GMT 400 Hydroboost swap

[davkenrem]

Great info guys. I scored a HydroBoost system from a 2005 Z71 Suburban today. Got the booster, master cylinder all lines, stainless steel lines from Master Cyl to Proportioning valve. I cut the output lines on the bottom of the PV. Also got an after market oil cooler all for $50.00. HB and master look very good, truck was surprisingly clean.

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Question, I just finished installing a 9.5" 14b SF axle with Dual Piston Disc brakes from a 2002 Suburban on to my 97 K1500 Suburban. Would this PV provide the correct bias for the new 4 wheel disc I now have?

Still gotta get a pedal, and a push rod.

Was gonna grab the power steering pump but the cap was off and was full of water and fluid. I'll buy a new one.

This past week installed the hydroboost brake booster, master cylinder and pedal.


Here are the pedals, the hydroboost pedal is on the right. Not the step at the bottom of the post for the push rod, more on that in a second.

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Here is the pedal installed, it came from a 1996 C2500 diesel.

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My Hydroboost came from a 2005 K1500 Suburban Z71 and the push rod was to short. While I was in the yard, I searched around for a GMT 400 with the Vacuum booster already out, I found one and cut off the pushrod as log as I could.

I measured the pushrod from my vacuum booster from the mounting flange to the center of the pushrod ring and it was 7 ". I cut the Hydro booster rod off and threaded it and then marked the spare rod I got from the yard at 7" inches and cut it off. Attempted to thead them both. They are 2 different size. I ended up using a 3/8" rod coupling for the GMT400 side of the rod then tapped the other side for 7/16" for the GMT800 side.

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The step on the pedal post, it is larger on the Hydro pedal than on the Vacuum pedal. I had to drill it out to fit.

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the Brake switch fits fine.

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[davkenrem]

Here is a view of the hole that must be drilled for the GMT800 Hydrobooster to fit.

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Engine bay view.

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Need to get the proper power steering pump to finish up.

 

[Blklgt]

Looks great man!

 

[davkenrem]

Looks great man!

Thanks!!

 

[Brody]

Quick question re the hydroboost. I'm in Australia, and there aren't many of these trucks around...

Is there a bush which fits between the brake pedal pin and the hydroboost push rod?

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There is about 2mm of clearance between the brake pedal pin and the pushrod as pictured.

I came across a GMPARTS diagram which lists a bush under GM 14046812, however I do not have any diagrams which show it in situe so I can only assume that it is for the mount pin for the pedal to the bracket.

Really appreciate the help.

 

[davkenrem]

Quick question re the hydroboost. I'm in Australia, and there aren't many of these trucks around...

Is there a bush which fits between the brake pedal pin and the hydroboost push rod?

You must be registered for see images attach

You must be registered for see images attach

There is about 2mm of clearance between the brake pedal pin and the pushrod as pictured.

I came across a GMPARTS diagram which lists a bush under GM 14046812, however I do not have any diagrams which show it in situe so I can only assume that it is for the mount pin for the pedal to the bracket.

Really appreciate the help.

Need some more info:

What year is you truck? What year brake pedal did you get? are you using a GMT400 or GMT 800 Hydroboost.

My vehicle is a 97 K1500. The Pedal came from a 96 C3500. The Hydroboost came from a 2005 z71 Suburban (GMT800).


I installed a GMT400 ring on the GMT800 booster.

The stud on the GMT400 Hydroboost pedal has a stud with a shoulder at the base and is larger than the stud on the GMT400 Vacuum booster. I had to drill out the ring I welded on.

Welding on the ring was necessary because I was using the GMT800 booster and the rod length is too short on the for the GMT400.

I'm sure if your if your using a GMT400 pedal and booster it should all work. The vacuum pedal will not work with either the GMT400 or GMT 800 hydroboost. Note the location of the stud in my photo above.

 

[Brody]

Hey mate, thanks for the reply.

I've got a 1998 GMC Sierra 3500 Reg Cab (131.5" WB, 55.9" CA). GMT400.

It is fitted from factory with the Hydroboost, and in Australia they were converted to right hand drive and used as Ambulances here between 1996ish - 2000 or so. It since is back to a pickup truck (it has a bed, and not a Ambulance utility pod).

I thought to ask here, since you have done retrofits, I was curious to know if there was a bush between the pedal stud and and the Hydroboost push rod "O". Or is there simply stud in the pushrod "O" as pictured?

As photographed above, the pedal will creep slightly due to the clearance between Hydroboost push rod "O" being 2mm larger in diameter than the pedal stud. Just making sure.

Thanks again,

 

[Brody]

Tried a different GM Parts diagram library.

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PART 004 GM 14046812

BUSHING. Brake Pedal. Engine Clutch Pedal.
BUSHING,BRK PED PIV. Required: 02
For: G1,2,3 (1996-2002) (1996 - 2002).

https://www.wholesalegmpartsonline.com/showAssembly.aspx?ukey_assembly=382232&ukey_product=2684685

Is for the pedal pivot bush only, not what I had first assumed was a bush for the pedal stud.

So, I'm guessing that there is no bush between the Hydroboost push rod "O" and the pedal stud. There must be a bit of free play desired? I've not seen any clearance on any other vehicle before.

I'm stumped. I know its 2mm of clearance, but still.

 

[davkenrem]

Tried a different GM Parts diagram library.

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PART 004 GM 14046812

BUSHING. Brake Pedal. Engine Clutch Pedal.
BUSHING,BRK PED PIV. Required: 02
For: G1,2,3 (1996-2002) (1996 - 2002).

https://www.wholesalegmpartsonline.com/showAssembly.aspx?ukey_assembly=382232&ukey_product=2684685

Is for the pedal pivot bush only, not what I had first assumed was a bush for the pedal stud.

So, I'm guessing that there is no bush between the Hydroboost push rod "O" and the pedal stud. There must be a bit of free play desired? I've not seen any clearance on any other vehicle before.

I'm stumped. I know its 2mm of clearance, but still.

Sorry, I was under the impression that you were doing a swap. I have only done this one swap myself but I have looked at allot vehicles in the wrecking when searching for parts and the pedal assembly I have came from a 96 C3500 and had no bushing, nor did any that I looked at. Does not mean that there isn't one. I looked at about 7 vehicles from 88-98 most were diesel, but several were gas. None that still had the pedal had a bushing.

 

[Brody]

Sorry, I was under the impression that you were doing a swap. I have only done this one swap myself but I have looked at allot vehicles in the wrecking when searching for parts and the pedal assembly I have came from a 96 C3500 and had no bushing, nor did any that I looked at. Does not mean that there isn't one. I looked at about 7 vehicles from 88-98 most were diesel, but several were gas. None that still had the pedal had a bushing.

Most likely isn’t one then!

I was just stumped that the 2 mm of clearance allows the pedal to move before contacting the push rod. Didn’t look right, but who knows, maybe it allows the brake switch to operate without engaging the brakes per se.

Thanks again, appreciate it!