hydro clutch swap questions - The 1947 - Present Chevrolet & GMC Truck Message Board Network

qksilver · 09-05-2010, 09:59 PM

I am converting a 78 1/2 burb I just bought to a 3/4 ton. I was given a freshly wrecked 87 3/4 pick up. I checked things out and pretty much everything will be easy to swap.

My question is I want to replace the turbo 350 with the granny gear 4 speed from the 87. The actual parts swap except for the clutch master cylinder and manual pedal set up.

Will the manual pedal set up from the 87 bolt in place of the 78 auto?

How to mount the clutch master cylinder to the firewall? From what I can tell with out unbolting things is that the firewalls are different.

Anybody done this? any tips or advice?

Thanks,
Steve

D13 · 09-07-2010, 06:27 AM

TTT

I do know the later firewalls have dimples for the clutch cylinder.

I too would like to know if the pedals interchange on the mounting bracket.

78customdeluxe · 09-07-2010, 06:09 PM

This is going back 5 or 6 years since ive done this, but its fairly easy, even easier since you have the hydro truck cab with you. I dont know if the pedals will switch into the saddle, but I switched the whole assembly out. The holes are a little different size since the 78 was standard and the 80's were metric iirc, but i had to drill some either way. That saddle will have bolts going both ways through the firewall if you go that route and at least most of the bolts will also go though your brake booster mounting bolts. Just take measurements on where the master is bolted in relationship to the mounting bolts to the brake booster and you should be right there. If your going through all the work of changing this over, I would HIGHLY reccomend getting a new master and slave cylinder unless yours are in about mint shape. The last thing I would want is to get everything switched and bled only to have one go out a week later. By the way when you bleed it I dont do it with the whole thing in the truck, I put the master in the vice and pump it by hand because there are so many places for air to get trapped in the system. You'll know you have it when you cant move the rod on the master anymore, and trust me, you can get it in there all together, its the only way i'll bleed a hydraulic clutch on an older chevy.

bikes&bowties · 09-07-2010, 06:41 PM

I dont know if i am reading it all correctly but yes the clutch/brake pedal and hanger will bolt into where the brake pedal and hanger are right now

scruffre · 09-08-2010, 12:54 AM

I used a 87 set up in my 78 Blazer when I went from auto to standard. just had to pop the three holes in the firewall for the clutch cylinder

qksilver · 09-08-2010, 08:23 PM

Cool,
Thanks guys,
Steve

09-05-2010, 09:59 PM	#1
qksilver Senior Member Join Date: Dec 2004 Location: Southern Pines NC Posts: 3,853	hydro clutch swap questions I am converting a 78 1/2 burb I just bought to a 3/4 ton. I was given a freshly wrecked 87 3/4 pick up. I checked things out and pretty much everything will be easy to swap. My question is I want to replace the turbo 350 with the granny gear 4 speed from the 87. The actual parts swap except for the clutch master cylinder and manual pedal set up. Will the manual pedal set up from the 87 bolt in place of the 78 auto? How to mount the clutch master cylinder to the firewall? From what I can tell with out unbolting things is that the firewalls are different. Anybody done this? any tips or advice? Thanks, Steve

09-07-2010, 06:27 AM	#2
D13 Registered User Join Date: Feb 2007 Location: Memphis MI Posts: 1,851	Re: hydro clutch swap questions TTT I do know the later firewalls have dimples for the clutch cylinder. I too would like to know if the pedals interchange on the mounting bracket. __________________ 1987 2 ton 1982 250/TH350 beater in progress Dad's 1981 3/4 L6 3 on tree posi and no options, awaiting restoration or scrapping Plus a mess o' tractors

09-07-2010, 06:09 PM	#3
78customdeluxe Registered User Join Date: Dec 2002 Location: Upper Sandusky Ohio Posts: 72	Re: hydro clutch swap questions This is going back 5 or 6 years since ive done this, but its fairly easy, even easier since you have the hydro truck cab with you. I dont know if the pedals will switch into the saddle, but I switched the whole assembly out. The holes are a little different size since the 78 was standard and the 80's were metric iirc, but i had to drill some either way. That saddle will have bolts going both ways through the firewall if you go that route and at least most of the bolts will also go though your brake booster mounting bolts. Just take measurements on where the master is bolted in relationship to the mounting bolts to the brake booster and you should be right there. If your going through all the work of changing this over, I would HIGHLY reccomend getting a new master and slave cylinder unless yours are in about mint shape. The last thing I would want is to get everything switched and bled only to have one go out a week later. By the way when you bleed it I dont do it with the whole thing in the truck, I put the master in the vice and pump it by hand because there are so many places for air to get trapped in the system. You'll know you have it when you cant move the rod on the master anymore, and trust me, you can get it in there all together, its the only way i'll bleed a hydraulic clutch on an older chevy. __________________ 88 Crewcab Dually 5.9 Cummins, 5306 Eaton 6-speed, converted 4x4 w/52's up front, 90 front clip(parting out) 1986 ElCamino (needs motor) 1970 C30(future service truck for my ag-equipment repair business) 1970 CST10(parting out and partial donor for the '70 C30) 2000 GMC 1500 ext cab sb, z71, 5.3 loaded auto

09-07-2010, 06:41 PM	#4
bikes&bowties Registered User Join Date: May 2009 Location: Washington Posts: 663	Re: hydro clutch swap questions I dont know if i am reading it all correctly but yes the clutch/brake pedal and hanger will bolt into where the brake pedal and hanger are right now

09-08-2010, 12:54 AM	#5
scruffre Registered User Join Date: Apr 2009 Location: Carrying Place, Ontario Posts: 48	Re: hydro clutch swap questions I used a 87 set up in my 78 Blazer when I went from auto to standard. just had to pop the three holes in the firewall for the clutch cylinder __________________ Dave

09-08-2010, 08:23 PM	#6
qksilver Senior Member Join Date: Dec 2004 Location: Southern Pines NC Posts: 3,853	Re: hydro clutch swap questions Cool, Thanks guys, Steve



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