i have been doing this for almost 30 years. my expereince tells me the
casues are
a) is the needle bearings are too small in diameter for the loads being
imposed
b) the factory layshaft metallurgy is all wrong,. with a soft centre and
hard shell
there are several options with the factory TR cluster, depending how bad it
is
1) the damaged cluster gear is ground out (not machined, but ground with a
tool-post grinder) and a longer + slightly larger bronze (not brass) bush
is used. if its a race car, use a floating bush with a narrow spiral oil
groove cut on both sides. on a stock road car, the bush can be pressed into
the cluster and it will be fractionally quieter in use that way. When this
box was created for 50HP Standards, they used bronze bushes.
2) the damaged cluster gear is ground out as above and a longer + slightly
larger cased need bearing is used. these are getting hard to find due to
the "odd" size of the stock cluster shaft.
3) a minimally damaged cluster shaft can sometimes be saved by the above
process and a stock sized, but outer cased bearing is used
If you want a 100% never-fail-in-racing, then i use taper roller bearings
at both ends. I first did this about 25 years ago and never had one fail.
BUT, it is a huge endeavour and not justified for a road car (but i have it
in my TR5). it can be done with both Overdrive and non overdrive boxes
the best solution for a road car or occasional track day car is to swap to
the Stag gearbox . These have a double bearing at the 1st gear end standard
and the cluster gear is bigger in diameter at that point, so the bearing is
bigger. they also have needle roller thrust washers, but that's not
important. You need a stag case and cluster gear and late model mainshaft
1st gear to make this happen. There are a few internal changes with Stag
boxes but generally all the TR stuff swaps in .
i'll post up some pics on my work web site or facebook page and let you all
know when i've done that
Terry
Road and Track
66 Pine Mountain Road
North Ipswich, 4305
Queensland, AUSTRALIA
ph 07-32018866
fax 07-32017079
www.roadandtrack.net.au
http://www.facebook.com/RoadAndTrack1
[image: facebook]
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