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TR2/3/3A Clutch for gearbox swap

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Konrod

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I'm working through my TR3A, and next in the list is to swap the 3 synchro 4 speed for a 4 synchro OD box, and having read up the only issue seems to be the length of the studs/bolts at the bellhouisng flange (possibly, depending on the donor box) and slotting the gearbox mount.

One thing I can't find a definitiev anmswer to is the clutch. Can I still use the TR3 clutch/plate or do I need the concentric spring TR4 items? Hope not as I guess that means changes to the flywheel, at which point I feel a slippery slope coming wallet wise.............

Thanks

John
 
Yes, the TR3 clutch will work fine. You may need to make some changes at the slave cylinder, though (which would be true for either clutch).

In my case, I made up a shorter pushrod, and a little tab to keep the return spring the same length. But I think that pounding the edge of the clutch cover flat, and switching to the TR6 style slave mounting would work without having to change the pushrod.
 
Great, thanks for the reply. I can make any mods as I need to, it's just whether I need to plan bigger changes, as I want to get this done over a weekend.

Regards

John
 
Take a look at where the speedo cable goes through the side of the gearbox tunnel. The 4 synchro box moves the connection point just a little.

On my 3A, I just added a piece of old fuel line to protect the outer cable from rubbing on the edge. But on my current TR3, I had to trim away a bit of the opening to give it room.
 
You do not mention what commission number your TR3A has. If prior to TS50000 the bulge on the TR4 bellhousing may be bigger than what you have now and require some massaging of the tunnel cover.

Edit - never mind, found an old post where you mention it is a 1960.
 
If you are going to use a TR6 box and OD and you havent fitted the front pannel yet, slotting the front engine mounts to move the engine forward about a 1/4 inch will make the fit a lot more comfortable . The bell housing flange on the 6 box is a lot thicker than the 3 or 4 box and to get it all to fit will take the slots on the gearbox mount almost to the limit

Graham
 
I'm not sure I follow you, Graham. I had plenty of room to slot the holes in the rear crossmember (after bending down the tab). And moving the engine forward is likely to cause clearance problems with the radiator. Don't forget that the engine rocks forwards on it's mounts during a hard stop.

Also, it's not the flange thickness that causes the mount to be farther back. The same difference exists with the TR4 gearbox, which still has the thin flange. It was the addition of synchomesh on 1st gear that made the main gearbox get slightly longer.
 
Thank you Randall for clarifying that for me, its amazing how you can look at something a thousand times and not see the obvious. Just because the flange is thicker doesn't make the box longer,the extra metal is behind the face not in front of it.

Graham
 
Thought I'd give you an update. I have done the gearbox swap - twice! The original came out sweet as a nut, getting the new box in was a pig, but once we had everything lined up it slid in and we could bolt it all up. I found a very useful garage tool in the process, a slim 21 year old son who can slide under the car and wiggle the bellhousing :smile:

Once everything was in place and I'd wired up the overdrive it was time to test it. First depression of the clutch caused an almighty grinding, clearly the release bearing. So, it all had to be disassembled again. the release bearing was rubbish - found out since there was a faulty batch, my supplier has 10 on the shelf, all with the same manufacturing fault, and no, it wasn't a cheap Chinese job.

So, all put back together, cursing the gearbox to exhaust mount and my fat fingers for a second time. This time it all worked. The first swap took three evenings, the second time about 4 hours!

In the process, removing the starter motor, we broke one of the tangs from the brake light switch:rolleye: As I'm up against time (and accessing it means taking the exhaust off again....) I offer you bodge of the week, which is actually very solid and may remain for some time........

Cheers

J
 

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That slim 21 year old is the right accessory to fit a TR gearbox, a job you only want to do once?

Graham
 
Konrod said:
...we broke one of the tangs from the brake light switch:rolleye: As I'm up against time (and accessing it means taking the exhaust off again....
Click to expand...

A mechanical brake lamp switch is a reasonable alternative for reliability but... I have always been able to easily access the pressure switch by removing the right front road wheel - then it is right there in front of you. But perhaps RHD cars differ in this regard.
 
Like the bodge. May have to do something similar if my pressure switch does not work.

Are Overdrive gearboxes easy to come by in the UK?

David
 
Hi David, its like getting a Scotsman to part with money - it's gone past the point where cars are being broken up and you can find them in scrapyards. There are a couple of specialists who rebuild them, and they can build new ones (and I mean completely re-manufactured) from parts provided you have an exchange unit, I had to do a three cornered deal to get mine offering a saloon gearbox with a J type overdrive in exchange. Cost me a lot of money, but the cars value goes up more as everyone knows how hard they are to get.

The odd part is the three synchro box I took out has an O/D switch on 3rd/4th with the wires cut off (but no O/D unit), and an OD switch already on the dash. Almost looks like it used to have O/D but it go swapped for some reason
 
Konrod said:
The odd part is the three synchro box I took out has an O/D switch on 3rd/4th with the wires cut off (but no O/D unit), and an OD switch already on the dash. Almost looks like it used to have O/D but it go swapped for some reason
Click to expand...
I've done that a few times myself : Buy an entire car to get the OD, rob the OD, sell the car without it.
 
Much as I thought. Would be nice to get one. Have to keep looking and save my pennies.

Makes me sad to think I sent one to the breakers yard with an OD box. Was rear ended and the car was already rotten to the point the frame outriggers were gone on one side.

David
 
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