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TR2/3/3A A type overdrive installation

Gordon_Dedrick

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I am almost ready to install a late TR4 (with the thicker bellhousing) A-type o/d tranny in my 59 TR3A. Planning on getting the extra pieces from Quantum- switch, right angle speedo drive, relay, harnesses, etc. Other than longer bolts for the bellhousing what unknowns am I looking at? Will I need to adjust driveshaft length or is this unit a "bolt in'? Looking forward to having the Laycock unit but don't want any surprises.
Thanks
Gordon
 

TR4nut

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You shouldn't need the right angle speedo drive, the cable can come straight out and is covered by the handbrake boot. I think in going from a non-syncro box to a full syncro box the rear mount holes will be slightly further to the back of the car, so elongating the holes on the mount crossmember will fix it. Drive shaft will be fine - no other modifications needed I think. Teri Ann Wakeman wrote up her experiences here:
https://www.tr3a.info/gearbox_swap.htm
 

Geo Hahn

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Pretty obvious but just in case -- if your '59 is pre-TS50000 then the bulge in the bell housing won't accommodate the original starter. The are a couple of ways around this, some uglier than others.
 

TR4nut

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Pretty obvious but just in case -- if your '59 is pre-TS50000 then the bulge in the bell housing won't accommodate the original starter. The are a couple of ways around this, some uglier than others.

I was thinking it was the other way around? The earlier gearboxes were shallower and couldn't handle the later style starter? But along those lines with a later gearbox potentially you could have a little interference with the gearbox tunnel cover - I seem to recall Randall mentioning that once but I may not have that correct - but I also recall it wasn't that difficult to massage out any interference.
 

charleyf

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You will need an overdrive (longer) speedometer cable.

Charley
 

Marvin Gruber

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Randy,
You beat me to it. I was going to say its the other way around with the starters. You can get by without the angle drive but I recommend using one, you can probably get by with original cable that way and let it lay on top of trans.

marv
 

TR3driver

Great Pumpkin - R.I.P
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But along those lines with a later gearbox potentially you could have a little interference with the gearbox tunnel cover - I seem to recall Randall mentioning that once but I may not have that correct - but I also recall it wasn't that difficult to massage out any interference.
Nope, you got it just right.

Other minor points that I didn't see mentioned:
May need longer studs (the 3 studs at the top of the engine block).
May need to shorten clutch pushrod.

If you do have a pre-TS50000 car, you might want to consider moving the dipstick to the new gearbox.
 
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