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Topic: TC disc brake rear swapped...but no rear brakes (Read 1078 times) previous topic - next topic

TC disc brake rear swapped...but no rear brakes

I completed the TC disc brake rear swap this evening...everything went great!!  Took two hours from start to finish.  The 3.55's pull much nicer than the 3.08's.  I still need to acquire the appropriate e-brake cables (already read the sticky about that).  But before that...I could not get the rear brakes to work.  I'm getting fluid through the bleeder but no caliper action.

Now I must say that it is possible that the calipers are froze...the donor rear did set for a couple years.  But if that is not the case, is it possible that the proportioning valve is not passing enough fluid to the rear calipers?  The front brakes and MC are stock '88 Sport (for now...and likely for a while).  I have a prop valve from the donor TC that I can swap if that will help with the problem.

Your thoughts?
1988 T-Bird Sport Coupe--5.0 HO, MAF swap, 1-5/8" shorties, BBK/Flowmaster exhaust, Explorer intake, 70mm Edelbrock TB, T5, B&M short throw, Centerforce clutch and PP, disc brake TC rear w/ 3.55's, TC front brakes, '98 Cobra springs, DIY SFC's, other misc .  14.05 @ 98mph with launching too low and shifting too high.

TC disc brake rear swapped...but no rear brakes

Reply #1 –
If you are trying to use a stock disc/drum prop block with rear discs, you aren't going to get them to work much, if at all.

Swap to the proper prop block first.  Then if you still don't have caliper movement, time to deal with seized calipers.
Long live the 4-eyes!  - '83 Tbird Turbo - '85 Marquis LTS - '86 LTD Wagon

TC disc brake rear swapped...but no rear brakes

Reply #2 –
That's exactly your problem.
Usually calipers don't freeze in the open position,they freeze in the closed position.
If you where able to turn them in then they are fine.
Your problem lies in the prop valve and master cyl.
Rear drum brakes require very little fluid to operate and the prop valve is set up to deliver most of it too the front.
You need to get an adjustable prop valve and re proportion the fluid to the rear.
Your master and booster must also be changed to a 1993 cobra which had the exact same combination as you are running now.
Your current master does not have a big enough fluid reserve for the rear and i don't believe that the 93 master will fit the stock 88 booster.

TC disc brake rear swapped...but no rear brakes

Reply #3 –
Quote from: Chuck W;286292
If you are trying to use a stock disc/drum prop block with rear discs, you aren't going to get them to work much, if at all.

Swap to the proper prop block first.  Then if you still don't have caliper movement, time to deal with seized calipers.


I was kinda hoping this was the issue.  Through some searches I did find where several folks said they were running the stock MC w/ four wheel discs with no problems but I never found anything stating that the prop valve was swapped or left stock.  Knowing the front/rear bais with stock dsic/drums I thought this may be the problem.
1988 T-Bird Sport Coupe--5.0 HO, MAF swap, 1-5/8" shorties, BBK/Flowmaster exhaust, Explorer intake, 70mm Edelbrock TB, T5, B&M short throw, Centerforce clutch and PP, disc brake TC rear w/ 3.55's, TC front brakes, '98 Cobra springs, DIY SFC's, other misc .  14.05 @ 98mph with launching too low and shifting too high.
 

TC disc brake rear swapped...but no rear brakes

Reply #4 –
It's not a guarantee that the rear calipers aren't seized, but they wouldn't work regardless if you're trying to use the disc/drum prop block.
Long live the 4-eyes!  - '83 Tbird Turbo - '85 Marquis LTS - '86 LTD Wagon

TC disc brake rear swapped...but no rear brakes

Reply #5 –
Quote from: Chuck W;286333
It's not a guarantee that the rear calipers aren't seized, but they wouldn't work regardless if you're trying to use the disc/drum prop block.


I completely understand...and I'm fully prepared to replaced the rear disc parts with all new.  But I don't want to do that then find out the prop block is still a problem.  I'd prefer to start at the front and work out the kinks as I go back.
1988 T-Bird Sport Coupe--5.0 HO, MAF swap, 1-5/8" shorties, BBK/Flowmaster exhaust, Explorer intake, 70mm Edelbrock TB, T5, B&M short throw, Centerforce clutch and PP, disc brake TC rear w/ 3.55's, TC front brakes, '98 Cobra springs, DIY SFC's, other misc .  14.05 @ 98mph with launching too low and shifting too high.

TC disc brake rear swapped...but no rear brakes

Reply #6 –
Is this a fact that the 93 master cyl will not work with the 88 booster? Does that mean you need to use a 93 cobra prop valve?
1988 Thunderbird Sport. Work in Progress
5.8L swap w/fitech efi, 4R70W swap w/quick 4 controller, 2003 GT rear diff, 5 Lug swap

Bought this car back as an old project car.

:burnout: