Which year were hydraulic clutches introduced?

[RustySS]

I'm looking for some information on which year GM introduced the hydraulic clutch to replace the old mechanical style in C/K Trucks? I want to find a set of pedals, slave cylinder, clutch cylinder and bellhousing to upgrade my mechanical setup.

Thank you

 

[1987 GMC Jimmy]

1985

 

[marks86]

1985

ding ding ding we have a winner.

 

[1987 GMC Jimmy]

 

[RustySS]

Ah ha! Excellent. Now I just have to find a set of pedals and a bell housing. The clutch pedal return spring under the dash broke and I have not been able to find another one.

Would an aftermarket sheet metal bellhousing be the way to go if I had the choice? I have a mild 400 but not outrageous power and abuse.

 

[1987 GMC Jimmy]

Did you already find another square after the lemon you went and looked at, or did you already have one? Either way, if you're gonna do all this stuff, I'd use a cast iron bellhousing. Maybe an aluminum one would hold up and maybe it would crack. For the sake of longevity and not having to do it again, I would not.

 

[RustySS]

This is for my 1979 3/4 ton. Nothing fancy, just a really good run around truck. I have had it for 20 years now and I have never had a problem with it. I pulled out the transfer case and 4 speed to rebuild them because 3rd gear syncro was toast. Since I'm at the bellhousing, I might as well do the clutch.

 

[bluex]

Ah ha! Excellent. Now I just have to find a set of pedals and a bell housing. The clutch pedal return spring under the dash broke and I have not been able to find another one.

Would an aftermarket sheet metal bellhousing be the way to go if I had the choice? I have a mild 400 but not outrageous power and abuse.

Are you talking about the large one that goes on the pedal under the dash? I think I have one if you need it. I converted my mechanical pedals to hydraulic an didn't reuse it.

 

[CSFJ]

Did you already find another square after the lemon you went and looked at, or did you already have one? Either way, if you're gonna do all this stuff, I'd use a cast iron bellhousing. Maybe an aluminum one would hold up and maybe it would crack. For the sake of longevity and not having to do it again, I would not.

What applications came with a cast iron bellhousing? My hydro clutch set up came out of an '89 cab and chassis 1 ton, and that had the aluminum bell. Never seen an iron one myself.

 

[RustySS]

I've only ever seen 2 cast iron bellhousings. One is in my 1969 GMC Suburban, and the other one was on Ebay. I can't say for sure when GM switched to aluminum. I will do some more investigation.

@bluex - Yes, that big spring under the dash is the one. I attempted to install a new spring in the pedal assembly, but there was too much tension on it. I think I would like to go with a hydraulic clutch. I had issues with burning a clutch when I took it offroad for hunting. The frame flexed just enough to disengage the clutch slightly. The original body mount bushings were shot so I changed them out for poly-urethane bushings but it didn't help much.

 

[1987 GMC Jimmy]

It looks like the Action Line trucks got a cast iron SM465 bellhousing from the gearbox's inception in 1968 to 1972. I don't know if the earliest '73 model squares got one since they were also made in 1972. I didn't know that they switched to an aluminum bellhousing so early... I guess you'll probably be better off from an economy and time investment perspective going with the aluminum since the 1985 and on will have the slave mount on the bellhousing built in, but that still doesn't feel as right as a cast iron would for my taste. Maybe I'm just dumb and old fashioned. It looks like people have made the hydraulics work with the older cast iron bellhousings, but it'd take longer and be harder to find parts, I'm sure. I just googled "sm465 cast iron bellhousing hydraulic clutch." So I guess semi-my bad for thinking that the cast iron bellhousing went longer than it did.

 

[RustySS]

I have an aluminum bellhousing from a Corvette, however the center would have to be milled out to accept the larger input shaft bearing retainer of the SM465. I found it by pure luck at a swap meet for $80. I agree, I would feel more comfortable with a nodular cast iron bellhousing, but I'm not putting huge power through it so I will run an aluminum piece for the time being.

Although, the bellhousing that the NV4500 uses is beefed up and reinforced better in my opinion. It would be nice having an overdrive. It is from a 1993 3/4 ton so it would have the 6:34 (IIRC) 1st gear. Hmmm, what to do?

 

[1987 GMC Jimmy]

I have an aluminum bellhousing from a Corvette, however the center would have to be milled out to accept the larger input shaft bearing retainer of the SM465. I found it by pure luck at a swap meet for $80. I agree, I would feel more comfortable with a nodular cast iron bellhousing, but I'm not putting huge power through it so I will run an aluminum piece for the time being.

Although, the bellhousing that the NV4500 uses is beefed up and reinforced better in my opinion. It would be nice having an overdrive. It is from a 1993 3/4 ton so it would have the 6:34 (IIRC) 1st gear. Hmmm, what to do?

I think that'd be cool. You prefer a hydraulic clutch, and that's what you'd get with the New Venture. It's a more modern gearbox. That's what I'd do. The Saginaw Muncie is tough as hell, but if I ever wanted to take it out on the highway, I'd want the NV4500. Also, I'm guessing you've seen it and the truck that it came out of, but if not and you get it, make sure it's the GM bolt pattern and not the Dodge.

 

[bluex]

I've only ever seen 2 cast iron bellhousings. One is in my 1969 GMC Suburban, and the other one was on Ebay. I can't say for sure when GM switched to aluminum. I will do some more investigation.

@bluex - Yes, that big spring under the dash is the one. I attempted to install a new spring in the pedal assembly, but there was too much tension on it. I think I would like to go with a hydraulic clutch. I had issues with burning a clutch when I took it offroad for hunting. The frame flexed just enough to disengage the clutch slightly. The original body mount bushings were shot so I changed them out for poly-urethane bushings but it didn't help much.

Ok, I'm not going to use it so if you change your mind and need one just lmk.

 

[RustySS]

I managed to find another pedal return spring. I had a difficult time fighting with installing it on the pedal assembly. I wised up and used a heavy washer on one end so I could get a good pull on it. I bolted the pedal assembly to my work bench and used the porta-power hydraulic puller to install the other end. Cut the washer off with a zip disc and we are back in business.