Packard Forum Index » V-8 (1955-56)

Is there any information available to identify these rear-ends?

Kevin - The only way that I was able to tell on my 56 Exec. was from the 'build sheet' that I got from the Studebaker National Museum. The code was:

Power-Loc Axle (PL), 3.07:1 ratio

I thought that if a car had a 'posi' rear end that when the rear tires were turned by hand (obviously with the car in the air), they both would turn in the same direction. I found that that is not correct, because mine spun in opposite directions and I know that I have the Power-Loc diff. I wish I could be of more help.

my 56 Carib had a brass tag under one of the cover bolts, the tag had "PL" embossed on it, no indication of the ratio (which was 3.54). The carrier was badly worn and I replaced it with a conventional carrier.

So you're saying that the typical test for a "posi" rear end in a GM car where the clutch discs are spring loaded causing both wheels to turn in the same direction does NOT work on a Twin-traction?

The obvious reason I ask is because I just ran this test yesterday on my chopped 56 400 and the wheels turned in opposite directions with the yoke held steady. I guess I should pop the rear cover and look unless someone else has a codification identification.

Craig

My 56 Pat has a "T" tag on the rear end and so does my 400.
packardinfo.com/xoops/html/modules/newbb ... lat&order=ASC&type=&mode=0&start=10
And my wheels turn in the same direction indicating Twin-traction.

page 13 of the rear axle section of the service manual references the metal tag already discussed. service technical bulletin 56T-8 discusses servicing it. Service Counselor vol 30 no 4 describes the differential.

A service bulletin from Packard Philadelphia dated February 21, 1956 says a sticker is attached to the end of the axle shafts for identification, I am sure they survived! SOme early production cars did not get the sticker!


Some where there is a story about dabs of paint on the units.

The color code daubs on the ends of the rear axle are described in one of the TSBs. In short, if you have anything but white or ivory (which may also look yellow), you've got a substandard axle with a history of early failures.

There May be two tags on Twin-Traction rear axles. One is the rear-end gear ratio. The other is a stamped "T" indicating TT. I have never seen the "T" tag referenced in any manual or TSB.

On the clippers which have a dana 44 rear if you remove plug and put your finger into hole it will hit the tt housing . Not sure about senior as they have different axle assembly. I would assume they would be the same.

The Rear Axle section of the 55-56 shop manual - even with the 56th Series Supplement pages - only deals with conventional differential. The tag cited in the shop manual is for axle ratio only, but likely applies to TT as well.

SC Vol. 30, No. 4 (February, 1956) provided "advance info" on the new Twin Traction Differential, including theory of operation and basic service. The reader is referred to STB 56T-8 for additional service details (as exceptions to service for the conventional units).

SSB No. 325, p .3, advises of a brass ID tag, stamped with letter "T", for first design TT (with cone type clutches) as used in all 1957 models. I have to wonder if this tag might have been introduced in later 56th Series production or offered as a retrofit, replacing the aforementioned sticker, but have no documentation to that effect.

In 1958, a third design TT was introduced; SSB No. 339, p. 2, reviews identification by all three tags.

However, I suspect that, as the Packard dealer network evaporated, a lot of these axle tags simply got tossed in the course of service by independent garages.

Daubs of paint (white or red) on flanged axle were applied as identification for engineering conformance - covered in a letter to all dealers on corporate letterhead (not STB). A copy of the 1956 Axle letter (November 2, 1955), was provided to P'Info by Dave Czirr (Owen_Dyneto).