rear end tag numbers

[68ford]

I have the numbers from the tag on my rear end. I think from the vin numbers it is a 3.70 Ford rear end. I wanted to double check if anyone knew the code for the rear end tag numbers. They are as follows:

WDM-U
3 70 8CD 302

Also my rear end was locking up during sharp slow turns. I put in 80W90 gear oil and some of the limited slip additive. The additive seems to be loosening up the gears a little. Is this common if there is no additive in there? I may try to add some more if it doesn't get any better.

[Nefarious67]

3 70 is indeed 3:70 gear ratio non locking. If it were a locking differential it would have been 3L70. WDM-U I believe is the plant it was made at, not sure though its been to long since ive read about it. As for locking up, I dunno if its wise to used locking additive in a non locking rear end, someone else will have to answer that one. Something is probably wrong with the spider gears in side the diff to cause it to lock up.

[68F250]

Yep, 3.70 conventional, 8 3/4" ring gear, manufactured in the 4th week of March 1968. WDM-U is the model code, 302 is the plant code.

Here's more than you ever wanted to know about Ford rearends:
http://www.kevinstang.com/Ninecase.htm

[68ford]

that is an informative website. i was told by a tranmission guy that the limited slip additive was for rear ends that were not locking diff's. i hope that was correct. it seems to be slipping more now.

at first i thought it was a locking diff the way it grabbed. i think maybe the oprevious owners just put gear oil in without the additive.

[heep70]

The additive is for rearends that have clutched locking diffs. Like PowerLocs and Traclocs. Its called a friction modifier. You do not need it for an open rearend. It wouldn't help anyways.