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#32526 01/14/2003 9:02 PM | Joined: Dec 2002 Posts: 8 Member | | Member Joined: Dec 2002 Posts: 8 | Hi,
I recently purchased a 52 1/2 ton that has been through several owners. The truck has a 250 engine with a TH 350 tranny and the rear end is a 12 bolt, six lug setup. The guy I bought it from doesn't know what the donor vehicle was and I'm having a hard time trying to figure out what my rear end ratio is. Does anyone know the history on 12 bolt rear ends and how I can identify what vehicle mine came out of? What year of trucks carried the 12 bolt rear?
Thanks, | | |
#32527 01/15/2003 5:08 AM | Joined: Sep 2001 Posts: 109 Member | | Member Joined: Sep 2001 Posts: 109 | when all else fails, count the ring gear teeth and divide by the number of pinion gear teeth. thats yer ratio!
Can't help ya with the other questions......... anyone else?
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#32528 01/15/2003 8:27 AM | Joined: Nov 2001 Posts: 58 Member | | Member Joined: Nov 2001 Posts: 58 | BruceW here is a good discussion with explaination to figure the ratio out.
http://www.stovebolt.com/bboard/cgi-bin//ultimatebb.cgi?ubb=get_topic;f=2;t=003825#000000
The 12 bolt rearend for trucks and cars has been inservice for lots of years. If you look on the top side or front of the passenger side tube there might be a GM number? I guess the other question could be, is it really a 12 bolt rearend?
Good Luck | | |
#32529 01/15/2003 8:28 AM | Joined: Feb 2000 Posts: 4,886 'Bolter | | 'Bolter Joined: Feb 2000 Posts: 4,886 | Most all GM rear axles are marked on the housing tube with a letter code. With out knowing what year the axle is it won't do you any good. You will have to go inside and check the ring gear. It most likely needs cleaned and new gear oil anyway. Rotate the ring gear till you find the part numbers and date code. The ratio should be there as well, 41-10, 39-10, etc... With this information you can figure out what and where it came from. Joe | | |
#32530 01/15/2003 7:59 PM | Joined: Oct 2001 Posts: 3,458 Extreme Gabster | | Extreme Gabster Joined: Oct 2001 Posts: 3,458 | The easy way is to jack up one side, rotate the wheel twice, and count the number of revolutions the pinion makes. That is your ratio.
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A lone amateur built the Ark. A large group of professionals built the Titanic. | | |
#32531 01/15/2003 10:31 PM | Joined: Dec 2002 Posts: 8 Member | | Member Joined: Dec 2002 Posts: 8 | Thanks to everyone that replied to my question. I found a helpful tech article at chevytruck.org under swapping out rear ends by Jim Forbes. It looks like the early 70's trucks had either 3.08 or 3.40 12 bolt rear ends. | | |
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