8.8 swap ?

[Neal'88yj]

I just did an 8.8 swap for my '88YJ and the brake pedal now goes to the floor. I have been told that because of the discs in the rear that the master cyl. needs to be upgraded to handle the added stress. The only trouble is finding one that will match the original mounts and lines. Has anyone had this problem or know what part will work?
Thanks
Neal

[Norm]

It sounds like air in the lines. You don't need to screw with the master cylinder. I pulled the o-ring out of my proportioning valve to give a little more flow to the rear discs. But it worked ok before doing the o-ring trick. If you search you will find some info on how to fix the proportioning valve to give you better rear brakes. But bleed your lines again first.

[Neal'88yj]

Originally posted by Norm
It sounds like air in the lines. You don't need to screw with the master cylinder. I pulled the o-ring out of my proportioning valve to give a little more flow to the rear discs. But it worked ok before doing the o-ring trick. If you search you will find some info on how to fix the proportioning valve to give you better rear brakes. But bleed your lines again first.

I've bled the lines about 3 times and replaced the master cyl. with another stock one and no go. By any chance did your Yj have ABS because I've been told that this would make a differance.

[GOFER]

Originally posted by Neal'88yj


I've bled the lines about 3 times and replaced the master cyl. with another stock one and no go. By any chance did your Yj have ABS because I've been told that this would make a differance.

The calipers will fit on either side make sure the bleeder is on top
Learned this a few years back over one afternoon hehe

[OkLaHoMaYJ]

I have a 95 wrangler with ABS a D44 front and F8.8 rear. I have 4 wheel disc brakes and have a stock master cylinder. Everything on my setup works perfect. Had to bleed the system like 5 times to get everything to work right but the pedal is at stock pedal pressure and only goes down like an 1'' further than it did with the D30 and D35c disc/drum combo.

My waggy is an 85 D44 and my 8.8 is a 98 out of an Exploder. I have stock rubber lines in front as well as stock hard line and rubber line the rear 8.8, if mine works....your's should. I can post pics if need be.

[TornadoTJ]

Originally posted by GOFER


The calipers will fit on either side make sure the bleeder is on top
Learned this a few years back over one afternoon hehe

I was about to say the same thing, I bet that's his problem.

[MossMan]

i found out the same thing when I stalled on a very steep hill and mashed the brakes. pedal felt fine but the rear tires did not lock up, just the front. that was a fun slide back down. Anyway, I removed the o-ring in the prop. valve and it's been good ever since.

[kjp98TJ]

ditto the bleeders on top

[Neal'88yj]

Ok, so if the bleeder valve is on the bottom it'll cause a lack of pressure?
I'll have to check.
as far as the o-ring in the prop. valve, I'm concerned about the safety factor.
( my brke guy refuses to do it)
mine does not have ABS so that is another reason why it's weak.

So no one knows if an ABS unit will fit my mounts and original lines?

[Neal'88yj]

ok, I checked the bleeder valve thing and yes I had them backwards.
But my brake guy took my master cyl. to find a stronger one that will fit.
My question now is has anyone done this swap who doesn't have ABS and is still using the original master cyl.?

[Binderfan2002]

Originally posted by Neal'88yj
ok, I checked the bleeder valve thing and yes I had them backwards.
But my brake guy took my master cyl. to find a stronger one that will fit.
My question now is has anyone done this swap who doesn't have ABS and is still using the original master cyl.?

Thats scary that your break guy dident catch that.

[JeepinDoug]

First off, when you go from rear drum to rear disc you need to pull the residual valve from the master. The drum brakes keep around 9 psi in the wheel cylinders to keep the cylinders from backing off all the way.
The bleeder needs to be on top so you can bleed it properly, air rises the highest point.
If you install a new master you need to bench bleed it, if you don't you'll be scratching you head for a long time.
You need a master with a rear reservoir that has the capacity to fill the calipers. For a CJ an early 70's Corvette master bolts up to the Jeep booster or firewall. These perticular masters also have a large piston, 1-1/8" for more volume per stroke and a shorter pedal throw.

[Neal'88yj]

Originally posted by JeepinDoug
First off, when you go from rear drum to rear disc you need to pull the residual valve from the master. The drum brakes keep around 9 psi in the wheel cylinders to keep the cylinders from backing off all the way.
The bleeder needs to be on top so you can bleed it properly, air rises the highest point.
If you install a new master you need to bench bleed it, if you don't you'll be scratching you head for a long time.
You need a master with a rear reservoir that has the capacity to fill the calipers. For a CJ an early 70's Corvette master bolts up to the Jeep booster or firewall. These perticular masters also have a large piston, 1-1/8" for more volume per stroke and a shorter pedal throw.

Excellent how about for a YJ?

[Neal'88yj]

OK it works you were right bleeder valves upsidedown.

[JeepinDoug]

Originally posted by Neal'88yj


Excellent how about for a YJ?

Being the YJ is an 88' it may use the same booster as a late CJ. Take the booster or old master to VatoZone and start pulling different masters to compare with other masters that were used in 4 wheel disc cars, like the Vette.

[NothernAZxj]

ok, I checked the bleeder valve thing and yes I had them backwards.

Damn dude find your self another Brake guy, he has to be the worst if he cant find that mistake, or did he install them that way himself?!