Lower Unit Gen One Rebuild

[Chris51280]

I need some advice. I got a lower unit that was what I thought seized up. The upper unit is seized up due to being run without enough oil in it. Lots of discoloration. When I got the lower unit split from the top I could not move it in forward or reverse. I pulled the bearing carrier out the whole unit spun freely. After inspecting the unity, it looks ok. each bearing runs without any problems. The rear thrust bearing has marks on it but no noticeable damage other than the roller marks. I thing it got overheated as well. The gears look to be ok. What is your take on it. I have a complete seal kit and I think if I just replace the forward angular roller bearing I should be ok.

 

[Chris51280]

If I just replace the bearing, Do I need top re-shim the assembly. I assume that bearings are made pretty close to each other

 

[Scott Danforth]

you need to go thru the proper shimming process. bearings are not that close.

 

[harringtondav]

I see very good, usable parts in your pics. I'm with Scott Danforth , You should use the shim tools, The gear sets were matched near dead nuts at the factory, and the shim tools will get you back there. I've had to adjust shims up to .007" with new bearings. That much off will cause a whine at best, pitting and eventual $$ at worst. I've got two fiends with replaced lower hsgs. The shop said "They make those hsgs. perfectly the same". ......whine, whine, howl, howl.

 

[Chris51280]

I will take the cone side off and look what timken bearing number it has. I will then order a set and compare the height between the bearing sets. If the newer bearing is higher, I know to take the difference off. If it is shorter, I will order a shim set and have it ground to what I need. I think the other bearings look ok. Just the forward thrust bearing is not the greatest anymore

 

[Grub54891]

I will take the cone side off and look what timken bearing number it has. I will then order a set and compare the height between the bearing sets. If the newer bearing is higher, I know to take the difference off. If it is shorter, I will order a shim set and have it ground to what I need. I think the other bearings look ok. Just the forward thrust bearing is not the greatest anymore

Even the gears are a bit different from one run to the next. You really need to set them up with the proper shimming tools.

 

[harringtondav]

You may be OK doing this on the big FWD bearing. This is the only spiral bevel gear that's not set with a shim tool. There is an elaborate process to set the backlash in this mesh with shim adjustments behind the cone. But the tolerance is fairly generous.

Problem is you'll have to cut the roller cage to to get your bearing separator on the small rim of the inner race to pull it off the propshaft. This is per the manual, and I haven't found any other way. This will ruin any chances of getting comparative heights. So put back the shims, and keep your fingers crossed. The factory tries to hit mid range on the backlash tolerance.

Be sure to torque the pinion nut back on the vertical drive shaft @ 70 ft lb., and apply green loctite to the nut threads. Push the propshaft hard fwd. with your carrier puller to seat and immobilize the shaft. Pull up hard on the vertical drive shaft and give it a jiggle back and forth. This is a poor man's backlash check. I believe min. is .019", max around .040". Too tight, tear it down and remove shims. Too loose, add.

 

[Chris51280]

I cut notches onto the top ring of the cone. Roller and cages removed. Tomorrow at work I will have it removed with a bearing separator.
What about the large ball bearing that sits behind the reverse gear. I believe that one can be changed without any adjustments, correct?

 

[harringtondav]

I cut notches onto the top ring of the cone. Roller and cages removed. Tomorrow at work I will have it removed with a bearing separator.
What about the large ball bearing that sits behind the reverse gear. I believe that one can be changed without any adjustments, correct?

Yes, no shims. But when you pull the REV gear, the bearing may or may not come with it. If it does, your bearing separator will get it off the gear. If not, you'll need your slide hammer again to get it out of the carrier. Use a socket to push out that Torrington needle bearing, and the two old seals with it. Replace the needle while you're at it. It's fairly inexpensive.

The fussy part is reseating the needle. It must seat at the bottom of it's bore, but not be crushed at all. Merc. drivers set the distance from the face of the carrier. Same w/the first black seal in. The lips and garter spring face in. Get it deep enough to start the shielded outer seal, and let that seal drive it home, with the outer seal flush. Pack the space between the seals w/Merc 2-4-C waterproof grease.