Alpha 1 Gen II drive shaft bearing preload

[G1K]

OD serial: OD732853
I'm having a heck of a time getting the preload set to the specified 5.25 in-lbs.

I needed to replace the yoke and seals on the drive shaft. After replacing the oil seal I put the gear and bearings back onto the old yoke to get a feel for tightening the nut to achieve the proper rolling torque.. I overtightened the nut and would up with a rolling torque of 10 in-lbs. No big deal, I needed to put on the new yoke anyway..

So I pressed off the bearings, and pressed them back on following the instructions in the manual. I put on the gear/bearing asm. on the new yoke and installed a new nut and tension washer. I tightened it finger tight and started checking the rolling torque. It was ~3 in -lbs. I turned the nut in 1/8 to 1/4 rotation increments and checked the rolling torque each time. When I got it to ~4.25 to 4.5 I tightened the nut just a hair more and the torque jumped to 6 in-lbs.

So now the plan is to press the whole thing apart again, and then back together and repeat. What's the trick? My plan is to get it to 4.25 to 4.5 again and then tighten 1/2 a hair and see if that works.

Also, the rolling torque is dependent on the rpm. the manual states after 2 full turns, take the reading on the 3rd revolution while turning slowly. How slow? 1 rev in 6 seconds? 1 rev in 10 seconds?

Last question, the bearings are pretty tight on the shaft. I can see over or under pressing the bearing farthest from the gear is a very easy thing to do. The manual states to press until the rollers make light contact with the cup. Is the remaining distance the bearing is supposed to travel down the gear shaft to be determined by tightening the nut? Or does the distance the bearing is pressed a thing you get a fell for after doing enough of them?

I know that when I stopped the press when the bearing rollers made light contact with the cup, there was still A LOT of play left...

Ryan

 

[rodbolt]

Re: Alpha 1 Gen II drive shaft bearing preload

on used bearings? Ill buy 5-9inch pounds.
use the bearing retainer wrench locked in a vice so the shaft hangs vertically.

 

[Don S]

Re: Alpha 1 Gen II drive shaft bearing preload

Impossible to say without seeing the bearings, but I would bet money your bearings are bad, due to metal transfer from the oil. The surface will look more like formica instead of a smooth bearing surface. A good quality HD closeup picture of the race would answer the question.

 

[G1K]

Re: Alpha 1 Gen II drive shaft bearing preload

on used bearings? Ill buy 5-9inch pounds.
use the bearing retainer wrench locked in a vice so the shaft hangs vertically.

The manual is very specific, used bearings are to be set at 5.25 no more no less. Actually there may be a mistake in the manual... manual 14 section 3a page 26:

[5.25 lb-in. (0.55 Nm) for used bearings] in one sentence, then a few sentences down:

[5.5 lb-in.
(0.55 Nm) for used bearings]

these are not equivalent statements... I'm gaoing to assume the second sentence should read 5.25 not 5.5..

but that is the way I am doing it, with the wrench in the vice and the shaft hanging vertically.

Ryan

 

[G1K]

Re: Alpha 1 Gen II drive shaft bearing preload

Impossible to say without seeing the bearings, but I would bet money your bearings are bad, due to metal transfer from the oil. The surface will look more like formica instead of a smooth bearing surface. A good quality HD closeup picture of the race would answer the question.

Don,
I will take a pic on Monday when I am able to press them a part again and post it up here.

Thanks,
Ryan

 

[ziggy]

Re: Alpha 1 Gen II drive shaft bearing preload

when it came time to decide weather i should replace my drive gear brg. assy. it came down to this statement that was made to my by my local merc. mech. if a brg. is in question for any reason, replace it. the service manual is pretty specific as for things to check to. "check tapered roller bearings by inspecting bearing cups. replace bearings and bearing cups if cups are pitted, grooved, scored, worn uneven, discolored from overheating or have foreign matal particles embedded in the cup." i just replaced mine on a 1 drive for being blue.....

 

[G1K]

Re: Alpha 1 Gen II drive shaft bearing preload

Lets assume that I do have to replace the bearings. (Maybe for $80 it's cheap insurance). Looking on mercstuff.com I found this:

http://www.mercstuff.com/doublebearings.htm

part number: 0382.

Unfortunately these (at least by the pic) do not look like timken bearings, but some imported ones. For something this critical, I think I'm going to try to find the timken ones. I have a very good bearing supplier near me that should be able to give me the correct ones.

Thoughts?

My simple drive oil change is turning into quite the experience. Well, at least I know it'll be done right and will hopefully be trouble free for the next 15 years.

Ryan

 

[rodbolt]

Re: Alpha 1 Gen II drive shaft bearing preload

5.25inlbs, rotating by hand with a dail indicate torque wrench with a zero tolerance?
hahahahaahah your smoking something. aint gonna happen. kinda like volvo spring scale at 6 RPM per minute. just aint gonna happen.
gears are gears,bearings are bearings, doesnt matter if its a muncie 4spd,a spicer rear axle or the headstock on a lablonde lathe.
they all have specific design properties to live by.
same bearing set in the input box on an SX is 9-14 inch pounds.
works ok.
I was in the first class of the XDP drive in chesapeake VA, during the course they tried to convince me that at reassembly the overall rolling torque from the lower drive shaft through the prop shaft should be 1.5inlbs.
thats 5 tapered roller bearings.
everyone in the class bought it but me.
I said ohhhh hell no.
finally the instructor got an engineer,almost non-english speaking, the engineer actually brought the engineering blue prints. yep seems the class training manual was way off. I knew this cause power transmission is power transmission and each tapered bearing needs a specific preload, usually something greater than 4 inlbs rolling and less than 15.
not enough and the rollers "bounc" on the race, to much and the bearing overheats and the rollers turn to sliders just before the unit desintergrates.
same as bevel gears or most gears in general. to deep a tooth contact and it overheats creating even deeper contact resulting in failure, to shallow and it tends to break off the crown. to far fwd and the toe fails,to far aft and the heel fails. to much backlash and it chatters causing failure, not enough lash and it overheats and fails.
but no I cant buy 5.25 plus or minus 0.
aint gonna happen in this life.
which is why with a dial indicator, a dial type inch pounds torque wrench and a tube of yellow lead marking paste I can assemble about any power transmission. its slow but very reliable.
the service manual is great, I try to follow it very closly, hiowever comon sense works well too.
if ya really wish to see something stupid look up setting the rolling torque on a jackshafted volvo intermediate housing .
a method I have never used,never will and even Volvo laughs at it, however its still in the manual.

 

[ziggy]

Re: Alpha 1 Gen II drive shaft bearing preload

Lets assume that I do have to replace the bearings. (Maybe for $80 it's cheap insurance). Looking on mercstuff.com I found this:

http://www.mercstuff.com/doublebearings.htm

part number: 0382.

thats the assy. but, myself, would not get glm parts. i got a shift shaft from them that i had to mod to get it to work. yer gonna trust them on brgs..... i'm not... get oem brgs. more like $145 or so if i remember right...

I have a very good bearing supplier near me that should be able to give me the correct ones.

Thoughts?

that must be yer local mercruiser dealer?

 

[rodbolt]

Re: Alpha 1 Gen II drive shaft bearing preload

changing the driveshaft bearings will nessesitate a checking/changing of the drive gear shimming.
unless the replacement bearings are diminsionally identical to the old ones, however production tolerances vary from bearing manufacturer to manufacturer.
goes back to gear tooth contact pattern and gear backlash.
to deep, it dies,to shollow it dies, to much lash it dies to little lash it still dies.

 

[tommays]

Re: Alpha 1 Gen II drive shaft bearing preload

What oil are you using on the bearings when you set them

 

[G1K]

Re: Alpha 1 Gen II drive shaft bearing preload

thats the assy. but, myself, would not get glm parts. i got a shift shaft from them that i had to mod to get it to work. yer gonna trust them on brgs..... i'm not... get oem brgs. more like $145 or so if i remember right...

that must be yer local mercruiser dealer?

no, buffalo bearing. I will use the dealer if BB does not have want.

changing the driveshaft bearings will nessesitate a checking/changing of the drive gear shimming.
unless the replacement bearings are diminsionally identical to the old ones, however production tolerances vary from bearing manufacturer to manufacturer.
goes back to gear tooth contact pattern and gear backlash.
to deep, it dies,to shollow it dies, to much lash it dies to little lash it still dies.

I have the two tools necessary for checking the alignment. Theoretically I would only need one, the one that you need to remove the top cap to use. The alignment of the vertical gear with respect to the housing did not change.

What oil are you using on the bearings when you set them

I am using a light coating of quicksilver high performance gear lube.

Ryan

 

[G1K]

Re: Alpha 1 Gen II drive shaft bearing preload

Just spoke to a couple people regarding the bearings.

For my bearing supplier (who will order these direct from Timken) $33.90 each for the bearings and $13.99 each for the cups.

The local mercruiser dealer: 1 bearing and cup asm: $133.50. He could not tell me if these are timken or not, they didn't have any in stock, but since this is a authorized merc dealer, I assume they would be.

Quite the price difference...

Hopefully when I press the bearings off this afternoon and take a very good look at the condition of the races and bearing roller surfaces, they will be okay. I will post up a high res picture of what I find.

Under my not so intense inspection, the bearings looked ok..

Ryan

 

[G1K]

Re: Alpha 1 Gen II drive shaft bearing preload

updating with pic of bearing cup. Has a little bluing and a peppering of specs. None of the specs are noticeably raised. I cleaned and re-oiled the bearings and they feel smooth as silk.

I have some other pics but this one came out the best.
Ryan

 

[ziggy]

Re: Alpha 1 Gen II drive shaft bearing preload

Has a little bluing and a peppering of specs.

mine looked about like yours, i couldn't decide which way to go. so i decided that my local merc mech made sense in his statement that he said he learned in merc. school. if theres any question about a brg., replace it.... i did.... yours, like mine, don't meet the criteria of no discoloation from overheating (blueing). their in question.....

i don't know if these new brgs. in my drive are the cause of this statement or not, but i suspect so. my drive used to be warm to the touch on the top cover, even just running it on the hose. let alone at the lake. i've put about 5 hrs on my new brgs. and so far, now, when i touch the top of my drive. it ain't warm at all. temps have been cool here, but temps were cool last fall prior to R&Rin the brgs too.... just my story though...

 

[Don S]

Re: Alpha 1 Gen II drive shaft bearing preload

Looks like time for new bearings to me. They will not roll smoothly for proper preload checks, and they will get hotter than normal once retorqued to specs.
If you have other bearings that look like that, they need replaced to.

It may not be what you want to hear, but it is what it is.

 

[G1K]

Re: Alpha 1 Gen II drive shaft bearing preload

2 new bearing/cup asm's on the way. I should be able to finally get this thing put back together this weekend.

Next task will be aligning the the engine.

Ryan