1967 C20 transmission swap

[jollygreen]

I had originally thought it was a rear differential problem, we heard a lot of...well, just bad nosies from the differental when I took off the rear housing plate, so I kind of jumped the gun and bought a '57 rear end, the mechanic assured me that they were the same, HO72 I believe, anyways, I knew everything worked in my originally rear diff. so I just wanted to take out the spider gears of the old one and swap them with my new ones...to my surpirse, they weren't the same at all. But we ended up taking my rear end apart as well and well, we just couldn't find anything wrong with it, so we steam cleaned all the guts, and they looked great! Put some new oil in there and the same noise came back but not as bad at all.

So now I'm thinking it's the transmission, I have the original 3 speed in there but I heard a popular switch is to the 4 speed 700RH transmission. Am I correct about this? I found one online for about 1k and then another one in town for about 500 installed! I'd like to do the work myself but that's almost too good of a deal to pass up.
Any help and hints y'all could give me I'd be grateful!!!!!
Thanks y'all

[LockDoc]

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I don't very often say this but I think your best bet on this one would be to go to the search box at the top of the page, type in "700r4 swap" without the quotes, click on the circle in front of "67-72Chevytrucks.com and click on the "Google" button. There are a lot of good threads on this swap on the board and some of them are pretty in depth.

LockDoc

[rcrahn]

Sounds like some more diagnosis/troubleshooting is needed to pinpoint the cause of this noise. Before you make your next move check out the entire driveline including the driveshaft, ujoints, wheel bearings, etc....
The gear ratio in the HO72 is 4:10 so an OD trans will help to lower the RPM at highway speeds. $500 installed sounds too good to be true so I would be careful. A remanufactured trans with a warranty is going to run you around $1,000. So move carefully.