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73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: chrpmaster on February 23, 2009, 09:04:14 pm
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Does anyone know what the final drive gear ratio was on an 82 1/2ton 4wd with 700r4 and 6.2 diesel? I have a line on one for parts and was thinking it would be a good source for my rear axle swap project I am planning for this summer.
Thanks
Andy
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To know for sure you need the axle ratio. I think the 700R4 OD is close to .7:1. For example if the ratio turns out to be 3.42 times that by .7 and final drive is 2.394
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Your final drive ratio will be vehicle specific. The only way to truly know for sure is to pop the cover off the rear end. You can look in the glove box and check the spid label but that's no guarantee. Typical ratio was 3.08:1
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Thanks guys for your help. This is a truck I used to own until I lost my mind and sold it cheap to my little brother. He proceeded to let it rust itself to death from neglect and misuse over the last 5 years. Now he just wants to take it to the dump and get paid for the scrap. I am trying to salvage anything still useful off of it that I can hide from the wife thus the question about the final drive. He lives about 30 miles from here and the truck has not run for a couple years so I will have to make a trip out there to check it out.
I hope the rear axel is in decent shape cause when I was pricing the cost of changing the ring and pinion in my truck the parts guy reminded me there were two different carriers used depending on ratio. Mine is currently a 4.10 and to get down to 3.40 or below I need to change to the other one. That adds like $300 to the cost plus the ring and pinion. So I started shopping for a donor axle and thought of him.
I suppose the good news is I may have lots of good parts available if anyone needs anything. Including a nice 6.2 liter diesel engine and related stuff. It won't happen for a couple more months but hopefully I can get something done this summer. My daughter graduates from high school in June so after that I might get away with towing it over here and starting the disassembly.
I'll keep you posted on what I find.
Andy
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If you can jack it up, here's how you can check. Chock one tire and put a chalk mark on the free tire. Also, put a chalk mark on the pinion yoke and housing. Put the tranny in neutral and rotate the driveline enough times to make the tire rotate once. Count the turns of the yoke and that's your ratio. You'll have to look it up to get it exact but you get the idea. You can tell the difference from a 3.08 and a 3.55, or whatever, pretty easily.
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I was out to his house over the weekend and crawled under the 82 donor to look over the rear axle. It looked decent - normal surface rust but nothing like rust through or anything. The bolts attaching the axle to the springs will probably need cut off but no surprise there. It is a 10 bolt.
He did say that he had a leak in the left axle and something leaked on to the brakes that made them grab. he said he just cleaned off the brake shoes a couple times a year and it was fine. Yes I know he should have fixed it but thats how the truck got in such bad shape as it is now. Any idea what would be leaking? Also where is the seal that would be leaking whatever onto the brake shoe?
If I use this axle I plan on rebuilding it and replacing brakes, brake lines and probably opening up the diff to clean it up and replace the oil. Anything else I should be aware of?
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If the axle seal is leaking it will leak gear oil onto the shoes.
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If the axle seal is leaking it will leak gear oil onto the shoes.
Is that seal inside the diff or out near the wheels?
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At the end of the axle tube, there is no internal seal.