the way most testers are. Cant complain really about the failure as there were only 3 minor faults on a 25 year old vehicle. He says he regularly gets 3 or 4 year old cars over here that shouldnt be on the road and have failure lists as long as your arm.

The annual MOT test is a pita but it does make sure that all road legal vehicles over here in the UK are in a roadworthy condition. The tester checks almost everything in the vehicle. All aspects of the suspension, steering, brakes, bodywork, chassis, lights, emissions, seatbelts, windshield, mirrors, oil leaks, driveshafts etc etc.

All bushes must be in good order. All lights and accessories must work, no play in wheel bearings, ball joints, steering box etc. brake pipes and hoses must have no corrosion or be perished, brakes must be above a certain efficiency and be balanced. No corrosion within a certain distance of structural bodywork or seatbelt mounts. Exhaust emmisions are tested. Driveshaft joints checked for play and so on.

Simon.

[NH2112]

Speaking of corroded brake lines, the ones on my Ram 1500 are looking pretty bad. I may end up getting a set of stainless steel lines sometime soon and putting them on - I just hope I don't get nailed for them during my annual inspection. The worst thing is 1 whole section of brake line has already been replaced on this truck. It's a damn shame when these 10 year old lines look worse than the original lines on my 85 GMC did. I'd replaced the sections going to the wheel cylinders during a brake overhaul a few years back, and the section from the rear "tee" forward to the fitting under the cab, but everything else looked good.