PDA

View Full Version : Is a stock differential really "that" fragile?



Geoff
06-28-2013, 10:25 AM
Is a stock '55 differential really "that" fragile?

Back in the 70's my uncle ran a 4:88 geared sock rear with an early posi unit in a 55 BelAir post.
He ran cheater slicks, a 4 speed, 12.5:1 .060 over 350. He ran mid 12's and says he never broke
anything in the rear end.

I am wanting to run a warmed over LS1 in my cruiser. It won't have wide tires and will have a
4L60e. Am I really in danger of destroying the stock open 3:55 rear?
I realize I won't have a posi, but do I really need to worry?

chevynut
06-28-2013, 11:26 AM
IMO as long as you're not racing, you will be fine. There are thousands of these on the road. I had one behind a 427 in my 55 Chevy, and never had a problem with it. I smoked the tires once in a while too. Us rodders always want the "best" even when it's not needed.

What's the worst that could happen? You break it and have to fix it?

NCW
06-28-2013, 11:34 AM
Is a stock '55 differential really "that" fragile?I realize I won't have a posi, but do I really need to worry?

Noop! .................................

Rick_L
06-28-2013, 05:38 PM
To me the stock rear is okay for "every day" driving. But in my opinion, it has to be described as somewhat fragile if you drive any harder than that.

The #1 weak spot is the spider gears in an open differential. You can break spider gears in an open differential even with street tires and an automatic. On the other hand, a posi unit will just about eliminate that problem.

The next weak spot is the axle shaft. IMO you probably won't have a problem on street tires but definitely would with slicks, even street radials.

The wild card is the bearing cap. I broke one with street tires and an open differential. Never did again, even with racing with slicks and a 4 speed.

Maddog
06-28-2013, 06:03 PM
If you want to bullet proof it, within reason do install a good posi, use this guys bearing caps: http://www.bruneauperformance.ca/camshaftspringsrockers.html Buy new, good alloy axels , Dutchman's are good, and don't forget good quality spicer U joints

chevynut
06-28-2013, 06:20 PM
Yes, mine was a posi. I guess that's why it held up to the 427.

Bihili
06-29-2013, 06:20 AM
Is a stock '55 differential really "that" fragile?

Back in the 70's my uncle ran a 4:88 geared sock rear with an early posi unit in a 55 BelAir post.
He ran cheater slicks, a 4 speed, 12.5:1 .060 over 350. He ran mid 12's and says he never broke
anything in the rear end.

I am wanting to run a warmed over LS1 in my cruiser. It won't have wide tires and will have a
4L60e. Am I really in danger of destroying the stock open 3:55 rear?
I realize I won't have a posi, but do I really need to worry?

http://www.tomsdifferentials.com/tomp.htm

OLKY55
06-29-2013, 03:44 PM
Back in the 70's, my stock rear was stronger then my driveshaft and my T-10 trans.

solidaxel
07-07-2013, 04:07 PM
I did experience a "bit" of trouble with my 62 409 dual quad 4 speed when I changed rear gears. I found the spiders to be the weak link in the non posi rears, but the posi did seem to take MUCH more abuse. remember that the biggest tires for the street tires were 820-15 Burcrons and cheater slicks. You have much more selection and width of tires today so you may have some trouble!!

55mike
07-08-2013, 07:13 PM
I've heard it said " a drag racer can break a bowling ball in a sandbox.." This said, I believe with an automatic and some prudence you will be fine.

the_dawg
08-01-2013, 08:59 PM
Some good links here. I think ill do some axle work too

warren57
08-01-2013, 09:47 PM
Well all I can say is.... they held up pretty well when we were in high school and believe me, we didn't baby them. I ruined many transmissions and u joints, but never a rear. But remember tires weren't all that great then, bias ply and in the 60's the new and improved "wide ovals" with had little or no traction! In the 50's polyester tires were new technology over nylon. Not to mention, we never had any tread, we always ran around on bald tires, couldn't afford anything but used tires (ha ha) Nothing like the traction available today from radials.