I know the subject has been beaten to death but I need some help making sure I'm on the right track. For starters, My car is a 91 GTA with a drum rear w/ 3.23 gears. I have a line on a 150 9 bolt Posi disc rear. I buy a ton of parts from the owner so I'm sure he will throw in the parking break cable and the brake lines when I get the rear end. My questions are
1.) I read that the pre 89 disc master cylinder is the same as the 90-92 birds so a master cylinder swap is not required.
2.) For a full rebuild that would require: New spider gear set and friction cone set from 9bolt.com. Ratechs complete 9 bolt kit with; Pinion bearings, Pinion shims, Carrier bearings, Carrier shims, Crush sleeve, Pinion seal, and nut. Ring gear bolts, Cover gasket, complete axle bearing set w/ pinion seals. Fresh 3.27 ring and pinion gears, head bearing and tail bearings. should tally up to roughly $438.85 before shipping.

Am I missing anything? I've been trying to get as much info as possible before pulling the trigger on the swap. The rear end will be behind my 383 stealth ram and 700r4 combo. The torque converter is 1800-2100 w/ lockup, and the cam is a Lunati 60121 with 1.6 rockers. Any insight would be appreciated.

 

What gears are in the 9 bolt?

Get a Yukon kit, not Ratech.

You don't need the gears inside the differential unless they are damaged. All you need is the cones, shims and some machine work to rebuild the Borg Warner differential.

 

Why no Ratech?

I'm sorry I thought I put the size. The new rear end has 3.27 gears. I was hoping I could stay close to there given the 700r4 has the tail cone gear for 3.23s I guess if it makes sense to step up the gearing I would be willing to swap over to the 3.70s if it makes more sense. Just not too sure how that wouldr work out with the cam and torque converter.

 

No, the MCs are not the same. You unfortunately have that part exactly backwards.

The old crappy pre-89 discs require a different one. The 89-92 discs will work with a drum MC but the old ones ... have enough trouble as it is.

Frankly, if it was my car, I wouldn't bother.

 

ok so I compared pics of the two master cylinders and I thought I read that the pre 89 master cylinders have one of the break lines coming out of the front of the pv valve. The master cylinder from the donor car and my car seem to be identical. So am I missing something? see pics below for reference.
<b>Donor Car</b>
<a href="http://s63.photobucket.com/user/trae_photo/media/mastercylinder.jpg.html" target="_blank"><img src="http://i63.photobucket.com/albums/h126/trae_photo/mastercylinder.jpg" border="0" alt=" photo mastercylinder.jpg"/></a>

<b> My car</b>
<a href="http://s63.photobucket.com/user/trae_photo/media/mcnina.png.html" target="_blank"><img src="http://i63.photobucket.com/albums/h126/trae_photo/mcnina.png" border="0" alt=" photo mcnina.png"/></a>

 

Don't know about front & back; all I know is, hydraulics. How much fluid they move and what pressure.

The hydraulic requirements of PBRs and drums are similar enough that in several of the PBR years they used the same MC & PV. The old crappy cast-iron discs have sufficiently different hydraulic requirements that they used different ones in ALL of those years.

 

Ratech uses some crappy parts. Yukon kits have higher quality parts.

 

Gotcha, I guess maybe I misread that the pv's would be of a different design or have a different routing. So for a G92 rear end would the stock valve work as far as swapping for the one in my car?

 

$299 from $130 pretty pricey, that big of a difference?

 

Depends on how much you like quality parts verses just good enough. It's worth it to me, but not everybody sees things the way I do. Check and see if there is a USA Standard kit for it.

 

Regarding the master cylinders, I think this may help.