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TR4 and TR6 Overdrives Whats the diffeance?

To: triumphs@autox.team.net
Subject: TR4 and TR6 Overdrives Whats the diffeance?
From: Jim Hill <Jim_Hill@chsra.wisc.edu>
Date: Fri, 2 Apr 1999 12:27:01 -0600

Jeff Slaton wrote:

> I had a question about my OD tranny.  I have purchased a TR2 within the
> past year and it came with an overdrive.   I noticed that when I got a
> little closer look at the car the engine and OD tranny are out of a
> TR4.  How much differance is there in that OD tranny and an OD in that
> would go in my TR6?  Would it work in my TR6?  Is it an A type?  Will an
> A type go in a my 74 TR6..

Ken Nuelle wrote

> I believe that the TR4 OD tranny will not fit in your '74 TR6. The rear 
> mounts are different. You need a J type for the '74.
> Since you won't be needing the A type tranny, let me know when you plan to

> throw it out so I can be there to catch it!

Irv Korey wrote:

> Not so. The rear mount of the A type and the rear mount of the non o/d
> tranny from a 74 are identical. If your 74 originally came with a J type,
> you will have problems making the A type fit. Otherwise, it goes right in.

Philip Schulert wrote:

>   The rear transmission mount was changed in 73 so I do not think short of
> cutting and welding an Atype overdrive will go in a 74 TR6

You need an J-type OD for your `74 TR6 only if you want to have the unit
that's the correct original equipment for the car.

Since the transmission came mounted to a TR4 engine, one would presume that
it's an A-type. But since the whole power train came to you wrapped in a
TR2, who knows? If you can describe the OD unit and which way the actuator
is mounted, it's not hard to identify visually - or you could look it up in
the TRF catalog or one of the TR6 manuals (which should show both types).

I'm sure that Irv is right about the rear mount of the A type and the rear
mount of a `74 non OD trans being identical. But even if that doesn't apply
to your car, you ought to be able to buy any of the different rear mounts.
The worst possible scenario, such as if your `74 TR6 originally came with a
J-type OD and you want to replace it with an A-type, would involve a new
transmission rear mount and possibly having to snip some small notches in
the floors around the mount. Welding shouldn't be required.

Jim Hill
Madison WI

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