Gear mesh offset - how bad is this?

[vandor]

Hello,
I am putting a Polski Fiat 5th gear into a Fiat 124 gearbox. It's close, but not an exact fit. After machining a few parts this is the closest I can get (see picture). The gear overlap between gearteeth is 70-80% of the width of the teeth, instead of the ususal 90-100%.
How bad is this? Will it work or is it likely to fail? This gear would be used for highway cruising, not racing or spirited driving.
BTW, moving those gears for better overlap is very difficult, as it effects many things in the gearbox.
Thank you in advance,

Csaba

[TR-Spider]

Hi Csaba

I can not tell what happens with the gears running at such overlap, but I would not have a good feeling doing it...

cannot you correct the the overlap simply with a shim, see picture?
Maybe a picture of both 5th gear sideshafts beside each othe would be helpfull.

Thomas

[vandor]

Hi Csaba
cannot you correct the the overlap simply with a shim, see picture?
Thomas

There is already a shim there. If I shim it out more the teeth of the 5/reverse double gear will be barely engaging into the shaft.
I think I just need to play more with the shims for other gear, but it's not easy as it affects the neutral location of the shiftfork.
You are right, the offset can't be a good thing.
Thanks,

Csaba