Brake problem not holding

97rada

97rada

New member
My race truck is not holding on the brakes. It's a 94 with a hydroboost conversion, new napa power steering pump and I have swapped a known good booster in and still can't hold 25 psi well. When you pump up the brakes with the truck off it has great pedal. Start it and pedal doesn't kick back like it should. It also doesn't have nearly as strong of a pedal as I feel it should with the truck running. Kinda wanting to blame the 50 dollar napa pump. Anyone have any ideas?? I will say I havnt pulled the rear brakes apart yet to inspect but don't think that's the problem.
 
I was in this same situation when I trailered the truck to Seattle to race after changing the front brakes the week before. Felt like there was air in the line. Bled them 3 more times. Put a whole bottle of new fluid through it. No dice. Did some reading, grabbed a flat head screw driver and manually ratcheted over the rear adjusters through the little access hole. Went until I barely felt friction when rotating the tire with the rear end on the jack. Then backed off one click. Felt amazing ever since!
 
I had a similar problem with mine, what fixed it was taking off the antilock valve or whatever it's called and found a coupler to just hook the lines direct. But I think I remember you saying you already did that. I also run a vacume booster, will hold 40psi no problem.
 
Red Sleeper said:
Before you throw another pump at it, why not pull the rear drums off and do an inspection?
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I plan to pull them apart this weekend and see what condition it's in. Just don't want to leave that as my only possibility when it needs to be loaded in the trailer ready to race after next weekend. I suppose that could very easily be the issue though.
 
Also while you have them torn apart, I think you can buy a wheel cylinder from a chevrolet, believe those are the largest diameter available.
 
zstroken said:
Also while you have them torn apart, I think you can buy a wheel cylinder from a chevrolet, believe those are the largest diameter available.
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Was just getting ready to say this. I have one ton chevy wheel cylinders in my dually and the difference is amazing. Definitely the way to go if you're not swapping to disc brake rear yet.
 
kxhonda said:
Was just getting ready to say this. I have one ton chevy wheel cylinders in my dually and the difference is amazing. Definitely the way to go if you're not swapping to disc brake rear yet.
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This is just to get me through the last 2 races it's getting discs this winter when I have more time.
 
3500 front calipers will swap right in place of the 2500 calipers (front). They have a larger diameter piston than the stock 2500 calipers. Every little bit helps. This should also apply if using stock parts on rear disc conversion. Little bit of research should tell if compatible.
 
f6jbob said:
3500 front calipers will swap right in place of the 2500 calipers (front). They have a larger diameter piston than the stock 2500 calipers. Every little bit helps. This should also apply if using stock parts on rear disc conversion. Little bit of research should tell if compatible.
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Good info, I didn't know that one. My rear kit is going to be very generic and use mostly front end parts if I can. We shall see when the time comes.
 
Takes less than 5 minutes to adjust those drums through the access hole... I didn't care to take mine apart and inspect the pads as I will also be going disc soon.
 
If you replace the rear wheel cylinders, tell them you want a set for a 1994 Chevy 3500 dually, that model is the larger diameter bore wheel cyl and a direct replacement.
 
f6jbob said:
3500 front calipers will swap right in place of the 2500 calipers (front). They have a larger diameter piston than the stock 2500 calipers. Every little bit helps. This should also apply if using stock parts on rear disc conversion. Little bit of research should tell if compatible.
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If it has the 8800lb Dana 60 (which it does unless swapped) it will already have the larger bore calipers.
 
Rear wheel cylinder part number is 37337, these make a HUGE difference and will definitely let you hold more boost on the launch. They are cheap as well, like $8 to $12 per cylinder depending on brand name or supplier. I can hold 20 psi launch on the rear tires with a good firm stab on the brake pedal. Before it would start to push through the rear brakes on my 2wd around 7 psi boost. On a 4x4 truck with contribution from the front brakes, I'll bet 45 psi launch would be doable.

And to answer your question, these will fit both a Dana70 Dodge Rearend and Dana80 Dodge Rearend with no modification or changes period.
 
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Definitely adjust the rear, but also make sure you've removed, or zip tied the height based proportional valve on the HR frame rail by the rear axle.
 
Thanks guys. I have a decent direction to go with now. For the record from the Master to the drops is all line I bent and flared. No oem components are left
 
Maybe it is just the mismatch between the size and weight of your left foot compared to your right foot!!! hahahaha
 
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