Extensive damage to gear train. Cause ??

[Stu]

Hi fellow Auto fans,

I've been dismantling a 1275 auto box I acquired recently and saw lots of metal fragments in the bottom of the box. I found it to be due to some major damage to the gear train. I was wondering if anyone knew what could cause such serious damage to the planetary gear splines? There are also missing teeth to the reverse output gear which meshes with the planetary gear.

I think it might be due to misuse, but could also be due to tooth breakage of the reverse output gear leading to the wear on the planetary gear spline, but cant be sure.

For the teeth to break like that I would suspect the reverse gear has been selected too early from drive, or the box has simply been operated too roughly and without due care on up / down-changes.

It could be something else but the gear train is toast for sure

Interestingly though, I can report that this box, a later one with a park facility, has a different valve block from the standard no park box. It houses a lever which engages into a toothed sprocket on the end of the forward clutch for park when selected. The selector shaft has a very short coned shaft around it which, when engaged, pushes the park lever to engage into the sprocket to provide the park. It basically locks the gear train in position. I assume the selector would need to be in 'N' to allow the car to be started due to the inhibitor switch, which would disengage Park and allow the gear train free movement ready for drive or gear selection.

The more I work on these boxes the more I like them, its just sad to find damage. I'm still working on trying to dismantle the gear train, but I need a special service tool to remove the gear spindles, and I cant for the life of me get the locking ballbearings out. ''Give the gear train a light tap with a hide faced mallet to jar the locking ball out'' says the manual ...... Yeah right 

[jockduck]

Dun no Stu, I always heard that the gear train was very robust and practically never required any rectification but someone has proved that wrong, must have gone off with quite a bang. I digress a little, A woman once told me that on passing her driving test she took the family car out for the first drive on her own(in Australia driving a HR Holden with 2 speed Powerglide automatic) while driving along in "D" at 50 mph she wondered what would happen and selected "R" The car screeched to a halt with rear tyres smoking, she reselected "D" and drove off with no damage to the transmission! The powerglide is a great autobox still used in dragracing.
Jock

[Stu]

Thanks Jock. Interesting point. I got the box for spares so I'm not too concerned, but I like to try and understand how damage occurs just for knowledge etc.

I'll put that one in the ?? box for now then.

[mra-minis]

that is commonly known as mechanical failure... before the new type of bevel gears the 2 bevels used to separate and then free wheel !

One thing you could look for is a worn bush, shaft or bearing allowing a little movement..