Outdrive guys, talk to me.

[Bubba1235]

Ok, so I have the manuals for the OMC Cobra and read through the proceedure for setting gear lash (after preloading the bearings) in the upper unit. What a PITA!!!

Can someone tell me why using plastic guage on these gears (clearance and backlash) doesn't work?

 

[HT32BSX115]

Re: Outdrive guys, talk to me.

Can someone tell me why using plastic guage on these gears (clearance and backlash) doesn't work?

[FONT=Arial, Helvetica, sans-serif]PLASTIGAUGE[/FONT] measures clearance. When you are setting a bearing "Preload" you have no clearance. BECAUSE of the preload....... the surfaces are in direct "contact" ....... there's no clearance to measure...


Plastiguage is used in "plain" bearings (bushings) where there is clearance in bearings lubricated with pressure oil (the pressure oil occupies the "gap").

Tapered roller bearing are usually not pressure lubricated and usually have no clearance.....hence....the "pre-load"


Regards,


Rick

 

[HT32BSX115]

Re: Outdrive guys, talk to me.

Well, maybe you did confuse me. I confuse easily.

I thought you asked:

Can someone tell me why using plastic guage on these gears (clearance and backlash) doesn't work?

I think I gave you an acceptable reason. There's no clearance on a pre-loaded bearing. (otherwise it wouldn't be "PRE-LOADED")


BUT! You said GEARS (Man I should read these posts more carefully!!!

Well that's different!!

It would sure be easier to use Plastiguage to do it if you could fiigger out a good way to get it in there.

I suspect that you can get a far more accurate measurement by doing it the hard way. as opposed to using plastigage and a mic.

 

[a70eliminator]

Re: Outdrive guys, talk to me.

Wouldn't the gearsets have a tendency to "scrub" the plastiguage as they mesh? or am i not understanding this, normally we use marking compound for contact pattern and indicate the backlash. But i'm not looking the manual nor have i ever dealt with this, other than the typical Ford 9" many many times.

 

[Don S]

Re: Outdrive guys, talk to me.

Backlash is the distance a gear tooth has between the other gears two teeth. From the front to back surface at exactly one certain point on that gear. With a dial indicator you measure that gap, or with some tabs you attach to a shaft you measure a calculated gap.
Plastigage, on the other hand tells you nothing but the distance between a crankshaft and a bearing and gives you what the gap is by how much it is mashed.

You need to do the dial indicator thing on back lash, it's the only way to get accurate dimensions

 

[a70eliminator]

Re: Outdrive guys, talk to me.

On a typical ring and pinion you set pinion depth to get acceptable tooth contact pattern, you then bring the ring gear into the pinion to achieve backlash, each adjustment effects the other so there is no peticular order as long as you end up with accepatable contact and backlash you'll be good.

I'm just speaking out with my experience in setting up differentials and have absolutely 0 experience with my outdrive gears but I do understand the theory of what needs to happen. It sounds like you have the upper hand on it, but the plastigauge technique is questionable.

 

[Don S]

Re: Outdrive guys, talk to me.

On a typical ring and pinion you set pinion depth to get acceptable tooth contact pattern, you then bring the ring gear into the pinion to achieve backlash, each adjustment effects the other so there is no peticular order as long as you end up with accepatable contact and backlash you'll be good.

That's not how it's done on outdrives. Preload, backlash, then gear pattern (on Volvo) Merc doesn't use gear patterns, just special tools to set gear heights that supposedly get the proper pattern. Then backlash check which should be within specs with proper gear heights. Just a double check.
I'm thinking he actually has a Volvo SX drive he is working on, after reading his other post.

 

[Don S]

Re: Outdrive guys, talk to me.

You can't use Plastigauge like that ...... PERIOD............
Just won't work. Think about it. You can make your tests work out any way you want them. But you can't put a non turning pressure that means anything on the PG to tell you anything.
But have fun trying.