want to fit overdrive - what type?

[badhuis]

I am a bit confused about overdrives.

What is the physical difference between an A type and a J type? I believe the J type needs another rear mount, can this be achieved in the TR4?

Are the input shafts the same - do they both accept the standard clutch?

Is another propshaft needed?

Can a overdrive unit be fitted to the back of a normal gearbox or are adaption plates or parts necessary?

Any pros and cons between the two types?

Tips for getting one?

 

Any info much appreciated.

[Ade-TR4]

Hi

For the TR4 you're best going for the A-type O/D.

The J-type can be made to fit, but the chassis bracketry is a bit cobbled-together.

A genuine A-type box will add value to the car too.

TR4 O/D has a "harsh" engagement, the TR4a had a "softer" engagment.

You can convert non-O/D to O/D, and adapter plate is required and a different (main - I think) shaft.

You can use other 'boxes, but some the input shaft lengths may not be compatible.

Propshaft is the same as is the clutch etc

On a standard/ mildly tuned car, stick with an A-Type (O/D on 2nd, 3rd and 4th!)

It's a great upgrade, what ever you choose!

Ade (and my 7-speed car!!!)

Edited September 21, 2010 by Ade-TR4

[vivdownunder]

The correct A Type overdrives for the TR4 are -

 

22/61374 earlier TR4

22/61712 late TR4

22/61753 TR4A (with softer engagement for IRS)

 

All will fit on a TR4 gearbox if they have the original correct adaptor plate.

 

The hard part to find is an overdrive mainshaft for the gearbox.

 

You also need the 2 x isolator switches for the top of the gearbox, O/D supplementary wiring loom, O/D relay and a column stalk O/D switch.

 

There is no change to the input shaft or clutch, but it's wise to check the clutch for wear while the gearbox is out for the conversion.

 

The same propshaft is kept, but inspect and replace the uni joints if they are suspect. Re-grease the propshaft spline too.

 

You can fit a late TR6 J Type O/D, but a mount has to be fabricated. Moss sells an adaptor mount, but reports are that it isn't ideal.

 

Tips for getting an O/D - Forum "wanted to buy" is a good start. Do a thread search for professional O/D suppliers/repairers.

 

Regards,

 

Viv.

[Norfolkjohn]

badhuis,

 

Don't know where you are located but there were a couple of O/D specialists at the International in Malvern. Both are based in the midlands of the UK

 

Overdrive Repair Services are in Sheffield

 

http://www.overdrive-repairs.co.uk/index.html

 

O/D Spares are in Rugby

 

http://www.odspares.com/

 

I suspect either organsiation could give you further advice.

 

As others have said I would go with the A Type O/D as orignially available as an option on the TR4 / 4A

Edited September 22, 2010 by Norfolkjohn

[Ian Vincent]

 

The hard part to find is an overdrive mainshaft for the gearbox.

 

 

 

 

I believe that Overdrive Repair Services in Sheffield will re-manufacture an overdrive mainshaft for you using your original non overdrive shaft. I don't know how much is costs.

 

I had them rebuild a saloon O/D for me and convert it to a TR O/D - the cost was very reasonable considering that it included a new rear housing and upgrading all the springs and other bits inside to TR spec. It came back looking like a new unit.

 

Rgds Ian