Let's Talk Differentials

by Psychlonic Thu Jan 06, 2011 10:23 pm

Finding information online regarding differentials is rather sketchy, to say the least. First, let's get what I'm looking for out of the way:

I'm looking for "the right" differential for my Malibu. Said car will be primarily a street car with a little messing around on the strip, but I also want to be able to handle corners as best as possible. So the primary importance of the differential is for cornering performance, but I will not complain if it also helps me launch better. Reliability is a concern of course, and I don't really care one way or another about gear whine - whining would be neat but it's not really a factor here.

Now then, looking up everything from good ol' positraction to Detroit lockers has been very confusing and contradicting online. I'm not sure what I'm wanting to get, here. I've read that both can cause PROBLEMS with cornering... is this true and why? I've read that both can effect winter and rain performance - I am willing to accept that.

I'm pretty much at square one, here.

by dragons_lair59 Fri Jan 07, 2011 12:34 am

you want to up grade axles and ad c clip eliminators for reliablity then i sugest a true lock it is an auto locking diff that locks for lauches unlocks for cornering and has no clutches or springs to go bad just my opinion

by Psychlonic Fri Jan 07, 2011 7:27 am

Ok so reading more about this, you're probably right and it sounds like the Detroit locker is probably for me. I do have a question about this, though. It seems that the locking action is mostly dependent on hitting the gas hard, is there a potential for disaster when giving it gas through a corner? What should I know about taking corners with a locker that could suddenly lock or unlock mid-corner?

by JB2wheeler Fri Jan 07, 2011 7:33 am

There is nothing wrong with just a factory rear with positraction for your purposes, but for a little better option, go by the previous post. Mostly what you want to concentrate on is your suspention. You need better upper and lower control arms in the rear and a set of sway bars front and rear. . JB

by The Dude Fri Jan 07, 2011 10:46 am

dragons_lair59 wrote:you want to up grade axles and ad c clip eliminators for reliablity then i sugest a true lock it is an auto locking diff that locks for lauches unlocks for cornering and has no clutches or springs to go bad just my opinion

If you get real lucky, your car might not even have C-clips. I've heard of a few Chevelles getting BOP 10 bolts since all 73-77 cars had the 8.5 ring gear 10 bolt. That's the only difference in later model cars is that Buick, Olds, & Pontiac mostly had bolt on axles where as Chevy had C-clips. Again, some Chevelles did have the bolt on axles probably due to a shortage of C-clip axles, but who knows? I'm almost positive that I remember having bolt on axles under my 73 Chevelle.

If you are really concerned about the locker ratcheting then go mini spool or Lincoln Lock it. FWIW though, I don't see why you don't just get a limited slip unit instead of a locker. For what you described it would be what you want to go with.

by JB2wheeler Fri Jan 07, 2011 11:40 am

My 74 Elky came from the factory with BOP rear. I ordered Moser axles for it thru a speed shop and told them BOP and Moser sent Chevy and they had to be sent back. JB

by 74Malibu383 Fri Jan 07, 2011 11:47 am

I'm still running the stock 8.5" 10-Bolt with the strongest Eaton Posi unit they make. I believe there are three different spring rates associated with the Eaton units. Get the strongest one, throw one of those aluminum covers on for support and smash that gas pedal. Knock on wood, I haven't had any problems with it, and have put it through a ton of abuse. He!!, I’m even using the factory axles.

I do second JB’s comment on upgrading the upper and lower trailing arms though. It definitely made a big difference on mine.

by Psychlonic Fri Jan 07, 2011 12:16 pm

Suspension is definitely on the to-do list, but I think I have more of an idea where to go with that. I'm just really boggled about the various differentials out there. I haven't driven enough vehicles to really KNOW what they are all about and what they drive like. Maybe I should run around and start asking if I can borrow keys? Very Happy

I guess we'll see when the time comes to put down money where I want to go. If I've got enough, I'm thinking I still want to go with the locker after beating information into my skull all night. But just curious 74Malibu383, would you say you're generally happy with your Posi? Anything significantly good or bad to say about it?

Thanks for all the responses so far guys, I appreciate it.

by JB2wheeler Fri Jan 07, 2011 12:29 pm

There is a guy in Europe somewhere who has a 73/77 Chevelle and lives near a fancy well known road course and he runs his car on the track all the time for kicks. He has a bunch of youtube videos up and it sure looks like great fun. I do not have the links for the Youtube, maybe I will run across them later today. JB

by BlackChevelleSS Fri Jan 07, 2011 1:29 pm

I personally do not like automatic locking diffs. I hate when it locks when I dont need it and doesnt lock when I do. (Have those pos gov locs in the chevy trucks) I love my factory eaton posi, ive added shims and tightened up the springs, and ive never had an issue of one wheel peel with launch and going around corners youd never know it was back there untill to power slide it, which is all in good fun.

Yes the 73 that rago had was bolt in axle.

by 74Malibu383 Fri Jan 07, 2011 2:12 pm

Psychlonic wrote:Suspension is definitely on the to-do list, but I think I have more of an idea where to go with that. I'm just really boggled about the various differentials out there. I haven't driven enough vehicles to really KNOW what they are all about and what they drive like. Maybe I should run around and start asking if I can borrow keys?

I guess we'll see when the time comes to put down money where I want to go. If I've got enough, I'm thinking I still want to go with the locker after beating information into my skull all night. But just curious 74Malibu383, would you say you're generally happy with your Posi? Anything significantly good or bad to say about it?

Thanks for all the responses so far guys, I appreciate it.

Yes, I am very happy with it. It drives the same no matter what the conditions. It really helps to know how a car is going to react before smashing the gas. If it's always a surprise, it's not worth it.

by bigredlaguna Fri Jan 07, 2011 9:27 pm

So what do I have here then? I bought this a while ago and was told it was an Auburn differential. After getting it, I couldn't find any info about it, like what gear lube to use, torque specs, etc.

Let's Talk Differentials Img_4510

by BlackChevelleSS Sat Jan 08, 2011 4:16 am

I would count the splines on that and make sure its not a 30 spline. otherwise as I can tell its a late model (truck? or caprice) eaton posi. its a good unit ive got a couple on the shelf

by bigredlaguna Sat Jan 08, 2011 4:04 pm

The guy sold the axles to me also, I think they are Moser axles. He had wanted to use it in a previous gen a-body but his was an 8.2 instead of an 8.5.

by dragons_lair59 Sat Jan 08, 2011 9:11 pm

this is what im talking about
http://www.summitracing.com/parts/PWT-1920-LR/

by Limey SE Sat Jan 08, 2011 9:44 pm

JB2wheeler wrote:There is a guy in Europe somewhere who has a 73/77 Chevelle and lives near a fancy well known road course and he runs his car on the track all the time for kicks. He has a bunch of youtube videos up and it sure looks like great fun. I do not have the links for the Youtube, maybe I will run across them later today. JB

Here you go JB his name is Blazerteam and is a member here as well He is in Norway

by Psychlonic Sun Jan 09, 2011 8:49 pm

That is badass!!!

by 74Malibu383 Mon Jan 10, 2011 11:47 am

bigredlaguna wrote:So what do I have here then? I bought this a while ago and was told it was an Auburn differential. After getting it, I couldn't find any info about it, like what gear lube to use, torque specs, etc.

Personally, I would stay away from Auburn Diff's. I blew up two of them when I was only putting out half the HP I have now.

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