Mt75 Gearbox In A 3A

[rthomas69]

I've been offered an MT75 gearbox (from a Sierra dohc) to go with a high spec 2.1 pinto I'm getting but will it actually fit in my 3A as I know it's a larger casing than the type 9? It does seem an obvious upgrade as my type 9 is only a 4 speed which was mated to a standard 1.8 pinto.

Rich

[Snapperpaul]

What diff are you running?

MT75 ratios are generally shorter and need a 3.6 diff or better

[tractor]

you will be needing a new propshaft aswell

[cb750]

Have you actually got a type 9 fitted? Aren't all type 9s 5 speed?

[tractor]

no the old type nines were four speed I think they were called rocket boxes but I may be wrong

[rthomas69]

After a bit of digging I believe my diff is a 3.62 & yes it is a 4 speed type 9. So based on that I'm guessing the diff would be ok? As for the propshaft are they different splines or length or both? And the other question is whether an MT75 would physically fit in the tunnel? Or am I just better off keeping the set up I have & just do a direct replacement (2.1 pinto replacing the 1.?

[tractor]

if I can remember it is different splines and the mt75 does not leak oil when prop removed and a type 9 does so the input of the drive shaft may be different aswell

[rthomas69]

Sounds like I'm better off keeping the box I have for now

[tractor]

unclecheif was running a 4speed box and he was very happy with it only changed to an mt75 cos he upgraded to a zetec

[cb750]

It doesn't really matter but Burton Power say the 4 speed sierra box is the type E. When it went to 5 speed it then became the type 9. Yes Tractor, they are called rocket boxes but the rocket term should refer to the competition 4 speed versions. Am I wrong but doesn't the MT75 box have a flanged output for the propshaft?

[Guest Ian & Carole]

It doesn't really matter but Burton Power say the 4 speed sierra box is the type E. When it went to 5 speed it then became the type 9. Yes Tractor, they are called rocket boxes but the rocket term should refer to the competition 4 speed versions. Am I wrong but doesn't the MT75 box have a flanged output for the propshaft?

 

Correct. 4 is E rocket was a comp version of the E

[keith kelly]

Mt75 is flanged so new prop will be needed. Even if you changed to a five speed type nine you would need a different prop as the 4 Speed is splined different. Gbs do my75 prop for zero not sure if it fits a 3a but it is sleeved. I have seen my75 in 2b but have no idea on yours. Type9 would be an easier mod

[theduck]

Believe MT75 too wide for mono's

[rthomas69]

Thanks for all the replies, bottom line is that I'm staying with the current box which does leave me more money for other goodies now :-)

[Longboarder]

Sierras came with type 3 box (20 spline prop 1.3 and some 1.6 models), type E box (23 spline prop some 1.6 and some 2.0 models) and type 9 box (some 1.6, 1.8, 2.0 models) and then mt75s.

You could have a type 3 or E. Both are shorter than the type 9 and have a mount forward of the position that a type nine mounts but different spline sizes.

 

Nigel