Drive Shaft Bearing Replacement Nissan 30hp NS30A3

[ARC240]

Engine: 92' Nissan 30hp (NS30A3 - 2cyl. - 2 stroke)
Hi all, I'm wondering how I'd go about replacing the drive shaft roller bearing (the one underneath the water pump & upper case seal) and have a few questions. I've tried searching and I can't seem to find out what exactly needs to be done. I've taken the lower unit apart and it looks like the drive shaft pinion needs to come out, is there any alternate way to hold the drive shaft splines and prevent the d/s from moving so I can crack the pinion nut loose other than buying the Nissan tool? I'd imagine a bearing press would be required once the drive shaft is removed from the gear case to take the old roller bearing off of the d/s itself. Once I press the new bearing on, am I going to have to shim the pinion at all and adjust the backlash on the gears or can I just put it back together and tighten the pinion nut back up?

Any help is greatly appreciated, thanks !

 

[pvanv]

Re: Drive Shaft Bearing Replacement Nissan 30hp NS30A3

The information you need is in the Factory service manual, available from any dealer, including me. I definitely recommend it.

If the bearing is bad, there is a good probability that the LU lube level was low, and the bearing starved for lube. If so, any fragments from that bearing may have damaged gears, seals, etc, so inspect everything very carefully. And... replace all the seals and o-rings while you have the LU apart, since you have already done the labor. The good new is that if you are just changing the o-ring and seal, you can leave the bearing in place. The pinion nut can be removed with conventional/common shop tools. Hint: You can lock the splines in a bench vise. The bearing can be pulled either with a "slide-hammer" type of puller, or a sophisticated threaded unit. Installation can be done either by driving the bearing in with an appropriate drift and a mallet, or if you have access to one, a press.

Now the bad news: If you disturb/replace individual bits in the gear train (including the d/s bearing), you need to verify backlash. That said, if the backlash is correct now... If the bearing comes out completely undamaged, measure its height with micrometers. Compare that to the new bearing. If they are absolutely identical, you can probably use the same shim pack as you had before. That's assuming that the shim pack was correct to begin with. Reason is that if the bearing is a different height, the pinion will have a different engagement into the A and C gears, which you want to correct by the use of the appropriate shims.

 

[ARC240]

Re: Drive Shaft Bearing Replacement Nissan 30hp NS30A3

^ Thank you very much for your answer! Just read that now. The lower unit has never been taken apart since factory, the previous owner never had the seals replaced and (by way of Murphy's law), once I bought it, the seals started leaking . Only reason I'm replacing the d/s bearing is because the d/s and prop seals began leaking (d/s one leaked the worst). I've pulled it entirely apart, all other bearings look fine, the d/s one doesn't seem to be too bad but has a slight bit of resistance when you try to spin it, so I figure now that I'm replacing seals, like you said, might as well do it now. The bearing itself is not in terrible shape, not seriously rusted/corroded, just doing it for preventative measures since the seal right above it was leaking. Discovered that the shim pack actually sits ABOVE the bearing, thought it sat under the pinion as on most automotive differentials. Will borrow a mic from school and do what you told me, hopefully I can just reuse the 2 shims that I found upon dis-assembly. Also, managed to undo the pinion nut by sliding a piece of 15mm rubber heater hose over the d/s splines and clamping that down with a vise-grip and using a ratchet on the pinion nut, came off with ease and the splines remained unscathed ! Thanks for your help pvanv, very much appreciated!!!

 

[pvanv]

Re: Drive Shaft Bearing Replacement Nissan 30hp NS30A3

Yes, the shim pack for the B (pinion) gear (item 9 of figure 13 on page 40 in the parts catalog) is above the bearing. Hint: You can creep up on the lash by adding shims and then re-seating the water pump, until you have the correct lash). Don't forget that there is also a shim pack (item 4 of the same diagram) for the A (fwd) gear as well. Since you aren't changing any gears, you should be able to skip the A-gear pack, assuming that the lash was correct before service. If you don't have the service manual (or have a useless aftermarket manual), I highly recommend the Factory service manual, Part # 003-21035-1 $42.47, available from any dealer (including me) when setting the LU lash.