A or J type overdrive unit

[lofty]

Hi all,

Anyone know the difference between an 'A' type and 'J' type overdrive unit?

Not sure if the pictures help.

The Stag is a 1973 (January 8th) Mk II ? with manual gearbox and original 3.0L engine.

Thanks

Dave

[Coppo]

Hi Lofty.

You have an A type overdive.

Coppo.

[maverick]

Hi Lofty.

You have an A type overdive.

Coppo.

Coppo,
Hi Can you tell me how to spot the difference?
Mine is a 71 MK1 mod,but had reconditioned gearbox
Thanks Mark

[DJT]

Coppo,
Hi Can you tell me how to spot the difference?
Mine is a 71 MK1 mod,but had reconditioned gearbox
Thanks Mark

Different castings and solenoid. See pictures for help:

A Type:

A Type.jpg

J Type:
J Type.jpg

Neither of these are on Stag gearboxes, but they will help identify what you have.

Dave

[Bandit1200]

Mine's a J type and it's not the same as yours.

Jtype has a finned bottom plate.

Steve

[Stagdad]

Coppo,
Hi Can you tell me how to spot the difference?
Mine is a 71 MK1 mod,but had reconditioned gearbox
Thanks Mark

This is a J type from a similar angle nicki minaj 003.jpg
Cheers Steve

[Coppo]

Coppo,
Hi Can you tell me how to spot the difference?
Mine is a 71 MK1 mod,but had reconditioned gearbox
Thanks Mark

Hi Mark.

The soleniods are an easy spot... A type is at an angle, J type is straight......



A easy way is the sumps where the filters are, A type is a round brass cover, J type is a rectangled cover.

Hope this helps.

Coppo.

[jleyton]

Everything you want to know about Overdrives is here:http://www.buckeyetriumphs.org/technical/technical.htm

Although this site is primarily for TRs, quite a bit of the info, including Overdrives, is equally applicable to Stags.

Cheers

Julian

[Westfaling]

As I recall from overdrives past the A type engages with more of a satisfying surge but if trying to change gear with it engaged (3-4) it crunches. The J type doesn't crunch. But I've also got a LH type in my MGB so I could be mistaken.
Nick

[Mike Stevens]

'Tis true - the 'A' type keeps the oil pressure up all the time and then diverts it to the operating pistons when wanted - hence a faster engagement. The 'J' type keeps no pressure and only builds it up when wanted - hence slightly slower engagement. It also sometimes seems to have a delayed dis-engagement too, I guess for the same reason.

'J' type has a slightly higher ratio too....

Cheers,
Mike.

[PaterB]

Can i cross-fit a J type on a Stag formerly equipped with a A-Type or is there much adaption work needed?

[DJT]

Different main shaft in the gearbox. So it either requires the equivalent 'box or a rebuild.

Dave