hydraulic clutch conversion issue - The 1947 - Present Chevrolet & GMC Truck Message Board Network

J1MMY · 05-02-2015, 03:42 AM

I have fitted a hydraulic pedal box out of an '85 (kindly supplied by a super helpful forum member

) and had shipped in a new master cylinder.

Went to fit it and the plunger rod for the master cylinder wants to sit the other side of the pedal from the mounting bar - to mount it on the bar is possible but will mean that the rod will be working on an angle. That can't be right!

The factory hole in the firewall had been previously used for the speedo cable but appears to be in practically the perfect place.

I have taken some pics from the firewall side and shown the master cyclinders also:

Ultimately, I will bend the bar if I have to!

Wrecked1982 · 05-02-2015, 10:08 AM

is your cab 85 and up?

J1MMY · 05-02-2015, 09:13 PM

The truck is, like many over here an ex- forces vehicle but it is registered off the vin of a '79 vehicle.

Wrecked1982 · 05-03-2015, 08:33 AM

because if its an earlier cab than 85(witch appears to be from the wipers area) ,the speedo cable hole probably inst the right location for the clutch master. also check if your pedals came from a hydro-boost or a vacuum brake as they are different.

bdiamond · 05-03-2015, 10:37 AM

There is a diagram online with measurements for the hole. I'll see if I still have it saved......I do... I'll upload it as soon as I get on photobucket

J1MMY · 05-03-2015, 12:44 PM

The pedal box came from a vacuum braked vehicle. I did think the conveniently placed speedo hole was almost too fortuitous! Thanks for the responses they're much appreciated.

bdiamond · 05-03-2015, 08:09 PM

http://67-72chevytrucks.com/vboard/s...d.php?t=551798

Check post #17. He says he will email a PDF template. I never could get logged on to Photobucket. I have a template I can email if you'll send an address.

MalibuSSwagon · 05-03-2015, 09:26 PM

An 85 and newer cab will be dimpled with the locations of the master cylinder bolts.

jetmech85 · 05-03-2015, 11:53 PM

If this helps, each master cylinder bolt has a rod behind the firewall that braces the master cylinder to the pedal assy.

J1MMY · 05-11-2015, 05:15 PM

Quote:

Originally Posted by jetmech85

If this helps, each master cylinder bolt has a rod behind the firewall that braces the master cylinder to the pedal assy.

I have been scratching my head over this - although they came with the assembly they'd been removed and I can only guess that they go either side of the bolt that pins the clutch pedal into the assembly.

Also having read the other thread in the link, the assembly used there (and templated from) was hydro not vacuum. I wonder how different the locations of the hole would be?

**1774btcrew** · 05-11-2015, 09:21 PM

It doesn't matter if the pedal assembly is hydroboost or vacuum boost. The clutch master cylinder mounts in the same place. The differences between the two pedal assemblies have nothing to do with the clutch pedal and the mounting of the clutch master cylinder.

jetmech85 · 05-11-2015, 11:49 PM

J1MMY, I can get you pics of what ever you need. I have a vac boost, hyd. clutch 3/4 ton. Also a hydro boost 1 ton but it is automatic. I just have to email them to you because I'm too dumb to get them from iphone to computer. Just PM me with what you need and maybe you can post here for all to see. On my '85 the speedo cable comes through the firewall right next to the cylinder.

05-02-2015, 10:08 AM	#2
Wrecked1982 Registered User Join Date: Feb 2011 Location: Cold Canada Posts: 310	Re: hydraulic clutch conversion issue is your cab 85 and up? __________________ 1981 c30 dually, 350 sm465 ex tow truck now yard mule 1985 k35 dually, 454 th400 np205 1985 D30 cucv M1008, 6.2 th400 np208 1999 toyota tacoma, lifted 6'' 31'' tires 2003 toyota echo, reliable and damn cheap on gaz

05-02-2015, 09:13 PM	#3
J1MMY Registered User Join Date: Aug 2009 Location: Wiltshire, UK Posts: 157	Re: hydraulic clutch conversion issue The truck is, like many over here an ex- forces vehicle but it is registered off the vin of a '79 vehicle. __________________ '63 C10 Longbox fleetside '94 C1500 Sierra ex-USAF beater

05-03-2015, 08:33 AM	#4
Wrecked1982 Registered User Join Date: Feb 2011 Location: Cold Canada Posts: 310	Re: hydraulic clutch conversion issue because if its an earlier cab than 85(witch appears to be from the wipers area) ,the speedo cable hole probably inst the right location for the clutch master. also check if your pedals came from a hydro-boost or a vacuum brake as they are different. __________________ 1981 c30 dually, 350 sm465 ex tow truck now yard mule 1985 k35 dually, 454 th400 np205 1985 D30 cucv M1008, 6.2 th400 np208 1999 toyota tacoma, lifted 6'' 31'' tires 2003 toyota echo, reliable and damn cheap on gaz

05-03-2015, 10:37 AM	#5
bdiamond Registered User Join Date: Sep 2007 Location: Wichita Falls, Texas Posts: 459	Re: hydraulic clutch conversion issue There is a diagram online with measurements for the hole. I'll see if I still have it saved......I do... I'll upload it as soon as I get on photobucket

05-03-2015, 12:44 PM	#6
J1MMY Registered User Join Date: Aug 2009 Location: Wiltshire, UK Posts: 157	Re: hydraulic clutch conversion issue The pedal box came from a vacuum braked vehicle. I did think the conveniently placed speedo hole was almost too fortuitous! Thanks for the responses they're much appreciated. __________________ '63 C10 Longbox fleetside '94 C1500 Sierra ex-USAF beater

05-02-2015, 03:42 AM	#1
J1MMY Registered User Join Date: Aug 2009 Location: Wiltshire, UK Posts: 157	hydraulic clutch conversion issue I have fitted a hydraulic pedal box out of an '85 (kindly supplied by a super helpful forum member ) and had shipped in a new master cylinder. Went to fit it and the plunger rod for the master cylinder wants to sit the other side of the pedal from the mounting bar - to mount it on the bar is possible but will mean that the rod will be working on an angle. That can't be right! The factory hole in the firewall had been previously used for the speedo cable but appears to be in practically the perfect place. I have taken some pics from the firewall side and shown the master cyclinders also: Ultimately, I will bend the bar if I have to! __________________ '63 C10 Longbox fleetside '94 C1500 Sierra ex-USAF beater

05-03-2015, 08:09 PM	#7
bdiamond Registered User Join Date: Sep 2007 Location: Wichita Falls, Texas Posts: 459	Re: hydraulic clutch conversion issue http://67-72chevytrucks.com/vboard/s...d.php?t=551798 Check post #17. He says he will email a PDF template. I never could get logged on to Photobucket. I have a template I can email if you'll send an address.

05-03-2015, 09:26 PM	#8
MalibuSSwagon Registered User Join Date: Sep 2009 Location: Weare,NH Posts: 1,592	Re: hydraulic clutch conversion issue An 85 and newer cab will be dimpled with the locations of the master cylinder bolts. __________________ Eric 1992 Oldsmobile Custom Cruiser 1986 Chevrolet C10\|5.3L\|TKO600\|Shortbed\|Custom Deluxe 1983 Malibu Wagon\|TPI 305\|T5 5 speed\|3.73 non-posi

05-03-2015, 11:53 PM	#9
jetmech85 Registered User Join Date: Sep 2014 Location: Texas Posts: 215	Re: hydraulic clutch conversion issue If this helps, each master cylinder bolt has a rod behind the firewall that braces the master cylinder to the pedal assy.

05-11-2015, 09:21 PM	#11
1774btcrew Senior Member Join Date: Jun 2009 Location: Phoenix AZ Posts: 4,603	Re: hydraulic clutch conversion issue It doesn't matter if the pedal assembly is hydroboost or vacuum boost. The clutch master cylinder mounts in the same place. The differences between the two pedal assemblies have nothing to do with the clutch pedal and the mounting of the clutch master cylinder. __________________ AZPartsLocators on Instagram 1972 Cheyenne Super Short Bed big block "Blackie" 1977 Crew Cab GMC Short bed with 4BT Intercooled Cummins Diesel and a 4L80e "The Junkyard Dog" 1985 Crew Cab Chevy dually with 5.9 Cummins "The Big Dog" This is what my dad liked to be called by the grandkids before he passed so it seems fitting for his old truck.

05-11-2015, 11:49 PM	#12
jetmech85 Registered User Join Date: Sep 2014 Location: Texas Posts: 215	Re: hydraulic clutch conversion issue J1MMY, I can get you pics of what ever you need. I have a vac boost, hyd. clutch 3/4 ton. Also a hydro boost 1 ton but it is automatic. I just have to email them to you because I'm too dumb to get them from iphone to computer. Just PM me with what you need and maybe you can post here for all to see. On my '85 the speedo cable comes through the firewall right next to the cylinder.



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