what causes main shaft bearing failure ?

[8622r]

well.....
i picked up a g54 trans to replace my g52 that falls out of 5th g3ear
looks like i may have wasted 100.00 oh well.....
so i take it apart looks good inside it had oil
1st thing i find is the input gear has 1 broken tooth going back from that
point everything else looks ok until i find the small 5th gear? is missing a tooth
so i do a little more looking and see some of the ball bearings are missing out
of the inboard main shaft bearing and of i did find most of the cage in the housing
just wonder how commin is this failure? can i still run this missing part of teeth?
and is there any modification that can be bade to prevent this from happining again?

[79coyotefrg]

i think Marlin makes some sort of thrust plate  for some trannies  that helps with this,  but  bearing failuer is probably the main problem

[Uncle Jesse]

I rebuilt my brothers transmission a while back.  The input mainshaft bearing was completely destroyed.  The intermediate plate bearing was intact.  I can't prove it, but I believe his bearing failed due to way too many forced 2nd to 1st downshifts.

I would imagine that you would need to replace the broken gears, as they are most likely stressed, and could break again.  Also, I would imagine that you would get some gear noise.

[8622r]

i do think it was the intermediate plate bearing
that came apart

[8622r]

and on another note i got a good screwing for a second time
the second transmission i bought does not in to 1st or 3rd

[79coyotefrg]

[Uncle Jesse]

time for a rebuild

[Marlin]

A helical gear by design will always case a side load. This load will be one direction on acceleration, and opposite on deceleration.
This side load in time will wear out the roller bearings.
This forward and rearward movement allows the gears to run out of line and then the teeth fail from fatigue.

When the trans is rebuilt, I spend special attention to reduce the mainshaft endplay.
I also invented a G54HD trans that has a wider, stronger rear mainshaft bearing.

[8622r]

A helical gear by design will always case a side load. This load will be one direction on acceleration, and opposite on deceleration.
This side load in time will wear out the roller bearings.
This forward and rearward movement allows the gears to run out of line and then the teeth fail from fatigue.

When the trans is rebuilt, I spend special attention to reduce the mainshaft endplay.
I also invented a G54HD trans that has a wider, stronger rear mainshaft bearing.

so what i ended up with on the used g54 i got  intermediate plate bearing had 3 rollers left in it
the input gear had 1 chipped/broken tooth and the little 5th gear(the small gear it sefl)
has 1 chipped/broken tooth the rest looks like new.

i did do some reading on the g54hd transmission you invented (i was going to order one)but was never able to get an answer
as if my g54 had any core value with the 2 dammaged gears.

[8622r]

i love to post a picture of the two dammaged gears (input and 5th)
but i do not know how to make them smaller
(i am not that good with the poto side of computers...yet)