Replace or repair front drive shaft in 71 4X4

[Montana71-F100]

I can move my front drive shaft up and down easily at the joint where the splines go in and out and there's a loud "clunk" every once in a while when I drive so it needs attention. Is it better to replace it or have it repaired and where is a good place to buy one or have it repaired?

Thanks

[Montana71-F100]

Thanks, Fordman, I'll post in the "Parts Wanted" section and see if anyone has one.

[cep62]

There are places that can replace the splined end and yoke.
thats more cost effective than new.
Check your local area for drive line or machine shops.

[papabug71]

There are places that can replace the splined end and yoke.
thats more cost effective than new.
Check your local area for drive line or machine shops.

I agree with everything cep62 said. I had an old jeep driveshaft re-splined & balanced for $50 bucks, & they did it while I waited.

Look for a local machine shop and/or a driveline shop.

[Montana71-F100]

Thanks everyone. I removed the drive shaft and took the end cap off of the yoke and found that there is a groove worn where the seal rubs against the shaft that has the splines. I was hoping to get a Speedy sleeve to put over the groove and replace the seal but the parts store I use can't find one the size I need. They don't have any information on that drive so they couldn't find a seal either. I tightened the cap on the yoke in hopes that I could squish the seal enough to fill the space. I think it's a little better but it looks like the yoke and spline will have to be replaced or I'll have to limit my speed in 4 wheel drive to about 15 MPH. I don't use 4 wheel drive very often but it's nice to have when I need it like backing out of an icy parking spot. I'll try the "drive slow" option for now.

[cep62]

It's amazing how sloppy they get and still hold together.
aside from vibration at speed it should last a long time.

[Montana71-F100]

Thanks, Cep62, that's encouraging. The big thing I worried about was a loud "Clunk" every once in a while. When it's cold it was several times in the distance of a block. After tightening the cap it was once in about 4 blocks. It wasn't very cold though, (around 30 degrees). At around 15 MPH it never happens.

[Montana71-F100]

Now I'm not so sure the "Clunk" is coming from the drive shaft. I tried driving very slowly, about 3 or 4 mph in 4 wheel drive and still heard the clunk only not as loud, then I unlocked the hubs and kept the floor shifter in 4 wheel drive so the front drive shaft would spin and it didn't make any noise even at 25 mph. Could the "clunk" be coming from the transfer case and if so, what could be causing it?

[cep62]

If you're driving on a hard surface in 4wd the drivetrain can bind up, when it releases it can make a clunk.
also the outer drive axle ujoints can fail and make noise.

[Montana71-F100]

It happens on pavement and on snow. The owner's manual states that you must use the same size tire and tread design on all four tires. Mine are the same size but the tread isn't identical and some are worn more than others. I wonder if that has something to do with it.

[cep62]

It happens on pavement and on snow. The owner's manual states that you must use the same size tire and tread design on all four tires. Mine are the same size but the tread isn't identical and some are worn more than others. I wonder if that has something to do with it.

It might.
Try walking along side it with some else driving and see if you can see what is making the noise.

[Montana71-F100]

Try walking along side it with some else driving and see if you can see what is making the noise.

I was trying to figure out how to do something like that too. You have to be underneath the truck to see anything. I rigged up my video camera under the truck and pointed it to the slip yoke and U-joint. I couldn't see anything unusual but the sound was more like a piece of metal hitting a pipe than the "clunk" I heard in the cab.

When the hubs are in and the transfer case is set to 2 wheel drive, the front differential is turning the drive shaft and I hear the noise but not as loud. When the hubs are out and the transfer case is set to 4 wheel drive, the transfer case is turning the drive shaft and I don't hear the noise at all. That made me suspect the front differential. I replaced the U-joints not long ago and they are tight but I can rotate the drive shaft about an inch where it goes into the front differential. Should it have that much play?

I may end up putting the truck on blocks and seeing what I can find. I hate to spend money on the drive shaft if that's not the problem.

[Montana71-F100]

I have a new theory on where the "clunk" is coming from. After overhauling the engine after it sat for 12 years, I started fixing leaks. One of them was the front differential. The leak turned out to be coming from a crack in the axle housing next to the differential. When I took the front cover off I found that it a large dent in it that had been pounded and there were some partially broken teeth in the ring gear, probably from the impact from whatever hit the front cover. Whoever owned the truck between when it was new in 1971 and 1972, when my dad bought it, must have hit something very hard. Since just the tips of a few teeth were chipped off I didn't think there would be a problem. Now I'm wondering if the "clunk" is from the pinion and ring gear slipping once in a while. I hope I'm wrong and the solution is simple!

[Montana71-F100]

The clunk was coming from a worn out u-joint in the right front driving axle.

[Bob]

The clunk was coming from a worn out u-joint in the right front driving axle.

Tah Dah...!!

Congratulations on finding your clunk maker...!