Jack differences

[Tom L.]

My '70 jack is pretty rusty. I'm debating the restoration of my original vs. buying a replacement. I found a replacement with an acceptable date (I think) that's in good shape; however, the threads are different. My original has fine threads while the one I'm considering purchasing has coarse threads. What's the difference b/t the fine and coarse threaded jacks? Is the coarse threaded jack correct for a '70 or could the coarse threaded unit be from an '80? Thanks.

[Joe L.]

Re: Jack differences

My '70 jack is pretty rusty. I'm debating the restoration of my original vs. buying a replacement. I found a replacement with an acceptable date (I think) that's in good shape; however, the threads are different. My original has fine threads while the one I'm considering purchasing has coarse threads. What's the difference b/t the fine and coarse threaded jacks? Is the coarse threaded jack correct for a '70 or could the coarse threaded unit be from an '80? Thanks.

Tom-----

Is the replacement jack you found otherwise identical to the original jack in all aspects of configuration other than the jack screw thread type? The GM #3958710 jack was used in PRODUCTION only through the 1979 model year. It was still manufactured for a short while after that for SERVICE, but I think it would be unlikely to find a 3958710 jack with a 1980 date code.

[Tom L.]

Re: Jack differences

Joe,

It looks to be identical but for the threads on the screw. Does the coarse thread unit have a different part number than the fine thread jack? Thanks.

Tom

[Joe L.]

Re: Jack differences

Joe,

It looks to be identical but for the threads on the screw. Does the coarse thread unit have a different part number than the fine thread jack? Thanks.

Tom

Tom-----


I'm not familiar with a change in threads. It may be that the 3958710 went through a change in specifications for the jack screw at some point. I believe that the replacement jack used for 1980-82 had a different configuration that the 3958710.

[Dan H.]

Re: Jack differences

Hi, just wondering about a jack I had in my 64 which is totally later than the correct one. It is dated 9J27, has a warning sticker on it but I can't find a part number so not sure what it fits. Has a fine thread screw, original paint etc. The whole jack is longer than a 64 jack. Are there any other ID marks on these later jacks? Thanks,
Dan

[Chuck S.]

Re: Jack differences

My '70 jack is pretty rusty. I'm debating the restoration of my original vs. buying a replacement. I found a replacement with an acceptable date (I think) that's in good shape; however, the threads are different. My original has fine threads while the one I'm considering purchasing has coarse threads. What's the difference b/t the fine and coarse threaded jacks? Is the coarse threaded jack correct for a '70 or could the coarse threaded unit be from an '80? Thanks.

Is the date stamp the same format as your original jack? Depending on your build date, the date format should be 9* or 0*, where * is an alphabetic letter for the month.

[Harmon C.]

Re: Jack differences

1980 jacks were dated 0 B 20 0=80 B=Feb 20=day of the month. If the jack has no day of the month on it then it is not a 1980 jack but it could be a 70. I have seen a different thread on some service jacks but they look nothing like an original jack.

[Chuck S.]

Re: Jack differences

...My original has fine threads while the one I'm considering purchasing has coarse threads. What's the difference b/t the fine and coarse threaded jacks? Is the coarse threaded jack correct for a '70 or could the coarse threaded unit be from an '80? Thanks.

OK...Back to your original question: Coarse thread??!! Fine thread??!!

My late 70 jack, and I expect ALL 70 jacks, has 9 acme threads per inch on the screw. A 70 date code will be a single digit ("0") for year, and a letter (A-G) for month.

[Tom L.]

Re: Jack differences

Thanks everyone.