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Re: TR6 Flywheel

To: Mike Rose <>
Subject: Re: TR6 Flywheel
From: Randall <>
Date: Sat, 27 Oct 2001 11:13:13 -0700
Mike Rose wrote:
> I have been receiving conflicting advice from a couple of sources and I would
> appreciate it if anyone can tell me for sure whether a TR6 flywheel will fit a
> TR4 crank.

Not without a _lot_ of modification.  The 6-cyl crank flange is smaller,
so is the bolt circle.  (I've got both engines sitting in the garage at
the moment, so I double-checked.)
> And, if it will fit, will the TR4 starter engage the teeth on the TR6 ring
> gear.

No.  Different tooth pitch, and the bevel is on the wrong side. 
However, I believe the ring gears will interchange, it's possible to
mount a TR6 starter to a TR4 engine by milling away the mounting flange
a little, and using the TR6 ring gear.

> Will the TR4 transmission input shaft work with the TR6 flywheel and TR6
> clutch disc & pressure plate?

I believe so, if it's an early TR6.  

At some point, the TR6 pilot bearing moved from the end of the crank,
into the flywheel, and the transmission input shaft got correspondingly
shorter.  However, the later shaft will supposedly work with the early
pilot bearing (although bearing engagement is minimal), so presumably
the opposite is true, if you cut off the excess length of input shaft. 
I don't know for sure tho, so check carefully for interference between
the input shaft splines and the later pilot bearing.

> Are the transmissions (complete) from the TR3/TR4/TR250/TR6 really
> interchangeable?

To some extent, but there are lots of little changes that have to be
accomodated.  For instance, the TR4-TR6 all-synchro boxes are slightly
longer than the TR2-3A 3-synchro.

>  I have a TR4 transmission and a TR250 transmission.  Will I
> have a problem interchanging them without changing the clutch?

I believe it can be done.  The nose piece on the transmission has to be
changed, the one used with the diaphragm clutch (TR4A-TR6) is somewhat
shorter than the one used with the finger (TR2-TR4) clutch.  The
mounting studs in the block may have to be changed, I believe the TR250
mounting flange is thicker.  The TOB is different, I'm not sure offhand
about the sleeve.

> Would my best bet be to have my TR4 flywheel drilled to accept a TR6 pressure
> plate?

Given all the trouble the TR6 folk have with clutches, I'd say the
answer is no.  However, it is lighter ...


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