Re-siliconing a Muncie

Atilla the Fun · Post by **Atilla the Fun** » Thu Oct 30, 2008 1:46 pm

On a whim yesterday, I disassembled my higher-mileage Munchy, to find out what gearing it has, and to retrieve the speedometer driven gear. Blue, with 30 teeth, by the way.
I cleaned everything up, opened a new tube of Permatex RTV, which came out brown. I followed the instructions on the packaging, and didn't tighten any bolts. I left them just touching, not even snug, but all the way in.
So I went back out 2 hours later to tighten them, and every one is a turn loose! Not knowing what happened, I tightened them all.
And by the way, the final is 4.095238:1, from a 21 tooth driving an 86 tooth, and the speedometer drive gear had 35 teeth.

Series8217 · Post by **Series8217** » Thu Oct 30, 2008 3:16 pm

Not sure what "re"siliconing is all about. The case never should have been siliconed in the first place.
The proper case sealant is Loctite 518 Anaerobic Sealant.

Boscolingus · Post by **Boscolingus** » Thu Oct 30, 2008 4:47 pm

several rebuilds myself, and I can confirm Series' information

Atilla the Fun · Post by **Atilla the Fun** » Thu Oct 30, 2008 5:21 pm

Thanks! That'll be good to know IF this doesn't work, but what I found was silicone.

Series8217 · Post by **Series8217** » Thu Oct 30, 2008 6:18 pm

Well, if that doesn't work you may not have a transmission to try it again on.

Anything between the case halves besides a gap-filling sealant such as specified by GM can deform the case and/or space out the case halves --- especially with the way you were trying to do it, since it sounds like you were actually trying to get the silicone to set before cranking it down.
There must be no gasket there; that includes a thin layer of silicone. Loctite 518 just fills in the tool marks between the aluminum surfaces; it's basically sealing aluminum-on-aluminum.

You are decreasing your bearing preload by the amount your silicone is taking up. All of the shafts on the Muncie use tapered roller bearings; the preload must be set precisely as specified for that transmission or it will suffer premature failure.

Do it right the first time...

Atilla the Fun · Post by **Atilla the Fun** » Fri Oct 31, 2008 11:09 am

The trans has to come back out anyway, but I needed a way to support the inner ends of the axles so I could roll the car around back for the winter. I think I need to drill and tap the thing for larger bolts, as it seems the PO overtightened some bolts, I think some are about stripped out. Too bad I sold my original Muncie, but this one only has to get me 10 miles to the fairgrounds on the morning of July 3rd, around the fairgrounds on the 3rd and 4th, and back out the gate on the evening of the 4th. If it fails after that, fine.
I have the 6-speed, and I'm gonna buy a second one to put the Quaife in. Then I can open up this first one for a custom taller first gear.