Strange knocking noise while coasting

[thrnelson]

Thanks for the info and ideas. It looks like I should just replace the u-joints. They are not expensive and I was going to replace them this winter as general maintenance in an effort to replace anything that could go bad and leave me stranded. I am going out of town for a couple weeks so I will give an update in about three weeks if this solved the problem.

Thanks again,
Trent

[thrnelson]

I unbolted the straps from the rear u-joint today expecting the drive shaft to push towards the transmission so I can drop it down in the back and then pull it out. However the drive shaft did not move at all. Did I miss a step some place? The only thing that I could think is that I need to put the transmission in neutral first but before I keep experimenting I thought I would ask here first.

Thanks for your thoughts in advance.

Trent

[poboyjo65]

Yes you should have about 1'' of slack that the front yoke pushes up in the trans.

[Lou's Comet]

They stick in the pinion yoke sometimes. Get a pry bar or large screwdriver to pop the rear U joint out of the pinion yoke. First make sure you have the wheels blocked so car doesn't roll, and I would put it in neutral after blocking the wheels, sometimes there is pressure and putting it in neutral will relieve it.

Lou

[thrnelson]

Thanks guys. I will give it a shot tomorrow afternoon. I'm on the east coast.

[poboyjo65]

It can hang like Lou said & usually do somewhat ,but you should be able to look at the front yoke & tell if it is bottomed out or still has more yoke to go in.I would want to inspect that before taking out the shaft. If you car is completely stock it is possible someone got the L shaped part of the 3 pc motor mount on the wrong sides. there is a left & right of these mid mounts & if they get swapped around it would shift the motor back about an inch & if so that would take up the inch of slack of the driveshaft.

[thrnelson]

I finally got back in town and went to finish the U-joints this weekend and once I got the driveshaft out I discovered that the U-joints I bought were wrong. Unfortunately the parts store could not figure out which ones were correct. Has anybody else had this problem or know the parts numbers for the correct U-joints? On a much better note I ordered the CSRP disc brake conversion this weekend.

[SASSY]

A driveline shop may be your best option.
They work with the measurements.
Fred

[Comechero65]

With the 3 piece motor mounts as used on early falcons and comets, here are the intermediate mounts and where they are located. You need to install the correct rubber mounts for each side as they are different. Oriented as in the pic locates the engine farthest back towards the firewall for the most clearance in front of the engine and the zbar sits square to the engine and frame. And gives less projection of the front yoke clearance to the tran. Swapping them the opposit way moves the engine forwards about 3/4" and the zbar will sit at an angle cock-eyed to the engine. Yoke will have a larger projection as well.
Depending on the amount of projection and what rear end you have I have a suggestion on how to reduce the space without altering the driveshaft.


Ron

[Comechero65]

Yes dropping a yoke on the road can be bad as well as surprising. Have had a front yoke come apart once. In my case it made a sudden stop when the driveshaft wrapped itself up in the parking brake cables. Only real damage was to the end of the driveshaft. Corrected that and a new u-joint and it was back on the road. Was a heck of a surprise when it happened. Made it home on a tow truck where it got repaired.
Ron

[thrnelson]

I got the driveshaft out. There was room on the front side once I used a light pry bar on the back. Now I am having a miserable time finding u-joints. The front u-joint has all inside clip cups that are 0.9975" in diameter and outside to outside is 3.1400 on both. The rear u-joint has two cups with a diameter of 0.9980 and two that are 1.1240 diameter that are both outside to outside measuring at 3.2100, all four are inside clips although the two larger ones don't matter since they are bolted down. These however do not seem to exist. Has anybody else ran into this?

[poboyjo65]

If you cant find a driveshaft shop nearby you might try some of the online specialist, here is one for example;
https://www.iedls.com/

Or if you can find an old school type parts house that has an old guy & still has books. I use to get the 2 sized cup ones all the time, we called them bastard u joints.

did you notice how much room was in front? an inch is what it should have, probably get by with a little less. & the yoke needs to slide in the trans easily ,even that last inch.

[poboyjo65]

Here are some near you, let your fingers do the walking
https://www.google.com/search?q=driveli ... 8&oe=utf-8

[thrnelson]

I did not look to see how much space the front yoke had before hitting the transmission before I took it out. I found the old guy at the local parts store and he said the u-joint was discontinued. I checked with my local driveline shop and he says the same thing. Online I found a part number for the front u-joint that is still available in a NEAPCO brand part number 1-3600 that appears to be correct but the rear u-joint with two cup sizes is still a mystery. I will try the place you are recommending. Thanks for the help. I did not expect this kind of difficulty with a u-joint.

[thrnelson]

Here are some near you, let your fingers do the walking
https://www.google.com/search?q=driveli ... 8&oe=utf-8

Great minds think alike. The Cook Brothers place is where I tried.