Slave: Internal or External? Which is better?

[SalahHH83]

HeavyChevy, yours in a 98, correct? That's how the line is on the newer 96+ GMT400s but on the older ones (mine is an 88), it is a threaded fitting. I might just have to bite the bullet and buy the newer MC with the proper hydraulic line. I have found these adapters

http://www.summitracing.com/parts/RUS-641001/):

via this thread on an LS1 tech forum http://ls1tech.com/forums/manual-transmission/1646317-help-gto-slave-cylinder-4an.html


I might just bite the bullet and buy the damn $106 MC... If I'm gonna be spending $21 for adapters and still need to get the hydraulic line, I wouldn't be saving a ton and would be risking having a system that does not work properly or could leak etc. It just really stinks to have to spend that extra money on a MC when my existing one works just fine

 

[heavychevy98]

Well I ordered the line from a 95 which was same as the one on my MC.

 

[SalahHH83]

So I am in the process of doing my NV4500 swap but I am having an issue with getting the internal slave to work. The clutch master cylinder for the internal slave attaches to the firewall differently than the MC that originally came on my 88. The original set up is the traditionally 2 studs which go through holes in the MC and are held on by nuts. The newer MC for the internal slave is an all plastic design that looks like it goes into the hole in the newer firewall and twists on.

Should I look for the entire pedal assembly from a 96+ truck and cut the firewall myself? Any help would be greatly appreciated

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[98_k1500]

Maybe those adapters were not such a bad idea...

 

[SalahHH83]

Maybe those adapters were not such a bad idea...

I think you're right... It's always the smallest things that make a swap like this difficult. Trying to make the square peg fit into the round hole.

 

[someotherguy]

I made the new style mc work on a '94 cab. Was a little bit of a chore but not terrible. The factory does it in a tricky way; the firewall is made up of like 2 or possibly 3 layers of sheetmetal bonded together. The hole for the mc is actually two holes of different sizes. The first hole which is larger, is really just a ledge of sorts for the gasket. What the mc is actually locking into is the bracket that attaches from inside the cab. So I just used a die grinder to slowly open up the hole that used to be for the old style mc, kept test-fitting the new one until it just barely made it through. That way there was still material left on the firewall to support the gasket and base of the mc. Then of course I marked and drilled the new bolt holes for the bracket.

Factory firewall setup for the new style mc:

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It's no big deal; just be sure you use a high quality grinder bit that is sharp. The more you work/heat the metal it will harden up on you and become a bear to grind.

Richard

 

[98_k1500]

I think you're right... It's always the smallest things that make a swap like this difficult. Trying to make the square peg fit into the round hole.

I'd take that mc back and get those adapters for the one you had.

 

[SalahHH83]

I made the new style mc work on a '94 cab. Was a little bit of a chore but not terrible. The factory does it in a tricky way; the firewall is made up of like 2 or possibly 3 layers of sheetmetal bonded together. The hole for the mc is actually two holes of different sizes. The first hole which is larger, is really just a ledge of sorts for the gasket. What the mc is actually locking into is the bracket that attaches from inside the cab. So I just used a die grinder to slowly open up the hole that used to be for the old style mc, kept test-fitting the new one until it just barely made it through. That way there was still material left on the firewall to support the gasket and base of the mc. Then of course I marked and drilled the new bolt holes for the bracket.

Factory firewall setup for the new style mc:

You must be registered for see images attach

It's no big deal; just be sure you use a high quality grinder bit that is sharp. The more you work/heat the metal it will harden up on you and become a bear to grind.

Richard

Thanks again Richard! You are the man! I ordered the adapters just in case but I am going to try to cut out the firewall with a dremel. I had the same concern with the multiple layers of the firewall but I'll follow your advice of keeping the steel cool as I cut.

I actually was trying to slide the NV4500 in yesterday and was having some trouble. I had adjusted the engine and the transmission jack to where they were pretty much lined up but I could not get the input shaft to go in smoothly. I am going to try to apply a small amount of grease to the splines and get some threaded rod to guide the tranny in tonight.

Thanks again! The picture was especially helpful

 

[someotherguy]

Not sure a Dremel is going to get the job done. I used a 1/4" die grinder on mine and ate up a lot of compressor time doing it. It's too bad you already have the hole for the old mc, or you could use a hole saw. Kind of tough using a hole saw on a pre-existing hole that is too large for a pilot bit...unless someone knows some hole saw tricks that I don't.

Richard

 

[SalahHH83]

Alright I've got a die grinder too. I just need to get some good cutting bits. I'll keep you updated! Thanks again.

Another quick question since you've done the swap yourself. I am trying to figure out what to do for the driveshaft. Mine is a 2WD and the stock transmission used a solid driveshaft with the slip on the transmission itself. On my NV4500 the rear output yolk is fixed, so I am going to need a center-slip driveshaft. I figure i'll go look at a local junkyard for one of suitable length and U joint size to match up with the SF 14 bolt I am swapping in, but any advice as to what trucks to look for with center slip driveshafts would be great