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| | | Joined: Feb 2009 Posts: 66 Wrench Fetcher | | Wrench Fetcher Joined: Feb 2009 Posts: 66 | I have a 1970 GMC 1500 and I don;t know which rear end I have. I don't know where the vindication plate is. All I have found is the GVWR plate, and it has what looks like a the vindication number, but on a code page I found, most of my vindication numbers aren't even choices. I do know that it has a TH 400 right now, but since I have no vin. plate, I don't know what is original and what is not (the engine was not). I guess my question is stiil what is my rear end ratio most likely to be? And where might I look for the vindication plate?
"So this year, I am upgraging my policy of zero tolerance to one of SUB-zero tolerance, which is MORE than zero." -Principal Jindraike
| | | | | Joined: May 2006 Posts: 8,351 'Bolter | | 'Bolter Joined: May 2006 Posts: 8,351 | There should be a code stamped on one of the axle tubes. Most likely, you have the 12 bolt if it still has the original rearend.
Bill Burmeister
| | | | | Joined: Apr 2009 Posts: 431 Shop Shark | | Shop Shark Joined: Apr 2009 Posts: 431 | catch the oil as you pull the cover, wipe it off, and read the nunbers on the ring gear. the guessing will be over | | | | | Joined: Mar 2004 Posts: 3,068 'Bolter | | 'Bolter Joined: Mar 2004 Posts: 3,068 | The plate is inside the glove box,
Scott | | | | | Joined: Oct 2005 Posts: 1,317 Shop Shark | | Shop Shark Joined: Oct 2005 Posts: 1,317 | You might save yourself some work by just jacking up one side of the truck.....if it's an open (not limited slip) you should be able to spin the raised wheel. Make a chalk mark on the tire, make a mark on the diff yoke. Get a helper to spin the tire 10 revolutions while you count the revolutions of the yoke. Record the yoke revolutions and multiply by 2 and divide that number by 10. That should be the first 2 numbers of your R&P ratio.
So why not just spin the tire once? With just one spin you will be able to figure the 1st number of the ratio but will have to eyeball what percentage of a revolution the yoke made. Is it a 3.00, 3.28, 3.38, 3.42, 3.50, 3.73 or a 3.90? By spining it 10 times you get the first 2 numbers of the ratio. Example: Ten tire revs =17 yoke revs times 2 (because only one wheel is turning) divided by 10 gives you 3.4.....more than likely a 3.42 R&P.
Granted, pulling the cover is going to give you numbers to work with....but it's also going to create additional work/mess and you'd better know which numbers to use to make your calculations. This process makes it easy in a junkyard to determine the R&P ratios without having to grapple in the dirt!!!!! Hope this helps.
Dave
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