Drive Shaft problem

1959 - 1978, M151, M151A1, M151A2, Technical questions and discussions, regarding anything related to the M151.
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Data Plate
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Drive Shaft problem

Post by Data Plate » Sat Jul 04, 2009 4:08 pm

Ok i installed a m151 engine into my a2 today heres the problem. The front drive shaft went in without an issue but the rear one seems to be a tiny bit to long to bolt it in. Is there a difference between the A1 and A2 rear drive shafts. Im trying to use a a2 drive shaft but the motor is an a1. What to do next????


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Re: Drive Shaft problem

Post by Fil Bonica » Sat Jul 04, 2009 5:50 pm

All driveshafts are the same as far as I know. If I were to bet the motor/transmission is mounted too far back or for some reason the rear diff is somehow mismounted. Maybe when all the body rework was done they tweaked things too much.
Dont know if this helps but it might help to put you in the right direction.

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Re: Drive Shaft problem

Post by Data Plate » Sat Jul 04, 2009 6:56 pm

Fil thanks i was also thinking that maybe if i loosen the motor mount bolts i can bring the engine forward maybe 1/4 inch thats all i need. Kenny

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Re: Drive Shaft problem

Post by NW42 » Sun Jul 05, 2009 5:54 am

If you body has been cut and rewelded the driveshaft will probably need to be shortened as well. I've run into that on several cut M151's

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Re: Drive Shaft problem

Post by Data Plate » Sun Jul 05, 2009 6:54 am

I measured the original drive shaft and it measures a little under 40 1/2 inches. When i measure mine from from to rear mounting pounts its exactly 40 inches. So i guess there is the problem. Ill have it cut to 40 inches and hopefully ill be OK.

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Re: Drive Shaft problem

Post by Fil Bonica » Sun Jul 05, 2009 8:03 am

Before you get in to special driveshafts I would check to see if the engine transmission is in the correct position. There should be plenty of give to the shafts if they are correct. They really shouldn't be tight.
All of this is predicated on the fact that the body was not a reweld.
Good Luck
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Re: Drive Shaft problem

Post by Data Plate » Sun Jul 05, 2009 2:25 pm

This mutt was cut so i think there is my problem. i tried loosening the rear differential to get some play to put the drive shaft in but i still dont have enough room i guess my only option is to shorten the drive shaft.

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Re: Drive Shaft problem

Post by Data Plate » Thu Jul 16, 2009 5:45 pm

I had the drive shaft cut alittle under 1/2 inch and it fits fine.

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Re: Drive Shaft problem

Post by Donald Van Holt » Sun Oct 18, 2009 6:01 am

I have an uncut A2, but I understand that when they re weld a cut jeep the overlap the sheet metal about 1/2 inch

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Re: Drive Shaft problem

Post by lten1063 » Wed Oct 28, 2009 4:33 pm

Reweld MUTTs will give you problems when bolting on componets like the drive shaft & top bow system because the support rods from the bow to windsheils will be a bit longer/shorter same as the drive shaft.

When they reweld MUTTs back together some issues are missed which causes problems further down the road in restoration.
I have seen all kinds of methods like over lapping, metel blockes all along the cut seam or a metal strap weld in place all around the the cut seam. Most of the metal is a heaver/liter gage than the gage of the body. But the one most inportant issue is missed is the frame and hat channel because thats where all the weight, stress and support is and not done properly will start tearing in those areas which causes the rest to fall.

One day I think I will show how to properly reweld a MUTT back together because I have a parts only MUTT that is a side to side cut and when done with it I will put the reweld parts back correctly with pics to show the progress. This method will work on X cuts (more work involed) as well as side to side cuts.

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Re: Drive Shaft problem

Post by 23learjet@gmail.com » Thu Apr 15, 2021 5:43 pm

I have a 1970 uncut M151A2. One of the front bolts broke on the drive shaft, then a second one and the drive shaft hit the ground. The shaft isn’t straight now. I’m trying to buy a nos drive shaft. Are they all the same? I think the part number is 7368801.

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Re: Drive Shaft problem

Post by markrdje » Fri Apr 16, 2021 12:18 am

In my inspections on my 151, I found the nuts in the u joint loose, so I installed these special lock washers, as well as putting lock tight on the u bolt threads.I think the lock washers were called norlock washers? I'll have to do some digging to find the proper name.Fastenal is where I bought them.
I think there places that straighten drive shafts.
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Re: Drive Shaft problem

Post by Rickf » Fri Apr 16, 2021 1:33 pm

All of the M-151 shafts are the same, yes. That is the fronts are the same and the rears are the same. They are different from each other. I would not try to have one of those shafts straightened, you are working with compound angles, that is why the u-joints look like they are out of phase but they actually are not. Straightening that shaft would cost a lot ore than a new one.
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Re: Drive Shaft problem

Post by markrdje » Fri Apr 16, 2021 1:50 pm

I forgot to say I had the driveshaft balanced too
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Re: Drive Shaft problem

Post by Crux444 » Thu Apr 29, 2021 3:36 am

markrdje wrote:
Fri Apr 16, 2021 12:18 am
In my inspections on my 151, I found the nuts in the u joint loose, so I installed these special lock washers, as well as putting lock tight on the u bolt threads.I think the lock washers were called norlock washers? I'll have to do some digging to find the proper name.Fastenal is where I bought them.
I think there places that straighten drive shafts.
You are referring to NYLOK nuts, nit washers. They have a nylon collar at the top of the nut that grip the threads of the bolt. Using these eliminates the need for a lock washer. Did you get CAD plated fasteners? They are proper MIL-spec and will resist corrosion vs. bog standard hardware; worth it for the underside components that are exposed to road grime and water.
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