Rear Axle: TT how can you tell

[TXmark]

I know there is a way to tell by turning one wheel when it is up on blocks. Is there also some identification on the unit

[voxnut]

From Bob's website:

If you find a tag on the cover plate with 45B, this will tell you it is a limited slip (Twin Traction) rear end (not a 45 axle). Early Twin Traction Axles used a axle cover tag with a large T on them (they
had a 30 degree ramp angle).

A 45 "C" is a Dana 44 with the Limited Slip. A Limited Slip differential is denoted as a "45" and the "C" is the type of Limited Slip" clutch assembly.If you look in your Studebaker shop manual it shows the different clutch packs and their letter designation.


Tags also were on the axle cover plate, with the rear end ratio listed.

Axle model #'s are cast on the housing, just around the corner from the filler plug. Spray some engine gunk on the axle and take it to a self service pressure car wash to clean it up.

[JWL4541]

As I recall, with both rear wheels off of the ground they will turn in the same direction in a limited slip differential (Twin Traction). In a conventional differential, the wheels will turn in different directions.

(o[]o)

[swvalcon]

If the car runs just get it on a hard surface and gun it enough to spin the tires. Not only will that tell you if it's twin traction it will also tell you if it works.

[StudeRich]

Be careful to not misunderstand this one:

From Bob's website:/Cut/
Axle model #'s are cast on the housing, just around the corner from the filler plug. Spray some engine gunk on the axle and take it to a self service pressure car wash to clean it up.

The Dana Model Number is raised on the Diff. housing on the Web between the "pumpkin" and the Right Axle Tube, usually to the rear, but a few are on the front side.
This will ONLY tell you if it is a 23, 27 or 44 though, as a 45C (TT) or whatever Alpha, is NOT noted there.

The "Other" method to tell a Standard Open rear end from a TT is, just pull the Fill Plug and put your finger in there, if you feel the Twin Traction Case very close to the Cover it's a TT.

[Mike Van Veghten]

Only ONE way to be 100% convinced...remove the housing cover and look.
Every other way can be off, in one way or another.

I've seen loose posi unites and very tight open carriers...they can fool you.

Mike

Plus, that provides a great excuse for changing the axle oil, which very few people ever do..!

[TWChamp]

I've worked on GM cars with posi-traction, but never had the Studebaker Twin Traction apart. Are they different?

[StudeRich]

I've worked on GM cars with posi-traction, but never had the Studebaker Twin Traction apart. Are they different?

Yes, these are Dana Units like in Jeeps, not like the "Johnny come lately", GM made Positractions.

[Play Wagon]

Since it's been brought up: the rear end of my '59 Lark wagon (currently out of the vehicle) is a 44 TT unit. I was surprised when, with the pinion yoke held stationary, turning one axle made the other rotate the opposite direction- I thought that was characteristic of an open differential. Does that suggest worn clutches or...? It's got about 120k miles on it, yet the teeth all look clean & sharp w/barely any detectable (and quite fine) shavings in evidence. Thanks for any input you might have...
JSC

[TWChamp]

Since it's been brought up: the rear end of my '59 Lark wagon (currently out of the vehicle) is a 44 TT unit. I was surprised when, with the pinion yoke held stationary, turning one axle made the other rotate the opposite direction- I thought that was characteristic of an open differential. Does that suggest worn clutches or...? It's got about 120k miles on it, yet the teeth all look clean & sharp w/barely any detectable (and quite fine) shavings in evidence. Thanks for any input you might have...
JSC

I'd check the spring pressure and clutches for wear. We always added special lube for posi-traction units when I worked at the dealership. I wonder if your rear has the correct gear oil?

When I asked if the GM posi was different, than the Twin Traction, I was wondering if the TT used clutches and springs or some other method to lock the axle?
Years ago I read an article about a locking rear end that used worm gears and no clutches, but I don't know if it ever got into production, or only as far as the design table.

[Studebakercenteroforegon]

Years ago I was crewing on a '71 Ford Torino Super Stock oval track (asphalt) car. We kept on breaking right side axles so we bought a quick change with floater axles. It had a TrueTrac differential which did have worm gears as part of its design.

[bezhawk]

I'd check the spring pressure and clutches for wear. We always added special lube for posi-traction units when I worked at the dealership. I wonder if your rear has the correct gear oil?

When I asked if the GM posi was different, than the Twin Traction, I was wondering if the TT used clutches and springs or some other method to lock the axle?
Years ago I read an article about a locking rear end that used worm gears and no clutches, but I don't know if it ever got into production, or only as far as the design table.

The Torsen posi is the best available,and has been used by various manufacturers, as well as after-market.
The Stude twin traction uses a tapered ramp on the spider gear cross pins to load the clutches. The alternating clutches are slightly conical to engage more smoothly. The easiest way to tell if you have a twin traction is by removing the filler plug, and sticking your finger into the hole. An open carrier will be hard to touch as it doesn't fill the case well. The twin traction is larger, and you won't be able to stick your finger past the first knuckle.