auto trans flex plates, do they need to flex? can I use a flywheel?

[jase]

ok a question
an auto trans flex plate, does it need to flex? can I use a flywheel instead (this obviusly wont flex??)
reason I am making an adaptor plate to fit HS2.8 to V8 bellhousing, (using a tdi bellhousing from a disco the engine is too far back in a RR P38, the V8 bellhousing is longer + the thickness of the adaptor plate will put engine in the right position)
I'll need to space the torque convertor off the std flexplate by something like 40mm (am waiting to get together to measue exactly) I'm a bit worried this is a long way for spacers, But if I use a flywheel instead of a flex plate (and the engine comes with a brand new flywheel) the spacer thickness would be reduced due to the flywheel thickness. But it would be very solid and wont flex, is this a bad thing ?
looking for pros & cons

thanks
Jase

[rovercare]

As far as i know the whole idea of the flex plate is to put the ring gear on and start the motor,i really don't think they flex at all, the big problem i think you'll have is the additional weight you'll be adding to those little bolts in the crankshaft, personally i'd get a flex plat and adapt from there, but thats just my thoughts

[loanrangie]

Jase, the v8 rangies with zf's use a thick spacer to adapt the t/converter to the v8 flexplate and it would be very close to 40mm. Also the extra weight of the flywheel may cause problems with the t/c in that it may not slow down enough to allow the auto to coast properly without load on it.

[p38arover]

Jase, the v8 rangies with zf's use a thick spacer to adapt the t/converter to the v8 flexplate and it would be very close to 40mm.

Not on P38As - I had my gear box out recently to replace the shattered flex plate.

Ron

[jase]

hmm no spacers in my P38 either (that's what I'm working on)
maybe it's due to the larger torque convertor ??
I'll checkout an older RR for spacer design
thanks
J
PS I had thought of pros and cons of higher flywheel mass, might be an advantage on low RPM deisel?

[loanrangie]

I was refering to classic rangie's with zf auto, they needed a thick spacer to take up the distance between flexplate and t/c, something similar is what you need. Maybe tdi auto's have a similar spacer ?

[DEFENDERZOOK]

the flex plate does not flex.......

you need some weight to keep the engine spinning between the strokes of the cylinders firing.......
the manuals use a thick flywheel for this......
the autos use the weight of the torque converter......
if you bolt the torque converter to the manual flywheel.....it will take a fair of power to simply rev the
engine in neutral......then...once you manage to get the revs up.....they wont want to drop in any hurry......

ideally....for perfomance....flywheels are lightened to allow the engine to rev faster......and to drop back to idle quickly
for maximum engine braking......

if you want to use the manual flywheel.....have the uneccessary metal machined off.....
the bit where the pressure plate bolts to and the bit where the clutch plate runs.....
basically a lightened flywheel.....but take care not weaken it......it is a job for an engineer......
not a backyardie with a lathe......

[BigJon]

Also keep in mind how you will have to bolt the torque convertor to the flex plate / flywheel. The clutch usually bolts to the rearmost face of a flywheel and there are threaded holes in the flywheel to cater for this.
A torque convertor has threads in it and the bolts pass through the flex plate and bolt into the convertor. You would need to drill appropriate holes in a flywheel to allow for this.

[HSVRangie]

When I swapped engines:

I had my own spacer made up and flex plate to suit.

fit bell housing.
fit t/c

measure fronm crank to t/c and make to suit.

bolt the flex plate on with the same bolts as the spacer.

simple and easy.

and marks use the flywheel in thier conversion.

I just did not want the extra weight spinning.

MIchael.

[RR5L]

Also keep in mind how you will have to bolt the torque convertor to the flex plate / flywheel. The clutch usually bolts to the rearmost face of a flywheel and there are threaded holes in the flywheel to cater for this.
A torque convertor has threads in it and the bolts pass through the flex plate and bolt into the convertor. You would need to drill appropriate holes in a flywheel to allow for this.

Thats exactly what I have done with the Flywheel on my conversion, though now Im wondering if I should of gone the other route with the longer adaptor like HSV suggested.