Panther

Wow, that's make or break!

So basically your pinion depths are staying pretty consitent but you're having to continually shim the race on the driven gear in the lower?

Boater8987

Sorry to change the subject guys, but is there a way to mic or measure the wear on the gear teeth to determine if the upper or lower gear sets are useable or not? Besides looking at them. Thanks for the great imfo guys. Always a pleasure to read and learn from your threads.
Thanks Gary

Mr Gadgets

I see more variation in the bearing races which causes the gears to move around some. Generally I dont measure the lower gear pinion height, if when tearing the drive down I see bearing wear. I think about it about 10mins after it is too late.. So I generally build from scratch and things get shimmed accordingly. I just did a drive that had a lot of hours on it.. and the tapered bearings look like new. It needed a new set of lower gears and without changing the shimming the gear lash fell into place.
The variation of lash is due to the net forging and what ever surface that the gears have on them. Be it nitriding or what ever. Not much you can do about it. I was hoping that the cryo treatment and polishing would help that, but it doesnt seem to. Although it doesnt seem to matter unless you get to serious power, from what I have experienced. I had a run of upper gears that were all over the place on lash, and they are holding up fine, even in high stress setups.
Gary, there isnt a way to measure the gear wear. It is more of a visual thing. Which gears are we talking about.. uppers, lowers, XR, helical?? The near net forged will start to show a line in the middle of the tooth and then give up metal as they are run.. If you can catch it before the tooth breaks off.. you got all the milage you can out of that set of gears.. The helical will shine up and wear till they break teeth.. usually a long run when behind mild power..
Hope this helps..
Dick

Panther

Thanks Dick, that's what I've seen as well! Just wanting to see if I was missing something.

Garry, when your gears look like the first picture just throw them out because they're near the end of their lifespan. The second picture is earlier on in its life and the shotpeen is wearing away and the teeth are getting shiny.

Boater8987

Hey Guys, many thanks for the imfo. I have worked my way up thru exploding, all the bravo styles since 1987 currently running XR with sportmaster lowers. Around here nobody rebuilds bravos, at least none that I trust, the dealers only want to sell you a new one when a drive breaks. So I have been learning by trial and error, plus the merc manuals to build my own drives along with a friend of mine. Now that I have high speed internet, much has been learned in the last 5 mo. from all of the imfo you guys share. By the way I too would like to know how do you get the middle bearing out of the upper XR gears without destroying it? Again many thanks for the imfo.
Gary

Panther

I believe it's part number; 91-31229A7

Boater8987

Thanks for the tool # Frank I will order that from Merc.

fountainfevr

im in the middle of putting my drive back together it seems to me ( and this is my opion im a auto refinisher not a mechanic) that the only thing you are shimming is the case so if you are using the same case you should be ok. Am I close to being right?

Back4More

I will need some of those cryo lower gears sets very soon....
Will be rebuilding this winter.

articfriends

Besides the small lines you may also start to get tiny pits that sorta look like cavities,once you get them they start opening right up and the gear really starts to give off a ton of metal,when you start seeing a higher amount of metal in your oil when changing it and feelng a little gravelly feeling when spinning the prop its time to tear the drive down before you really destroy it,Smitty