Time Required to Swap Rear Differential

[glcaines]

I have a rebuilt differential to replace the existing rear differential in my M151A2. I am currently unable to replace it myself. A local garage I trust will do it but they would like an estimate of the time required. I'm guessing 3 hours max. Does anyone else have a more accurate estimate?

[csmith]

I DID MY FRONT A FEW YEARS AGO FROM THE FLOOR AND IT TOOK ABOUT THAT LONG, A GARAGE WITH LIFT AND JACKS SHOULD BE ABLE TO DO IT IN LESS TIME, MY GUESS 2 HOURS MAX.

[Hambone]

I agree with the 2 hours max, problem is, they'll throw in a couple smoke breaks.

[rickf]

Two axles and a driveshaft plus the three bolts on the diff. I have done it several times on the floor using a floor jack in under an hour. This is using an impact wrench for the bolts on the diff. Putting bolts back in I spin them in with the impact but tighten them with a torque wrench.

[glcaines]

Now, I have more problems. I went ahead and filled the rebuilt differential with 85/140 lube when it was easy to pour in while sitting on the floor. Unfortunately, lube is now running out of the pinion seal into a puddle on the floor where it is resting, so I will need to replace the pinion seal before installation of the differential. The differential was a government rebuild with a date of 1982 on the tag. Fortunately, there is no sign of leakage from the other two seals, although they may start leaking after installation since the seals are 41+ years old. After replacing the seal I may go ahead and install the differential myself. I hurt my wrist and that is why I was going to let someone else do the swap, but it is back to about 75% now and this is really a simple task.

[fowlercal]

Replace all the seals before installing. They all come in one kit and easier to do while out.

Cal

[rickf]

What year is your A2? I ask because the early A2's had issues with the rear frame cracking around the diff mount and there was a MWO for that with some brackets to be added on. I have the brackets but not the bolts, They would be easy enough to source. Is the pinion pushed all the way into the seal?

[glcaines]

My A2 is a 1977 according to what I've been able to find out with significant help from Ken. And yes, it appears that it was assembled correctly. I haven't done any work on it yet as I'm waiting on the new parts. I might go ahead and pull it apart tomorrow if my wife will let me work on it on Christmas day. Probably not.

[halftracknut]

I'm with rick on this one .....My flat rate book gives 51 minutes on diff swap.... htn

[glcaines]

Well, I took everyone's advice and replaced all of the seals. Very interesting results. The rear pinion and the sides for the axles all had sleeves installed, but the rubber on the seals were completely dried out and crumbling. Easy fix installing the new seals and since the sleeves were perfect, no need to replace them. The big surprise is that the main front pinion did not have a sleeve installed, but had a seal that was designed to be used with a sleeve. The rubber on this seal was not deteriorated like the others. There was a large gap between the pinion and the rubber on the seal. This was a rebuilt differential still sealed in the original packaging from the military that I purchased from SECO. I had to cut it out of the foam packing inside the box. A sleeve was installed on the pinion and a new seal installed. I've only driven it for ~30 miles or so, but so far it is now absolutely tight with no sign of leakage. I would advise anyone purchasing an NOS or rebuilt surplus differential to go ahead and replace all seals before installing the differential. I just hope the seal and missing sleeve problem in my new differential is the only problem. At least is is much quieter than the original.

[rickf]

I have found that NOS parts like diffs, transmissions and engines are not always what they seem to be. And military rebuilds are even worse. Some military rebuilds are just plain junk. The NOS stuff is all built on contract and in a hurry so you get what you pay for basically. In the military if they got a bad engine they simply pulled it out and put in another one and sent the bad one back to supply. Where it would have been sent for a rebuild by private Dumbo. Or just thrown in the DRMO pile.

I know this sounds harsh but did you check the backlash and pinion preload on that diff before installing it?

[Horst]

I can only agree. My government rebuild engine (which I had installed while servicing the original one) had a lot of crud behind the freeze plugs which eventually failed after some time because they were rusted from the inside.