[Fot] Gearbox thoughts

[Dean Tetterton]

Boy, Lots of good thoughts on this. Still lots of unknown's. Where are the engineers, Ha!

First off Glen is right, one needs to change the gear oil to keep the ground up piece's
of metal to a minimum. Cheap to do and doesn't take that long. I even run a second
magnetic plug in the fill hole.
Second could not agree with Steve more. Double the bearing area is a good help. I have
a question as to the TR4 press in bearing. Good in it gives more bearing area with the
small rollers but I feel it suffers from oil flow. Is there any why to improve on that? I use them
a lot but would feel better if I could see a way to get more oil thru them. I have pulled apart
boxes where the rollers are packed with crud. 
Third with the helical cut gears, there is a bit of pressure applied to the thrust washers as they
try to push away from each other. Would the needle bearings help with that? Who knows?
Is it worth the expense? Guess the answer here is straight cut gears. Yeah, a dog box...

Still lots of questions but nice to hear what other people think. We need to get together
with some cold one's and solve all these problems. 

How about a T5?

Dean T
Never stop improving the equipment.





On Oct 15, 2015, at 1:49 PM, Steve Yott wrote:

> I have had the opportunity to rebuild many TR gearboxes and a handful of
> Stag boxes and would like to offer my opinion and that is what it is... my
> opinion.
> 
> The Stag box added a lot of complexity to the area of the laygear and shaft.
> The layshaft is different in that it has two outside dimensions that match
> up to the spacers for the needle bearings. Now you have needle bearings,
> spacers and thrust washers.  I am basically not a fan of this arrangement as
> there are many more parts to fail and the needle bearings are known to fail.
> Where the Stag laygear does benefit is from having two rear bearings!
> 
> The real problem occurs when excessive torque on the single rear bearing
> causes the bearing and or shaft to fail.  Once there is play in the bearing
> to shaft fit the laygear starts floating up, down and side to side which
> then causes non-parallel loads on the bronze thrust washers and they begin
> to fail.
> 
> I have bored a good number of laygears to install double rear bearings in
> the rear of the gear.  I do not use the "open cage" bearing as the TR6 uses
> but I use the TR4 type enclosed bearings.  I do this operation on all
> gearboxes I rebuild now because I am sold on this fix.  The bronze thrust
> washers will withstand the loads on them as long as they are square with
> each other and the laygear end float is properly set and I use no more than
> .006" of end float.
> 
> Just my opinion!
> 
> Steve Yott
> 
> -----Original Message-----
> From: Fot [mailto:fot-bounces at autox.team.net] On Behalf Of Dean Tetterton
> Sent: Thursday, October 15, 2015 9:20 AM
> To: FOT Triumph
> Subject: [Fot] Gearbox thoughts
> 
> Since we have been thinking about gearbox's. The Stag layshaft was changed
> by Triumph to try and make them last longer due to the additional torque of
> the V8. They added needle bearings in place of the brass thrust washers at
> each end and an additional bearing  in the lay gear at the end where 1st
> gear is. Has anybody tried this set up in a racing box? Does it help in the
> wearing of the layshaft? 
> 
> The addition of needle bearings means that the spacing of the box inside
> where the lay gear rides is greater. The needle bearings being thicker than
> the thrust washers. This means that the Stag box is different inside. 
> I have been able to make a tool that will cut the inside of a TR box to be
> the same as a Stag. I plan to build a box using the needle bearings. Don't
> at this time plan to put another bearing inside the lay gear. If I make the
> lay gear deeper inside, I am afraid it will not be hard enough for the
> bearings to ride inside. 
> 
> Before doing all this, has any body gone down this road before. If so what
> has been the experience? 
> Also any body with thoughts chime in. Is it worth the effort?
> 
> Dean T.
> 
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