350 swap, clutch issues

[TheGr8Doughboy]

I've cross posted this from the 60's forum, most of the 350 guys over there seem to be running auto trannys.

I'm totally out of money for my swap and trying to get down to GSMTR. It'll shift up, but not down unless stopped.

I'm running a motor out of a 1981 truck, bellhousing out of a 1975 truck, clutch for a 1981, clutch for for I think 1981, but the parts guys at the autoparts store said they were all the same (not quite correct according to the chevy dealership).

I think I've narrowed down my shifting, well lack thereof, problem to the chevy clutch assembly. Do any of you guys running the Chevy clutch with Toy hydrolic assembly remember what years parts you have? The Chevy dealership said that Chevy made only mechanical linkage clutches untill 1991. I'm thinking that the clutch fork is giving my slave cylinder too much mechanical advantage and not enough throw.


Thanks
Chris

 

[ridgerunner]

I don't have a lot of experience with this but I do have a question-

What kind of bracket did you use for the slave? The AA clutch bracket is kinda puny, make sure that it isn't moving (The one I made for my 350->ranger flexed until I beefed the hell out of it). My slave mount would flex so bad to the point that it wouldn't effectively disengage the clutch. My setup was AL bellhosuing, 168 tooth flywheel, Luk clutch, years unknown. Previously, I had run a AA adapter bellhousng to a h42.

 

[pbgbottle]

start with pressure plate .to use the chevy stuff you need a low profile diaphram, pressure plate . type like this one .check the list for years see link

http://www.historyofcars-c.com/items/7950337849.html

part #CA5473


i use the stock hydraulic setup . works for me using chevy low profile pressure plate chevy clutch disc t.o. and cast chevy fork . not stamped steel one . if using aluminum bellhousing use toyota bearing and toyota fork .

this worked for me .

 

[Gumby]

I have the Downey p-plate they sell for just this issue. I switched to an auto tranny so I can sell the p-plate. They charged me $275, but I have no use for it. make me an offer.

You can also try some things to get more travel. An early brake master is supposed to work. A bigger bore clutch master might work as well.

 

[theo]

I've been using the stock '69 GM clutch parts ('69 350, '69 sm465) with the '76 LC slave and master and the AA slave bracket. The clutch fork is the cast one. I had heard also that the stamped steel fork wouldn't work. I have just enough travel to completely disengage.

 

[Planet_X]

This one uses AA bracket to attach Toyota Slave cylinder and you can see the chevy 'cast iron' fork, and the jerry rigged return spring. SBC/early bellhousing/sm420.

 

[Rice]

This one uses AA bracket to attach Toyota Slave cylinder and you can see the chevy 'cast iron' fork, and the jerry rigged return spring. SBC/early bellhousing/sm420.

You're using the same housing/fork/slave/bracket setup I am (except for that spring thing). I use stock master cylinder and centerforce PP and clutch and the release is perfect. I have 2 questions .... are you sure you bled all the air out of the system and did you get the T/O bearing up close enough to the PP fingers? Over in the 60 section you said the T/O bearing was 0.250 away from the fingers.

 

[TheGr8Doughboy]

The AA bracket Sucked big time and the slave cylinder wouldn't even line up with the stamped steel clutch fork so I made my own out of 1/4" steel I had laying around it's flex is WAY less than the AA adapter and acceptable I think.

I do not have the funds or time to replace any major parts before GSMTR, I will look into a new pressure plate if this continues to be a problem.

I'm 99% sure that it clutch is bled. I had a friend of mine help me do it, he runs his own shade tree shop for drap cars so I figure he's pretty knowlegable.

I'm going to try to line up a cast fork and if that doesn't cut it look into a large bore master cylinder.

Thanks for the help I'll post up with my fix.
Chris

 

[theo]

Just a quick note on bleeding. I had to unbolt the slave and hold it with the bleeder up to get all the air out. Couldn't get it any other way.

 

[TonkaC]

What kind of bracket did you use for the slave?

I just used a metal plate and I believe another piece at an angle for another bolt. It is dark out so I couldn't get a better picture... no flashlight with a battery I'll try and get a better one tomorrow

EDIT: I got better pics of my setup. I do have to remove the slave from the bracket to bleed it correctly, but works for me.

 

[ranger]

I've been using the stock '69 GM clutch parts ('69 350, '69 sm465) with the '76 LC slave and master and the AA slave bracket. The clutch fork is the cast one. I had heard also that the stamped steel fork wouldn't work. I have just enough travel to completely disengage.

I used the AA bracket and a stamped arm. I had to shim the top of the bracket away from the top of the bellhousing and redrill and tap the holes so the slave cyl would line up with the fork. Also had to cut down the push rod so I had the proper throw. It can be done, but if you have the straight cast arm its a hell of alot easier.

 

[Ponce]

Wow, I using the AA slave bracket on my 350 to Ranger OD and never had a flexing problem. I got my clutch from napa part #MU5473-1B I think, the reciept is a little faded. The fork is cast that I got from the junk yard, came from a 78 truck. The slave is a new Toyota one that I had replace on my 2f before I did the conversion.
HTH

 

[TheGr8Doughboy]

theo- How would you bleed the slave cylinder after it was unbolted? I'm thinking about tryin to take it to a shop and have them hook up the auto bleeder deal, just so I know it's bled properly.

pbgbottle- I'm running Aluminum bellhousing. You're saying if I keep my clutch I can use the toyota fork?

Again, I don't have time to pull the transmission and get to the clutch itself. I'm hoping that I can pull the clutch fork without to much trouble.

Thanks again for more help here
Chris

 

[Bennett]

You do not have enough throw on you slave... Been there done that for 6 months.

I tried a number of suggestions with no success until I mounted a pre 69 brake master instead of the stock clutch master.
Mark Whatley from LCML told me to try it.
It works awsome..
The pre 69 brake master is 1" bore and the slave is under that ( 3/4" IIRC)..... thus more movement by nealy 5/8" for me or 25% more. The pedal is a *little* stiffer but works absolutely perfect.
I actually had too much movement and needed to adjust my slutch slave rod down The Master bolts right on in 2 miuntes ... hooked up and bled and shazam.. great clutch movement.

By the way.. in plantex pic he has his slave mounted upside down.. hard to bleed with the bleeder down.. I'd make sure yours is on top.

my similar troubles..https://forum.ih8mud.com/showthread.php?t=24851

 

[Planet_X]

By the way.. in plantex pic he has his slave mounted upside down.. hard to bleed with the bleeder down.. I'd make sure yours is on top.

my similar troubles..https://forum.ih8mud.com/showthread.php?t=24851

Yeah, good catch; you know I swapped this tranny so long ago I cant remember if it was just a mistake ; or done on purpose, I do remember having some trouble with the AA bracket not lining up with the Slave...

Note: at least for myself, bleeding the clutch really seems a non-issue as long as your not trying to do the job solo... now bleeding the brakes is an interesting chore..

 

[pbgbottle]

Chris .
just from reading downey off road v8 instruction manual . and advanced adapters manual .
if your aluminum bellhousing is from one of these suppliers . the instructions says that the conversion requires use of stock slave cylinder ,shift fork ,shift fork pivot ball,throw out bearing retainer .downey says their pivot ball is in a specail location to add more trvel to the t.o. bearing ,these conversions can use there clutch kit or any low cone diaphram pressure plate
advanced adapter pretty much the same accept they recommend the centerforce pressure plate . .

 

[theo]

theo- How would you bleed the slave cylinder after it was unbolted? I'm thinking about tryin to take it to a shop and have them hook up the auto bleeder deal, just so I know it's bled properly.

As noted, the stock slave was designed to be mounted on the passenger side. When you move it to the driver's side the bleeder is down and air (theoretically) can be trapped. I unbolt mine and hold it so the bleeder is up, then bleed it. Takes 3 hands and 4 feet!

 

[TheGr8Doughboy]

Yeah, my bleed screw is on top and the line is shortened to get the air out. My aluminum bellhousing is from the junkyard, $30 with a flywheel.

Bennett- Should I worry about over extending the slave cylinder? that was my initial hesitation in doning a swap such as that.

Aside from that, interesting devlopment. I parked the truck for about a week. Drove it last night and it down shifted, and upshifted just fine. Really weird it has not done this in the last 1000 mile I drove it. I didn't do anything to it. Only thing that changed was the outside temperature rose to a sweltering 75*. Is this telling me that it's not bled properly?

Thanks for the help guys

Chris

 

[Planet_X]

I would be checking out the motor and tranny mounts along with the rest of the fasteners that clamp your drivetrain parts together.

ie. motor to bellhousing/bellhousing to tranny/tranny to adapter/transfercase.

just a thought.

 

[Gumby]

Aside from that, interesting devlopment. I parked the truck for about a week. Drove it last night and it down shifted, and upshifted just fine. Really weird it has not done this in the last 1000 mile I drove it. I didn't do anything to it. Only thing that changed was the outside temperature rose to a sweltering 75*. Is this telling me that it's not bled properly?



Chris

Could very well be.