When is shimming a lower unit required?

**racer** · 01-19-2020, 10:22 AM

OMC/Brp are not shimmed using the case as part of the process.

**Chaz** · 01-19-2020, 10:50 AM

Originally Posted by racer

OMC/Brp are not shimmed using the case as part of the process.

OK, I'll bite ..

So you shim both shafts on the bench, throw it in any case you find .. and you'll have perfect gear mesh. Is this what your saying ... ???

**Capt.Insane-o** · 01-19-2020, 11:14 AM

Omc cases only shim the pinion height. There is a bench fixture with different inserts per models

**H2OPERF** · 01-19-2020, 12:33 PM

Originally Posted by Chaz

OK, I'll bite ..

So you shim both shafts on the bench, throw it in any case you find .. and you'll have perfect gear mesh. Is this what your saying ... ???

Chaz I sense you are questioning OMCs ability to machine cases to a spec at +/- .0005 lol... Probably why many cases shizit gears and then do it again when a new gearset is installed, that is if they didn't just throw a gear set at it. I just did another 50 gearcase with the tool and felt confident enough it wasn't right to shim it by pattern.

**H2OPERF** · 01-19-2020, 12:48 PM

Hi tech tool, back face of pinion to top of timken race...

**Chaz** · 01-19-2020, 02:34 PM

I've done some Dana 60's and 12 bolt Chevies out of necessity. Never again ...

More 9" Fords than I can count. Even made my own pinion bearing spacers to replace the crush collar. (keeps from locking up the pinion support when you whack it with 1500 HP and 34.5x17" pencil erasers) Then you just read the number on the gear and shim the depth to axle center line. Bring the ring gear over till it has 0 to .004 clink-clunk and it's ready. I know the book says .010 , I say go screech in a set of big gum balls and check it , your lucky if it's only .010 ...

I bought about $1000 worth of new factory Merc tools and a manual, maybe 10 years ago. I don't know all the steps to skip, so I just follow the book. In the end, it still comes down to a long feeler blade and a flashlight , then a hose clamped flag ... LOL

I still paint em yella .. and give em a spin and a peek, before bendin the lil fold tab over. Old dogs new tricks ...

That OMC tool looks pretty hi-tech ...

Chaz = thinkin, ifin i ever try to relive my childhood by owning another 9.5 flat-top .. I'll horse trade, G-money or Kev, to go thru the lower ..

Come to think of It .. I had a 50 or 55 horse twin, about the time I started my motocross career in the early 70's. I drove that boat like I was at Amelia Earhart Park in Hialeah ... could not destroy that little ****** Lord knows I tried ..

**FUJIMO** · 01-19-2020, 02:43 PM

now I know who to bring my next nodular iron, or ''WAR'' 9'' to...

**Chaz** · 01-19-2020, 04:55 PM

If you build the pinion support right ... the single rib cases will last. They will only fit 28 and 31 spline axles though. Big bearing stuff will go 35 and aftermarket is needed to put gun-drilled 40's in ..

**racer** · 01-24-2020, 05:14 PM

Dave thats the old style tool and drive shaft but I know that you know that. One of the problems with the omc case is most of the time when they blow the gears out of them it warps the case making the alignment tool very important to check cases before rebuild.