Beretta.net

Well found a 1" bore master cylinder. I will be pulling the Lumina one from my car and installing a 1999 Venture Van master. It's 1" bore and works with ABS. I'm also going to check the bias valves and see if they are different than the ones in there and if so I will re-use those from the Lumina one in the Venture setup. The Venture lists both rear disc or drum for that year and non of the masters were specific to the different setup so I'm not sure how that would work bias wise.

It's one of those 4 port styles? Swapping the bias guts over should be pretty straight forward. Do you have anything to measure spring pressure? You could look and see if the Lumina is more or less rear bias. I'd think the Venture might actually be more rear bias with a heavy mini van. Which would be good since the Neon would be a little lacking in torque compared to n or f-body.

Yes identical to the Lumina... And the Impala one I had is a 1" bore 4 port non abs version if anyone is interested.

No I don't have anything to test the springs but I'll have to compare them and see if they look any different. I'm thinking about getting a fluid pressure gauge so I can see what the actual pressures are after all of this. I compared the 1" Impala one to the stock beretta and the bias valves looked very similar coil and height wise. I'm also very confused on how they get this master to bias properly with the fronts being split between the front and rear ports. It's wrong regarding everything I know on how a master cylinder works.

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What yr impala doesn't have abs that u speak of as im deleting abs in my car while its apart

Can you use a valve spring compressor tool to test brake spring compressor rates?

Edit - found this - ouch on the price:

http://www.jegs.com/i/Proform/778/66775 ... AqT38P8HAQ

These are probably so weak it wouldn't register...

The master I bought was for a 2000 Impala ACDELCO 18M980. With the F-body brakes I think it should pair nicely since the stock bore master on the F-body is 1" as well.

I need to math this out in my head some more because what's confusing to me is the primary and secondary pistons, IF I follow the line assignment correctly, they split the front and rear brakes... Meaning there is a front caliper controlled by each one. typically they would put the primary piston on the fronts and the secondary piston on the rears so if there is a leak in the rear line the primary piston would still operate... The way I think it's configured you would have diagonal brake calipers working if there is a failure. That also confuses me regarding how they actually setup the bias with those two valves... The design of them would have to be opposite of each other if the line assignment is truly what I believe it is.

Eric, you did your lines, is this the right port assignment?

I believe that's the exact pic I worked off of. And yes, diagonals in case of failure to keep car straight-ish.

Master has dual pistons but they are the same diameter - most are. The top output lines get full pressure and the springs reduce pressure to the lowers. I forget how though. There is a rod and an umbrella seal of I remember correctly.

I'll look for the pic.

As pressure overcomes the spring it seals of the back ports. So I believe you get equal pressure until 950, and then only the front rises to 1400.

I have checked my rear rotors recently and they are certainly getting some wear.

woody90gtz wrote:


This pic shows the difference in bias springs for the Beretta vs Lumina master.

Wonder if I can spark off the same debate over here...

The fastest 4T60E-HD in the Beretta world!!!


Went to crap on facebook... Getting called out by Circle track guy saying my crap is slow.

woody90gtz wrote:I believe that's the exact pic I worked off of. And yes, diagonals in case of failure to keep car straight-ish.

Master has dual pistons but they are the same diameter - most are. The top output lines get full pressure and the springs reduce pressure to the lowers. I forget how though. There is a rod and an umbrella seal of I remember correctly.

I'll look for the pic.

Yeah the thing that gets me on the whole setup tho is how can the secondary piston apply the same force as the primary piston when there is a spring between the two of them... The primary is being pushed directly by the booster which then applies pressure to both pistons till the secondary piston reaches a point where it cant move anymore and the spring between the two starts to compress, which in my mind would make the right to left split on the front be different pressures. Once I saw the fronts on the top port and the rears on the bottom the proportioning valves there made perfect sense on how they work. It's the piston setup I can't wrap my little brain around.

The spring & rod assembly is part of the output port of the primary. So it moves the secondary piston hydraulically. There is no compression because it's hydraulically locked. It's just a fail safe in case you lose the primary circuit.

woody90gtz wrote:So it moves the secondary piston hydraulically. There is no compression because it's hydraulically locked. It's just a fail safe in case you lose the primary circuit.

That's the part my brain hadn't processed quite yet.

I can't believe how dirty that transmission is, hopefully you are going to clean that up before you put it back in the car.

It is actually a little dirty, and that shows you that I drive the damn thing. Drivers side is covered in axle grease, the boot strap must not have been tight enough or it was over packed and it spewed everywhere. Also I never painted the HD diff housing yet... that's why it doesn't match.

Things being done to the trans,
New RevMax torque converter... Attempt #2 to see if they got the lockup clutch to work and not slip..
New 4t65e Ratchet sprags for the input clutch and 3rd gear clutch.
Inspect all clutch packs since road course abuse
Freshen Diff and LSD
ZZP aluminum finned trans pan.