Hydroboost: GMT400 to GMT800 swap *tutorial*

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92Raiderburban

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I did this swap recently, and on a *BUDGET*. While driving on Lake Mead Blvd up here in North L.V., I happened to spot a stripped-to-the-bone, fire damaged 99-06 pickup truck abandoned in an alley. Noticed it had 8 lugs so naturally looked in the engine bay and walla! Hydroboost still intact. Had been searching for a GMT400 HB nearby since mine on my '92 was already leaking when I bought the truck and recently started leaking more.

OK, now, to jump right in it. I did this swap in about 2 hours, takin' my time.
The first part of this I want to put out there is the '400 master cylinder. It bolts right up to the '800 HB. So no needing to buy the new master if your old one is still good.

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The PS lines are the same thread as you can see and also bolt right up without a problem.

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Three (3x) studs bolt up to the original mount holes on the firewall. I went lazy on this (was in no mood to drill another hole) and knocked the 4 one completely out. The unit isnt loose or wobbly when I put my foot on the pedal.
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Lastly, but not least, is the pedal rod. Quite a few of these tutorials I ran across on other forums show the rod cut and rewelded. *No need for this*. The rod can be removed via tool made to press against the crimped metal housing where the ball is snug in. Pull both rods from both units and swap the '400 rod into the '800 HB unit. Once you bolt it in via the studs, the geometry is spot on with the factory GMT400 brake pedal.
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Thats it! Done. Fill up the power steering pump and take her for a cruise to test it out
 

pgutier1

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97MexVortec, question please...I have a '92 K1500 4wd Suburban and will be doing the brake swap to NBS calipers and rotors. Is the HB better than vaccum and would you recommend the swap to HB as well? If you do recommend the swap would you stay with the '92-'94 HB or would the HB up to '99 work as well? What are you thoughts?
 

92Raiderburban

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97MexVortec, question please...I have a '92 K1500 4wd Suburban and will be doing the brake swap to NBS calipers and rotors. Is the HB better than vaccum and would you recommend the swap to HB as well? If you do recommend the swap would you stay with the '92-'94 HB or would the HB up to '99 work as well? What are you thoughts?
Yes the Hydroboost compared to vacuum is day and night difference. You will need a HB power steering pump with extra ports to plumb in. It is definitely superior in stopping power. Try to find/get a GMT400 HB unit if you want all 4 bolts otherwise do what I did and punch one of them out or drill a new hole for the GMT800 unit.
 

pgutier1

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Lastly, but not least, is the pedal rod. Quite a few of these tutorials I ran across on other forums show the rod cut and rewelded. *No need for this*. The rod can be removed via tool made to press against the crimped metal housing where the ball is snug in. Pull both rods from both units and swap the '400 rod into the '800 HB unit. Once you bolt it in via the studs, the geometry is spot on with the factory GMT400 brake pedal.
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Thank you for the previous response. Please explain which "tool" I might need to press the rods out? Any information would be appreciated!

I decided to go with the 800GMT HB unit, since I'm going with NBS brakes.
 
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