Inner Upper A-Arm Shaft Question

[Bob B.]

Hi all,

I am trying to attach the upper A-arm on my '57. The shaft is a repro, so I'm not sure if this is the problem or not, but I can't get it to screw in all the way on either side. The front hole on the crossmember piece where the shaft goes in is bigger than the rear hole. When I try to install the shaft, the threads for the grease fitting nuts slide straight through the front hole. Then the threads that match the inside of the hole screw nicely and then the middle smooth part of the shaft slides through until I get to the rear hole. The rear hole, being smaller, allows the shaft to screw in, not slide, with the threads for the grease fitting nuts, but when the threads that are supposed to screw into the rear hole hit, it stops because the rear hole is too small.

All I can think of is to use a die on the shaft and thread across the threads that are supposed to screw into the rear hole and make them the same size as the threads that are for the grease fitting nuts to get it to screw in. I don't want to tap the rear holes. I hope my description makes sense.

Any other suggestions?

Thanks,

Bob

[Joe M.]

Re: Inner Upper A-Arm Shaft Question

Critical to read the ST-12 manual on this procedure. Threaded shaft goes in with difficulty is normal. Supposed to be some oversized threaded shafts as well.

Do not do anything else until you read the article or manual as you may damage the threads and make them useless.

This was posted in several places by our own Tom Parsons.

Everything you ever wanted to know.

http://www.chevytalk.org/fusionbb/showtopic.php?tid/218134/

[Bob B.]

Re: Inner Upper A-Arm Shaft Question

Hi all,

Just wanted to see if anyone can get some measurements on an original inner upper A-arm shaft? I read over the ST-12 and looked at the website with Tom Parson's great instructions on it. He shows having to use a breaker bar to get the shaft installed, but he also mentions that the replacement shaft is 0.008 over in case of wear on the female part the shaft screws into.

My shaft doesn't seem to even want to go into the female part sufficiently to even catch the threads to even muscle it in with a breaker bar. Maybe my female part isn't worn enough to need the 0.008 oversize? Once I'm done, I'll hopefully look back, as always, and say it was no big deal after all. But before I do this, I want to make sure that I don't tear up the female threads.

So, does anyone have measurements of an original shaft to correspond to mine? I tried to upload a pic, but the latest changes to the TDB don't allow me to do this with a Mac. So, starting from the end with the large thread size, my measurements from outer threads, inner threads, smooth center part of shaft, inner threads and outer threads are 0.744, 0.792, 0.758, 0.763 and 0.737".

Thanks,

Bob

[Donald H.]

Re: Inner Upper A-Arm Shaft Question

So I don't know if it is a true original, but here's a picture of one that came off my 60. It was pretty worn. The measurements I get from it are 0.744, 0.780, 0.722, 0.754, and 0.735. Sure looks like the 'funky threads', the ones that screw into the bushing, on yours are more that .008 larger than what I am measuring.

I used a Paragon kit and Tom Parson's instruction and recall that it did take some force to get the new shaft into the A-frame bushings, but not to the extent you are describing.

Don


Upper inner pivot shaft.jpg

[Richard M.]

Re: Inner Upper A-Arm Shaft Question

I had this info recorded from a original from a '59.
P7060048.jpg P7060049.jpg P7060052.jpg