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TR2/3/3A Transmission Installation Problem TR 3A

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DornTRoriginal

DornTRoriginal

Jedi Hopeful
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I’d appreciate any insight anyone has about a problem I’m having with the drive train installation on my TR3:

I am trying to install the (new to this 1959 TR3A, rebuilt by others) transmission with an overdrive onto the chassis or my 1959 TR3, but the rear bracket (with a new slientbloc mounting) is not matching up correctly to the original bracket welded onto the frame (see the picture) I have rebuilt the motor and installed a new pressure plate, clutch and refaced the fly wheel. As you can see the rear bracket is not matching up to the bolt holes, it’s off by about a half of an inch. The rear support is welded to the car chassis and the bracket fit the old transmission nicely so why is this not fitting better with this new OD transmission? Are these transmissions dimensionally different (best I can tell they are very close)? I could force the transmission assembly into position so that I could get the bolts installed, but I would need to use a lot of muscle and a large pry bar, this doesn’t seem the right way to go. Another option I thought of is to relocate the bracket by re-welding the existing bracket or creating a new support welded onto the frame so it all sits well as is? However, if I do this I am wondering if this will require me to alter the cover to accomodate the shifting mech. I thought this was going to be the easy step of the day......
:playful:
Transmission Installation problem (02) email.JPG

Transmission Installation problem (1) email.jpg
 
Aloha Dorn,

ISTR that boxes with syncro first (TR4 & up) are about 1/2 inch longer to accommodate the first-gear syncro ring. I couldn't tell from the pix what type you're fitting.

Jeff
 
Right, I believe I've read that you need to elongate the mounting holes for the rear transmission mount bracket to accommodate the all-synchro transmission. Is there only one cut-out switch on the transmission selector cap versus the 2 that I would expect?

Scott
 
I agree - slot or redrill the two holes for the transmission mount and you'll be fine.
 
I've drilled the crossmember on several cars now, seems to work out well and doesn't require any welding. You may have to bend down the flange at the back of the crossmember, though.

I can't see how thick the flange is in the area where the clutch slave mounts. I have a later TR6 box in my TR3, and the thicker flange required shortening the pushrod, plus adding a little tab for the return spring.
 
Mahalo Brah, it is a TR4 A type OD it appears that I need to make a bigger puka for da bugger......
 
Thanks for the help, there's not enough metal to "elongate" the hole particularly in the back, I think I can make a new plate either by drilling a hole into the original plate and adding a new cross piece. I am disappointed that I can't use the original bracket as it is so "nice" and a good fit.....

I do not have the tunnel cover so will I need to modify it too? I am thinking I will need to adjust it too. One other question is do I need to replace the cap where the gear shift lever attaches to the top of the gear box or is my original one for the TR3 non OD the same for the new TR4A all syncro unit?
Transmission rear plate email lg.JPG
 
DornTRoriginal said:
Thanks for the help, there's not enough metal to "elongate" the hole particularly in the back, I think I can make a new plate either by drilling a hole into the original plate and adding a new cross piece. I am disappointed that I can't use the original bracket as it is so "nice" and a good fit.....

I do not have the tunnel cover so will I need to modify it too? I am thinking I will need to adjust it too. One other question is do I need to replace the cap where the gear shift lever attaches to the top of the gear box or is my original one for the TR3 non OD the same for the new TR4A all syncro unit?
View attachment 27858
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The holes you show are not the ones that get modified.The holes for the trans mount to that plate are the ones.I welded up the old holes,but if you drill new ones(2) just touching the old ones its about right .As Randall mentioned I needed to also bend the back upright flange on the rear of mount back or it hits the trans.Tom
 
Alright, I got it... much more better way! Thanks!
 
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