Need differential education

[tjc]

where can I learn the difference in (old school positraction), (tru trac), and (limited slip) ? I am at the point in my build that I have to come up with the rear end. The build is a 68 c10 454 bored .030 about 430/450 HP, turbo 400 with a gear vendor OD.

Thanks

[GASoline71]

The only difference is the make of the vehicle they were bolted under.

Chevy = Posi-traction
Chrysler = Sure-grip
Ford = Traction-lock
Olds = Anti-spin
Pontiac = Safe-T-Track
Buick = Positive Traction

All the basic same princinples with a clutch style limited slip differential. Just fancy names depending on manufacturer.

Gary

[truckster]

Actually, the Posi is a clutch-type limited slip and the Tru-Trac is a helical gear locker. Both are types of limited-slip differentials, but they differ in their operation. Then there are true lockers, which lock both axles and will operate even if one wheel is off the ground.

Here's an article from OffRoadExtreme:

http://www.offroadxtreme.com/engine-...ps-with-eaton/

[LongBox]

GM fitted a lot of trucks with a unit they called the Gov-Lock. It does not have a good reputation for durability, so I'd be careful if someone offers you this choice. Some call it the Gov-bomb!

[truckster]

Originally Posted by LongBox

GM fitted a lot of trucks with a unit they called the Gov-Lock. It does not have a good reputation for durability, so I'd be careful if someone offers you this choice. Some call it the Gov-bomb!

Definitely avoid the Gov-Loc. It's a grenade with the pin pulled.

[Choclabnut]

Following...Getting ready to rebuild from scratch, my 12 bolt.
All I have to start with is the housing and the axles!
So I'm also looking for some direction

[garyd1961]

I like the Tru-Trac or Eaton limited slip. As others have said stay away from GM Gov-Loc. I had one to explode on me years ago.

[cdowns]

best way I've found is the factory service manual they tell you all about it how to setitup and keep it working

[Doug's68SS]

Tom in Iowa, looks like you are building my truck, only difference I see is mine has a stroke crank, 489 C.I.. I picked up a used posi out of a 71 I think, and put new gears and bearings. What gears are you going to run with your Gearvendors? I put in 3:73 but am thinking I should of used 4:10. I haven driven it yet as it is not complete.

[davepl]

You (and everyone else) should watch this old video explaining to smart farm kids how a differential works:

https://www.youtube.com/watch?v=yYAw79386WI

It's a great video.

Anyway, there are three main types of limited slip:

- Locker
- Clutchpack
- Helical

Locker is the most positive, but can be a handful if you (for example) floor it and do a trans kickdown while trying the change lanes.

The Helical is what I went with (TrueTrac being a common name). It'll still push, but less so. The only time I really notice it is if I'm coming into a roundabout and accelerate into it, it'll want to push the car straight instead of around the circle.

Clutch Pack (like most GM posis) is the easiest to life with, probably, but wears out eventually and doesn't have the greatest holding power of the bunch.

When I had to made this choice I went Ford 9-inch with a Truetrac differential and am very happy with it.

I also had a Truetrac installed into the Dana60 of my Longhorn. It's a little more aggressive at times, I may not have enough friction modifier in there. But in both cases I'm pretty happy with the result.

If I understand the Detroit Locker, and I'm not sure I do, whe you're going around a turn the outside wheel can go faster, but never slower, than the inside wheel. So there's a minimum wheelspeed that each wheel must maintain, but it can exceed it for going around corner and so on. Sounds ideal on paper. But that article above says of the locker: "the internal components unlock to allow one wheel to spin (free wheel) faster or slower as necessary". That sounds wrong (the slower part) but I'm not 100%

[jeffahart]

Another name, NoSpin differential (detroit locker).

[jeffahart]

Originally Posted by davepl

If I understand the Detroit Locker, and I'm not sure I do, whe you're going around a turn the outside wheel can go faster, but never slower, than the inside wheel. So there's a minimum wheelspeed that each wheel must maintain, but it can exceed it for going around corner and so on. Sounds ideal on paper. But that article above says of the locker: "the internal components unlock to allow one wheel to spin (free wheel) faster or slower as necessary". That sounds wrong (the slower part) but I'm not 100%

Ya the detroit lockers can get pretty funky. I've had several, never went out and bought one. They just came in a lot of my truck rear ends. I keep them. I have one now. They can be a bit unruly. I even had one get out of the diff at a stop light once, it jumped in the cab and slapped me. "Back Fang... heel boy!".... That's a detroit locker They lock, then unlock. But it's the in-between where they get funky. You can make a right hand turn then 100 feet down the road... "SLAM". Unnerving if your not used to it!

[i82much]

Just to add to the confusion, GM made both cone-type (like BOP 8.2) and clutch-type (like the 8.5) limited slip differentials.

Don't forget spools, air and electronic lockers, lunchbox lockers, and something like the TJ rubicon that had limited slip and a selectable locker together.

For a street truck, I'd go with a truetrac myself. I had one in a 2007 Silverado, it was perfect. Great off-road and on. If I had an older truck with a clutch-type posi already in it, I would consider rebuilding the clutches just to save $, rather than having to get the gears set up all over again with a new carrier.

And depending on which rear axle you wind up with, don't forget about things like bolt patterns, brake compatibility, spring perches, available gear ratios, and carrier breaks (e.g., 3 vs. 4 series carriers). As an example, hard to find Dana 60 gears taller than a 3.54.

[tjc]

what would be the ID number or code for a truetrac differential, were the available in 2003 models.

[Bigdav160]

Dodge Ram's used a gear style differential in the AAM 10.5" axle (2003 and newer).

GM used the same axle but used a Eaton gov-loc differential.

I don't think anyone is using a trutrac as OE equipment.

[dmjlambert]

Originally Posted by davepl

https://www.youtube.com/watch?v=yYAw79386WI
It's a great video.

I like that video, thanks for the education. Every time I watch an informative video on youtube, I somehow get sucked into watching at least 2 more videos of people doing asinine stuff such as lighting their own hair on fire or driving crazy as caught on dash cam, or other bad time-wasting stuff. Now I better get out to the truck and turn a wrench to redeem myself.

[BILT4ME]

I had a Gov-Lock on a 12 bolt 1/2T 4x4 with 33" tires. Exploded the diff going around a corner, not getting after it.

Then I installed an Eaton Posi
http://www.eaton.com/Eaton/ProductsS...posi/index.htm

I blew the spiders out of it 4x, but couldn't afford to put in a Detroit Locker. Sold the truck.

Bought a 1970 K2500 GMC. Rear diff was blown out when we bought it. It has a Detroit locker and 4.11 gears. Not gonna have to do it all again.