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1985 G20 mechanical to hydraulic clutch and Hydroboost discussion #733512
February 27th 2018 10:39 am
February 27th 2018 10:39 am
Joined: Sep 2013
Posts: 661
Indiana
tuner4life Offline OP
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tuner4life  Offline OP
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Joined: Sep 2013
Posts: 661
Indiana
I wasn't really sure where else to put this, but I'm on an information gathering mission right now.

The issue is the clutch in my 1985 G20 is all mechanical. There is a pedal, then pivot shaft, to a linkage pulling up, then to another pivot shaft that attaches to the frame on one end and the engine on the other end (because that's not sketchy at all), then another shaft that goes back and pushes on the clutch fork. As you can imagine, this is overly complicated and there are tons of joints and pivot points that are stressed hundreds of times during a drive. It's a system set up to fail. Not to mention the pedal is super heavy and doesn't really have a good "feel".

Ever since I first bought it, I have been trying to wrap my head around how best to to convert it to a hydraulic clutch, but as of yet, the hang up was where to mount the clutch master cylinder. There just isn't enough room on the firewall between the brake booster and the battery tray for any master cylinder to properly fit or the rod to get to the pedal. I couldn't figure out a good solution... Until the other day. I was browsing Facebook van groups and came across someone who was claiming to to be doing a manual swap in a G van and there were pictures showing a master cylinder (evidently from a pick-up or something) mounted very close to the hole for the brake booster (which was not installed at the time). Some comments later it was mentioned that the booster would occupy the same space as the Master cyl for the clutch. The op then said that there was no large vacuum booster because it was a Hydroboost setup. I was aware of what Hyrdoboost was, but has never given it a second look. I just figured it was a diesel thing and didn't apply to me. Well after a bit of research, I am intrigued to say the least. From what I am finding, our vans even came with it as a factory option on some models. Unfortunately I lost track of the FB post that had some of this info...

So... From the info I am finding, I can most likely convert the van to Hydroboost. I just need the booster unit, various hoses and "T"s, and the master cyl. The lines should be able to be plumbed into the existing steering system from what I'm finding, etc.. It sounds like this mod should result in better/easier braking, as well as freeing up valuable space for a proper hydraulic clutch master cylinder. Unfortunately that's where the good info ends..

I can't tell if I need to find a Hydrobooster specifically from a G van, or if others will fit and work. Supposedly they are all pretty similar as long as the vintage is close to correct, but I cannot find any info to confirm. Also, what about the master cyl? The vans have that special stepped master cyl to clear the hood. Not sure if I can re-use that, or if I need to find a different solution. Since supposedly some G vans came setup with Hyrdoboost, I should be able to find one. I don't know..

Anyways. That's what is banging around in my head now. However I do not have much experience with GM trucks, and literally zero experience with Hydroboost. It sounds great on paper, but what if any drawbacks are there? What should I know before diving into this head first? Most importantly, has anyone done this swap on a G van that would care to chime in?

worms
shift
cheers


[Linked Image]
1985 Chevy G20 305ci/4spd Manual
Re: 1985 G20 mechanical to hydraulic clutch and Hydroboost discussion [Re: tuner4life] #733518
February 27th 2018 2:23 pm
February 27th 2018 2:23 pm
Joined: Sep 2005
Posts: 8,339
Georgia, USA
CatFish Offline
carpal tunnel
CatFish  Offline
carpal tunnel
Joined: Sep 2005
Posts: 8,339
Georgia, USA
Our '95 G20 has hydro-boost from the factory.
I'll take some pics and look for an APO number if that'll help.
It supposedly has the trailer-tow package ordered by Sherry Conversions (T82??) but I've never researched it.


They can have my fried bologna sandwich when they pry it from my cold dead hands.
Re: 1985 G20 mechanical to hydraulic clutch and Hydroboost discussion [Re: tuner4life] #733521
February 27th 2018 3:27 pm
February 27th 2018 3:27 pm
Joined: Sep 2005
Posts: 8,339
Georgia, USA
CatFish Offline
carpal tunnel
CatFish  Offline
carpal tunnel
Joined: Sep 2005
Posts: 8,339
Georgia, USA
OK

It's a '95 G20 but that shouldn't make any difference.
Pardon the bright sun and phone pics.
Here's the hydro unit:
[Linked Image]

Closer:
[Linked Image]

The master cylinder:
[Linked Image]

And the space beside the unit you will need.....
[Linked Image]
The plastic there is covering the wiring pass-thru in the firewall. There might be another inch or so you could use if needed.

Just from looking I would say the brake lines will need to be rerouted to clear the clutch master but there is plenty of room. Might be tricky getting a battery in and out........
Our '93 G20 is vacuum boosted like our G1500 so I believe it was an option.
This help?

Last edited by CatFish; February 27th 2018 3:33 pm. Reason: kant spel

They can have my fried bologna sandwich when they pry it from my cold dead hands.
Re: 1985 G20 mechanical to hydraulic clutch and Hydroboost discussion [Re: tuner4life] #733528
February 27th 2018 5:34 pm
February 27th 2018 5:34 pm
Joined: Sep 2013
Posts: 661
Indiana
tuner4life Offline OP
addict
tuner4life  Offline OP
addict
Joined: Sep 2013
Posts: 661
Indiana
Catfish you rock! Thanks for the pics! I think I should be able to make it work fairly easily. All the parts seem to readily available, and making brake lines are no issue.

Last edited by tuner4life; February 27th 2018 5:35 pm.

[Linked Image]
1985 Chevy G20 305ci/4spd Manual
Re: 1985 G20 mechanical to hydraulic clutch and Hydroboost discussion [Re: tuner4life] #733534
February 28th 2018 7:48 am
February 28th 2018 7:48 am
Joined: Jun 2016
Posts: 32
Western Australia - Perth
G
Grey20 Offline
newbie
Grey20  Offline
newbie
G
Joined: Jun 2016
Posts: 32
Western Australia - Perth
Hi T4life,

Could you please let me know the model of your manual g/box ? I am fed up of my 700r4 fitted to my G20 used for towing.
Thanx in advance.

Re: 1985 G20 mechanical to hydraulic clutch and Hydroboost discussion [Re: tuner4life] #733536
February 28th 2018 8:38 am
February 28th 2018 8:38 am
Joined: Sep 2013
Posts: 661
Indiana
tuner4life Offline OP
addict
tuner4life  Offline OP
addict
Joined: Sep 2013
Posts: 661
Indiana
Hi Grey20. It's a 1985 G20 with a 305ci. The transmission is a NP833 4 speed overdrive. All original like that.

I do want to swap the trans to an old school bulletproof Muncie at some point because it's a direct swap, it's stronger. losing overdrive doesn't really matter to me since I am usually towing anyways.


[Linked Image]
1985 Chevy G20 305ci/4spd Manual
Re: 1985 G20 mechanical to hydraulic clutch and Hydroboost discussion [Re: tuner4life] #733582
March 02nd 2018 7:41 am
March 02nd 2018 7:41 am
Joined: Jun 2016
Posts: 32
Western Australia - Perth
G
Grey20 Offline
newbie
Grey20  Offline
newbie
G
Joined: Jun 2016
Posts: 32
Western Australia - Perth
Thanx for the info. I am thinking about doing a muncie too, but looking at the TKO as well.


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