Chrysler gear case Bevel Pinion clearance

[drewpster]

I have completed the tear down of the lower unit and gear case of my Chrysler 70hp. I am planning to replace all the bearings. IS there a way to set bevel pinion/ bevel gear clearance without the special "checking tool" in the factory manual? Mine is an older outboard. I am sure finding one of these tools is going to be next to impossible. Can I pattern these gears instead of using the tool?

 

[Frank Acampora]

Re: Chrysler gear case Bevel Pinion clearance

An old Chrysler mechanic once told me that the Chrysler lower units were set up "loose" and were very tolerant of clearance. Well. I'm not so sure.

BUT. Some forward gears were shimmed between the gear and inner bearing race. Since bearings are maintained at very close tolerances, I would re-use the shim if it is there. The pinion itself may be shimmed the same way and if shimmed it is held in proper mesh by the roller bearing seated between the two gearcase halves. Again, I would use the existing shims (thrust washers) between the prop shaft and forward gear, and the shim pack under the rear roller bearing outer race (inside the gland that seals the lower unit and carries the prop shaft--two screws hold it to the lower.)

My line of thinking is that again, bearings are held to very strict tolerances and the various shims are there to correct machining tolerances of the lower unit casting itself. By using the existing shims or new ones of the same thickness, you will most likely be very close to the way it came out of the factory.

Be aware that removing the inner races (cones) of the pinion and forward gear is very difficult unless you have a thin bearing puller (screw together type) and a press. If they are not damaged, it is way easier to leave them be.

 

[drewpster]

Re: Chrysler gear case Bevel Pinion clearance

So in your general opinion if I use the same make and part number bearings, ( Timken) I should be ok re-using the factory shims. Correct?
The bearings look ok but they feel rough turning. (no visual pits, no flaking or metal in oil) There is some discoloration on the races short of actual rust. I know I had a small amount of water contamination, but I have been good about keeping the dope changed. I have bearing tools at work (pullers and such) and a 100T press as well as bench arbor press. My concern was that the manual uses tons of specialty tools to set up the gears. I guess it is like everything else, nobody but the factory has all those tools.
BTW- Timken still lists all the bearings, but the upper main shaft bearing is $30 alone. Geez! Marine-add 40% in price, 100% in effort.
I have never been very confident reading roller bearings. Unless they have some good pits I am never quite sure. When in doubt, change them out. Right?

 

[drewpster]

Re: Chrysler gear case Bevel Pinion clearance

One more thing. I noticed some pretty good grinding of the clutch when shifting the gear box in times past. I have been using Pennzoil lower unit lube in the gear case. You think another brand or weight could quiet some of the raking?

 

[tjello327]

Re: Chrysler gear case Bevel Pinion clearance

As for the pinnion gear depth setting goes, The most important thing that must be watched is to make sure you have about .005" to at the most .010" backlash between itself and both of the forward and reversing gears. I was told that the drive shaft (pinnion shaft) when properly shimmed under the outer bearing race would have a little end play up and down in it. My bearings are in good condition and I was worried about some end play I had in my drive shaft. The advice I got from this forum was that when the gears are in mesh, The helix of the gears will pull the bearing down into the outer race. I was going to make a pinnion depth setting tool at work but there is one diameter on it I dont know and its the important one you measure from. So I am in the same boat your in as for setting the pinnion depth. I have set up a few ring and pinnion gears in race cars and I do understand pinnion depth and backlash. My theory for lower units should be the same as a properly set up ring and pinnion in race cars which is like you said in your first post, use marking compound to get your gears to ride in the middle of the teeth, not to high and not too low. Once you get this set, put an indicator on the gear that can be reached and carefully check backlash. I have set up enough gears so I can carefully "feel" for backlash by hand. Remember, there must be at least a little backlash. None is going to destroy the gears and then everthing else. One bad thing about lower unit gears are that when you set the pinnion depth, this also affects your backlash. You cant set pinnion depth and then fine tune backlash like you can in cars. Hope this help with your lower unit!

 

[tjello327]

Re: Chrysler gear case Bevel Pinion clearance

Oh yeah, as for the grinding noise goes, Check your drive dog between the forward and reversing gears and the gears where the drive dog engages. They may be loosing the flat face that does the driving from years of wear. I came up with a machining repair for both gears and the drive dog. If yours are in bad shape, feel free to send me a private message and I can work something out to save you $$$.
Thanks!

 

[Frank Acampora]

Re: Chrysler gear case Bevel Pinion clearance

I made the assumption that your lower unit was a 2 piece lower, but your remark about the upper bearing cost now leads me to believe it is a one piece lower.

The only adjustments on the one piece are to prop shaft end play and pinion depth adjustment.

You can adjust pinion depth without the tool as long as you note the mating surfaces of the teeth while the gears are out. There will be a definite "wear" pattern on them and you would want to match that. Then with some sort of dye on the pinion (maybe Dykem) you note if the teeth are meshing properly when assembled in the gearcase; Again, if you use the same shim pack that was under the original bearing, you should be very close to factory original settings. As Tjello wrote, it is very much like an auto rear end and there is a definite "sweet spot" that you can feel.

Prop shaft end play is between .006 and .010. It is adjusted by the thickness of the hardened steel thrust washed in the center of the forward gear. A small excess seems not to hurt anything but too little end play will cause wasted power and possible wear of the prop shaft land (that rides against the reverse gear during reverse operation).

As for grinding, these are dog clutches and should be "snapped" quickly into gear. Do not ease them thinking you are doing good. This rounds the mating surfaces and if continued, leads to the engine popping out of gear under load.A definite clunk should be heard during engagement.