Need some gearbox seal advice

[jtexas]

1979/70hp. Found a tiny bit of water in the gearcase, underwater pressure test indicated driveshaft seal. Removed bearing housing, found 2 damaged shims. These are the shims that ride underneath the bearing housing.

The guy at the parts house calipered 'em for me, 1 @ .002 and 1 @ .001

Parts list doesn't even show a .001, and .002 is discontinued/not available, so I have a .003 on order.

first question: I'm kinda second-guessing the parts counter guy, on account of I have no experience..........could there have been a .001 in there or is there a chance of measurement error. should I be looking for a .004?

next question: these shims both broke along a concentric ring around the center, leaving what appears to be a perfectly good shim with an extra large inside diameter (pic attached). Just how crucial is the inside diameter?

How common is it for these things to break? seems kinda unlikely to me.

Would you reinstall these?

thanks!

 

[jtexas]

Re: Need some gearbox seal advice

^^^

 

[Scaaty]

Re: Need some gearbox seal advice

I'd find a parts diagram of the gearbox (ya don't say what motor). Just to see what it shows.
Me, I'd Mic or Caliper the thickness of whats in there. Stick with new same size.
I'd figure out what caused it first. Don't make sense to me..

 

[jtexas]

Re: Need some gearbox seal advice

its a 1979 70, only one model # for that year/hp (70973). parts list shows .002, .003, .004 and .005, but .002 is out of production. Which is why I'm skeptical about the ".001" measurement - it was the parts counter man, not a tech. Of course, part #'s aren't stamped on 'em. Think I'll acquire a mic & take my own measurements.

According to the manual, these shims set the precise height of the pinion gear (zero tolerance). Re-seal wouldn't ordinarily require removal of the driveshaft, but to measure for new shims does, and I don't have the tools for that. Wasn't going to tear it down 'cause no other symptoms (metal in oil, vibration, noise, shifting probs, etc.).

I was wondering if it's common to encounter that kinda damage. seems like it could only happen if there was some play in the driveshaft, which I woulda sworn there wasn't a year ago last time I dropped the L/U. hit a submerged object at WOT about 4 years ago, motor kicked up, apart from some cracked glass around the motor mounts, no apparent damage. the 20 years before that, who knows?

any other opinions/comments, feel free to chime in................

thanks,

 

[Scaaty]

Re: Need some gearbox seal advice

OK, had to re-read yer post. Ya had me on "under the Bearing Housing", as I thought we were talking prop shaft seals/carrier..that area.
So ya say ya pulled the driveshaft/pinion? Thats where the shims came from? Thats critical. If those shims wore through, it was to tight, like it not enough clearance... or ..jeezz, a rough one.
Do you have a manual, showing Pinion clearence setting? If ya got the guts out, I would do a full rebuild (all seals, etc/look over)..the pinion needs to be set right..spiral gears are touchy, and its a good Pinion setting that well keep them from tearing each other up....
Maybe FR will chime in here..he knows those cases better than I ever will.
Basically, you need to set the Pinion with the proper clearence on the forward gear (as its up against the forward case bearing and not moving, and there can also be shims there too. ..)
Its explained in the manual.
Hang in there, we will get it figured...keep bumping until others get involved..

 

[Scaaty]

Re: Need some gearbox seal advice

OK, thinking of this, I would replace any driveshaft bearings (cup and cone) first. If beyond what ya can do, take it to any local machine shop. Those DS bearings might be worn (probably available any bearing supply, online easy to order..#'s stamped.), and the slop trashed the shims
Brain working here, but not sure if I'm in "gear"..(pun intended!).

 

[jtexas]

Re: Need some gearbox seal advice

I didn't pull the driveshaft, just removed the top bearing housing to replace those oil retainer seals. The manual specifies a "special tool" for measuring clearance from top of pinion gear to bottom of bearing housing, but doesn't give the actual distance.

the bearing looks fine (what you can see of it, under the thrust washer)...didn't think about 'em wearing down..................

still hoping to avoid a complete tear-down...............

thanks,

 

[flabum]

Re: Need some gearbox seal advice

If they don't look like they spun in there, I'd re-use them. As long as they are doing the shimming, you will be ok. Again: AS LONG AS THEY DIDN'T SPIN.

I have seen this from time to time....they simply sheared where there is no support for them.

 

[Scaaty]

Re: Need some gearbox seal advice

OK, I just went at looked at BRP. You talking PN#36 (shims).
I'd go with new shim/s. I'd get a Mic or Caliper and do a second check. Get as close a match as possible, then wrap it up tight, and spin the DS. Free and easy, with very little (if none) up/down slop, good to go. If not, then re shim accordingly

 

[jtexas]

Re: Need some gearbox seal advice

can't be sure they didn't/won't spin, but no doubt spinning would tear 'em up - nothing but pressure & friction holding the shims & thrust washer

I'm ok with replacing 'em, it's just a question of how much - might need more thickness than I took out. I was going to ask if I torquing it down & checking for play in the driveshaft would be acceptable practice - answered before I ever even asked........dam you're good!

thanks,

 

[Scaaty]

Re: Need some gearbox seal advice

21 years Maintenance Machinist...you break'em, I make'em!..kinda comes natural..
Shims probably cheap...get a few..then use the most excellent instrument known to man, never can be re-produced from China...fingers and feel..
Don't put the old crap in...little tiny piece of shim gets in the bearing..well, ya know the rest...
Be nice though if you could get someone with a Dial Indicator..(Harbor Freight has them cheap, as a digital Caliper...)..then you can check the up/down shaft movement...(kinda hard to feel 1 thousandths of an inch)..and shim thickness easy check with a Dig Caliper..although I prefer my trusty "Mics"...calibrated..
Spiral gears are (again)..touchy..I use Dykem "Steel Blue" on gears. Shows the gear pattern (wears it off..formula's in my Machinist books for setting clearence)..but we aint talking rocket science here..
Remember...heat will increase with running, so more "slop", better than tight cold..and the gear oil film..which will add a thou our better easy..so do not do it dry. Go for it..