95/96 brake booster but keep 91 master cylinder?

[91Pioneer]

OK I think my original brake booster needs replacement, so I'm researching the 95/96 booster swap. My pedal is harder than it should be, feels like it really doesn't have any power assist and once in a while it does have assist. The outside is rusty and it obviously leaked at some point in the past. I have done some diagnosis and figured more than likely the problem is with the booster.

 

Here's my question. Is it possible to swap in just the 95/96 booster but keep my existing 91 master cylinder?

 

I don't want to replace the master cylinder unless I really have to, I plan on picking up a used 95/96 booster since it fits with the least modification. I understand even just swapping the booster may require me to bend my lines a bit to fit better.

[1987Comanche]

  I put a '96 XJ booster and matching XJ/ZJ master cylinder in Georgia my '92 when I got her.  I'm 90%+ sure the older M/C isn't a direct bolt-on or, at least, it didn't appear to be when I removed my leaky one.  Placed side by side there are a fair amount of differences.   

[onlyinajeep726]

It won't work.  The bore and bolt pattern is different.  Also, the diameter of the base that fits inside of the booster is different and would not seal to hold vacuum IIRC. 

[91Pioneer]

Not what I was hoping but OK. I've been keeping my eye out for a 95/96 XJ booster because I want it to bolt in with as little work as possible.

[Incommando]

Master cylindars are relatively cheap anyway even if you have to replace it. I got the booster,master, & valve in one piece and it worked great by just plumbing the lines to the XJ valve and bypassing the rear sensor valve.

[91Pioneer]

My rear sensing valve works great so I'd like to keep it.

[cruiser54]

I prefer 99 to 2004 WJ swap over 95 to 96 XJ having done both. 

[91Pioneer]

Cruiser, would I have to enlarge the hole and flatten the end if I use 99-04 WJ version? And what's the difference?

[cruiser54]

Cruiser, would I have to enlarge the hole and flatten the end if I use 99-04 WJ version? And what's the difference?

Yes, you would. Just as you would with the 95 to 96.

 

WJ versus 95 to 96 XJ booster

 

Actually, the WJ booster is in some ways easier than the 95 to 96 XJ.

 

I've done both.

 

XJ, you don't have to mess with the firewall. No big deal anyway.

But, you have to move the washer reservoir. And, once the original booster comes out, the bracket inside the cab moves and makes it a bear to install the new booster.

 

WJ you have to bend the firewall lip, but don't move the washer bottle.

As an added bonus, the mounting studs of the WJ booster are a bit smaller and it's easier to get in.

Another bonus with the WJ is that it has FLEXIBLE lines from the master cylindere that make putting things together MUCH easier.

[91Pioneer]

I need to research this more. As for the lines I could just use copper-nickel lines, they're easy to work with.

 

My understanding is that 95/96 bolts right into my 91, no hole/grinding necessary.

[cruiser54]

I need to research this more. As for the lines I could just use copper-nickel lines, they're easy to work with.

 

My understanding is that 95/96 bolts right into my 91, no hole/grinding necessary.

Not exactly true.

 The bracket on the cabin side of the firewall tends to move when the stock booster is removed. This necessitates drilling through the firewall and the bracket to get the 95 to 96 booster in there.  

[1987Comanche]

The 96 XJ booster was a direct plug & play in my '92, no drilling, relocation, etc.   I'd think it would be the same in any of the HO trucks.  The only necessary fab work was bending some brake lines. 

[HOrnbrod]

I need to research this more. As for the lines I could just use copper-nickel lines, they're easy to work with.

 

My understanding is that 95/96 bolts right into my 91, no hole/grinding necessary.

 

This is true for your 91. No drilling or whatever. Use the 1/4" spacer if you can then there's no messing with the firewall lip. PnP except for making up new master to distribution block lines. .