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Is this an "A" type OD?

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Re: Is this an "A" type OD?

Looks like an A-type to me, certainly not a J-type.
 
Re: Is this an "A" type OD?

Looks like it to me too.
 
Re: Is this an "A" type OD?

I have the original gearbox with overdrive on my TR3A. The overdrive shown is just like mine. It shows an "A" type overdrive. The flange around the bell housing with the raised bosses for each bolt shows that it probably came from a TR that was later than the TR3A. If it really came from a TR4, then this gearbox would have all synchromesh gears whereas my TR3A did not have synchro in first.

This would fit a TR3A but you may have to slot the holes about 1/4" holding the rear transmission mount to the frame because the flange of the bell housing is thicker.
 
Re: Is this an "A" type OD?

Actually, the 4-synchro gearbox itself is a bit longer, to accomodate the extra synchro ring. It's not just the flange thickness that causes the rear mounts to move.

Definitely an A-type, definitely a 4-synchro box. Should work fine in a TR3, but as Don notes, you'll need to slot the holes in the rear crossmember (I had to go more like 3/8" to eliminate all force on the mounts). With a 56 TR3 (or TR3A before TS50000), you will also have to massage the transmission tunnel slightly, to clear the starter bulge. Possibly you'll also have to install longer studs in the rear of the engine block, but I don't think so. I did for the late TR6 box I used, but it's even thicker than the TR4.

FWIW, it is possible to rebuild the TR3 top cover with the TR4 shift rails & forks, to retain the dipstick. Or the TR4 top cover will work fine too, you'll just have to use the plug on the side to fill the gearbox or check the level.
 
Re: Is this an "A" type OD?

Thanks gents.
Randall "you will also have to massage the transmission tunnel slightly, to clear the starter bulge." So the later starters are larger and my cockpit tranny cover would need to accomodate the larger bell housing bulge?
You slot the tranny mount itself or oval out the tranny crossmember?
 
Re: Is this an "A" type OD?

At TS50000, with the switch to the exposed starter drive, the bulge in the bellhousing for the starter got significantly longer. Not really visible in the auction photos, but all of the 4-synchro boxes (as well as the later 3-synchro) have the enlarged bulge (even though it was no longer needed on the 6 and 8 cylinder cars). Early cars are notoriously variable, but on TS39781LO, I had to modify the sheet metal transmission cover somewhat with a hammer so it would go over the starter bulge and bolt to the floor without rubbing on the bulge.

The slots go in the crossmember, the frame part that bolts between the rails underneath the rear rubber mount. The mount itself doesn't have enough room to make up the difference.
 
Re: Is this an "A" type OD?

I placed a TR-6 (4 synchro-OD unit in my 59 TR-3A (TS563179) easily with only enlarging the rear engine mount frame holes 3/8 inch to the front and whittling slightly on the spedo cable slot in the floor board. Also moved the shift lever hole aft 2/8 inch and built a 3/8 front piece (which I riveted to the tunnel) so that the hole would be the same diameter.
No problem with the starter clearance.
It gave me a real go with my 4.1 differential.
 
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