I recently swapped out my rear Dana 35 for a Ford 8.8 axle. Everything went well, but my only issue is that the rear calipers are simply not getting enough brake fluid. I’ve read across the Internet that the stock master cylinder should be sufficient, but I know for a fact that ideally when pressing on my brakes, they should be tighter. What is my next step? Is there a tweak? Can I take my jeep to a brakes auto shop and they take care of this in a few hours, or do I have to worry about getting myself into a larger project finding a master cylinder etc?
Brake Power after Axle Swap
- Thread starter jaysyro
- Start date
Why are you under the impression you should be getting more out of it? They are supposed to do barely anything at all. My suggestion is leave it alone.
to put it in perspective, the Ford 8.8 uses the same disc brake design that the 2003+ disc brake TJs used. The disc brake TJ used the exact same master cylinder and combination valve as the drum TJs did. The drum TJs used the same drums and combo valve as the YJs did. The YJ used a different master cylinder but only due to the booster design. In short, you have the same combo valve setup as a late TJ and the same rear brakes as late TJ. You do not need to increase the braking back there.
Very very interesting. Considering the front has drum brakes and the back has disc, wouldn’t the proportioning valve at least have to be modified in some way? Why am I now getting a weaker or spongier brake pedal now compared to prior the axle swap?
Front is disc. You have disc/disc, you had disc/drum, TJs had the same parts as you on disc/drum and disc/disc both. So nothing wrong there.
if you have a weak/spongy pedal, are you sure you put the calipers on the right side? The bleeders need to be above the hoses. If they are not then you need to swap the calipers to the other sides. If they are on the correct side then you need to do more bleeding.
Thanks - apparently the mechanic bled them today and still the same. Here’s some photos he sent me after the axle swap. LMK if there’s any red flags you can see …
Calipers appear to be on the proper sides. Maybe he needs to bench bleed the master cylinder? Not sure but I know it’s possible to have a good setup with nothing but stock hydraulic parts to operate the rear disc swap. Mine is that way and is perfect and it makes sense since the TJ came factory that way in later years.
Did mechanic bleed all 4 wheels?
Did mechanic bleed all 4 wheels?
Steve Flame
New Member
Hello!
Master cylinders between disc and drum are different. The 4 wheel disk setups have equal size reservoirs- and no check valves for the rear. The proportioning valve is the same for both setups according to part number. We used to just pull the check valve out of the master cylinder to keep the brakes from dragging. My 94 has a stock master cylinder, I am assuming the check valve was removed because the brakes don't drag- I did not install it. You have to watch your fluid level closely if you use the smaller drum brake reservoir.
However! This should not affect the peddle as in loose or spongy.
I found a video:
Master cylinders between disc and drum are different. The 4 wheel disk setups have equal size reservoirs- and no check valves for the rear. The proportioning valve is the same for both setups according to part number. We used to just pull the check valve out of the master cylinder to keep the brakes from dragging. My 94 has a stock master cylinder, I am assuming the check valve was removed because the brakes don't drag- I did not install it. You have to watch your fluid level closely if you use the smaller drum brake reservoir.
However! This should not affect the peddle as in loose or spongy.
I found a video:
That’s…not really correct. It could depend on application. Jeep is a good example.
The 91-94 4.0 YJ had a single diaphragm booster with a 1” bore cast iron master cylinder. Front disc/rear drum. The 95 introduced a dual diaphragm booster, plastic reservoir MC, still 1” bore.
The 97 TJ introduced a new master cylinder and brake booster but they were the same size and specs as 95 4.0. Same exact drums and front brakes as since 1990.
In 2003, they introduced the rear disc option for Rubicons and any Dana 44 equipped TJ. They kept the exact same combo valve, brake booster, and master cylinder. The truth is that between the stock rear disc and drums, they need the same hydraulic pressure.
You don’t want to remove any of the valving. That is what keeps the rear brakes from being too powerful and locking up. If you lock the rears, you will spin on the road. Not good. The best choice for rear disc is to leave the hydraulics completely alone. Bleed the brakes and call it done.
I’m not sure what the problem is in this post but it isn’t needing to change the hydraulics. I installed the discs and it worked perfectly fine, as it should.
Steve Flame
New Member
Well- now I am up to date again :/ They started phasing out residual check valves in cars manufactured some time in the 70s- there's been none made with them for many years. This is a result of better cup sealing designs in the wheel cylinder. Although apparently you can buy an inline version from Summit with the suggestion it helps with better response at the peddle- might be good for those who still have rear drums?
So master cylinders are the same now other than reservoir size.
Jaysyro- I know that does not apply to your issue, I would still be looking for air in the system- from the information you posted.
So master cylinders are the same now other than reservoir size.
Jaysyro- I know that does not apply to your issue, I would still be looking for air in the system- from the information you posted.