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Stupid question Does anyone know how much an Imp transaxle could take?
AdrianH - 19/8/12 at 08:15 AM

There are a few imp gearboxes on the bay and I was just wondering what the old 4 speed boxes could take.

Adrian

ashg - 19/8/12 at 08:41 AM

anything over 100hp will make it pretty much explode

britishtrident - 19/8/12 at 08:45 AM

Standard Imp boxes no a lot, JK 4 speed straight cut boxes are limited by the stiffness and strength of the casing (especially for off tarmac use) I have seen one bolted to a Clubmans spec 1600 xflo for circuit use. But beyond that ?!

britishtrident - 19/8/12 at 09:29 AM

quote:
Originally posted by ashg
anything over 100hp will make it pretty much explode


A full race 998 Imp would turn out over 120 at the flywheel, even the works race spec R22 or R23 cammed 1.4 engines turned out about 120 and really really good Chessman or Carter ones with fancy heads and cams were over 130 some of the bored stroked ones over 140.

ashg - 19/8/12 at 09:39 AM

yes true but those guys are usually rebuilding the boxes to take it. your typical ebay second hand offering wont

also adrian how are you planning to use it. in the imp the box is under the rear seats with the engine behind. if you plan to turn it round and use it in the orientation most race cars use you will have 4 reverse gears.

[Edited on 19/8/2012 by ashg]

AdrianH - 19/8/12 at 11:17 AM

quote:
Originally posted by ashg

also adrian how are you planning to use it. in the imp the box is under the rear seats with the engine behind. if you plan to turn it round and use it in the orientation most race cars use you will have 4 reverse gears.

[Edited on 19/8/2012 by ashg]


Not thought of that unless you could turn the box upside down which would give 4 forward.

Just distant pipe dreams, will look for an oldish Alfa transaxle.

Adrian

paulf - 19/8/12 at 09:01 PM

The Alfa transaxles are quite bulky as the flywheel and clutch is incorporated in it, what's up with using a Renault or Audi transaxle ?
Paul
is inc

quote:
Originally posted by AdrianH
quote:
Originally posted by ashg

also adrian how are you planning to use it. in the imp the box is under the rear seats with the engine behind. if you plan to turn it round and use it in the orientation most race cars use you will have 4 reverse gears.

[Edited on 19/8/2012 by ashg]


Not thought of that unless you could turn the box upside down which would give 4 forward.

Just distant pipe dreams, will look for an oldish Alfa transaxle.

Adrian

motorcycle_mayhem - 20/8/12 at 07:28 AM

The gears are quite happy with excessive abuse, Quaife do a S/C 3rd and 4th that helps get the gearing down a bit too.
The differential crosspin (particularly on an old oil-starved box) will shear. If you go for an uprated pin, the differential will then rip out of tha casing. Next step is to weld/strengthen/plate the transaxle. Fit a TranX plate differential and you really can start to abuse the thing.
There's a muff coupling on the input shaft that will break next, but you're well into substantial abuse by now. Abuse that will destroy the uprated (lotus) doughnuts and twist the output spider fingers.

I built a JK 5-Speed (welded casing), TranX, that was happy with a full blown race motor on slicks. Very expensive, not locost.

So... no... look elsewhere. Yes, you can invert the Imp box (Ala Vixen VB4), but that's more grief.

......Turn a Beetle box upside down??????????????? Locost, robust.