rearend question

[mfmtb01]

Hey guys,

posted this on the drive line forum but didn't get much help. Maybe someone one can help me. I am trying to find out the differences between 55 & 57 rear ends. What I know is the 57 has a larger outside diameter axel bearing so I suspect the housings are not interchangable. Are the axels the same without the bearings. I also know the 57 has a provision for a drain plug whereas the 55 does not. Someone on the other forum said the 57 had a wider ring gear. Is the 57 rear end stronger than the 55? I have access to a 57 pontiac rearend. I understand they bolt right in. Is this a good choice for a 55 rear end? I am running 300+hp 327 with muncie M-20. Any help/advice would be appreciated.

[a55togo]

not sure if the pontiac is any stronger, but i have heard the olds is. Not to sure if it is a dirrect bolt in as far as changing housings
Ed

[Bob W]

I think the 57 Poncho rear is almost a bolt in. It's stronger but you will have to move the bracket that holds the brake flex line to the housing from the left side to the right side.

Pontiac parts are getting hard to find, if I was going to swap rearends I would look at going to a Ford 9 inch.


Bob

[The Shocker]

I think the Olds/ Poncho rears of 58 -64 are stronger and a bit bigger.My friend had one in his 55 Chevy with a posi and 5.57 gears .In my opinion they look better than a 9 inch Ford ,but as was pointed out earlier, the parts are not as easy to get.I do know that the axle bearings on 58 -64 Olds/Pontiac and big bearing 9 inch Ford are the same part.The gears set for the Olds/Poncho are hard to find and expensive ,and the posi units are nearly impossible to find and very expensive.The only downfall that i have heard of on the Olds/Poncho rear is that the housings are weak .I think the earlier 55-57 rears were used in dragsters back in the day.Until the later style came out.I'd try to find a 31 spline 9 inch Ford to install if i was going to upgrade.Good luck ...

[chevender]

Originally Posted by mfmtb01

What I know is the 57 has a larger outside diameter axel bearing so I suspect the housings are not interchangable. Are the axels the same without the bearings. I also know the 57 has a provision for a drain plug whereas the 55 does not.

I'm told the axles on a 57 are a different length than 55 56. When you use 55 56 axles with a posi you have to cut some of the splined area off whereas 57 axles work with no modification. Other than that I believe they are the same.
Rick

[thehazmatguy]

If you are running a clutch car, I wouldln't spend any time or effort on the stock chevy rear end.

Also, if you have access to the Poncho rear end --> jump on it! If you don't, then please pass it along to me! You'll have less ratio choices because most of the pontiac/olds rear ends saw drag duty, so I *think* ratios start at 4.11 and go into the 5's. I'm not sure if you can get a 3.55 or 3.73 type ratio. I wouldn't be surprised if that's changed though. There's been a lot of new interest in that rear end.

Actually... There's a crazy amount of good info here:
http://www.jalopyjournal.com/forum/s...d.php?t=129676