• When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.

Plastic Firewall Gasket and Dr Diff 15/16 Master Cylinder

JR_Charger

Well-Known Member
Local time
3:58 PM
Joined
Sep 30, 2020
Messages
7,578
Reaction score
14,294
Location
____
The gasket will not sit flush against the Dr Diff mounting adapter. The gasket is for a drum car. What do I need to do here?
master_cylinder_plastic_gasket.JPG
 
Looks like you need to enlarge the hole in the firewall and gasket. Edit:In the picture the studs go threw the firewall into the interior? On the threaded side of the plate that raised area does that go in the firewall.
 
Last edited:
I sure hope I don't have to change the hole in the firewall. I know there are people here who have the DoctorDiff 15/16 master cylinder. I haven't seen any install issues in their threads. Strange.

Anyway, the rubber boot over the brake pedal push rod fastens on to the plastic gasket, so the gasket should be kept, but there's nothing wrong with putting another gasket in there. I'd need to put some spacers on the studs so the MC doesn't rock. I'm very slight concerned about pedal travel issues, but it probably won't be a problem.
 
I sure hope I don't have to change the hole in the firewall. I know there are people here who have the DoctorDiff 15/16 master cylinder. I haven't seen any install issues in their threads. Strange.
The hole in the firewall should already be big enough to accommodate a p/b unit so I don't think that will be an issue. Also, all those Mopar/Strange masters are the same casting regardless of bore size. So if a 15/16 fits, so will that one. The rubber boot should go on the master BEFORE the black adapter - there should be a relief in either the adapter or the master to sandwich the rubber boot. Toss that plastic thing in the trash - the rust stains indicate it leaks anyway !!
 
Question. I just finished putting in new brake lines, shoes, and master cylinder. I’m now working on the brake pedal and maybe I’m just getting old, but the pedal seems to be sitting high and it’s uncomfortable to reach. I measured the brake pad height from the padded floor and it’s about 7 inches, which seems to be in line with some of the posts about it.
It’s been a dozen years or so since I put on remanufactured MC and as I recall, there was a plastic gasket that looked liked the one pictured on this thread that I removed. The gasket was brittle and it broke when handled. The new MC came with a foam gasket which has pretty much been used up. This new MC didn’t come with a gasket. It’s hard to tell from the photo, but the gasket shown could be 1/8” ?.
I have a little play in the pushrod and I can lift the pedal about an inch, which translates to movement at the pushrod of maybe 3/16”- 1/4”. I’m trying to figure out if a 1/8” gasket on MC would get me any height reduction on the brake pedal.
 
Question. I just finished putting in new brake lines, shoes, and master cylinder. I’m now working on the brake pedal and maybe I’m just getting old, but the pedal seems to be sitting high and it’s uncomfortable to reach. I measured the brake pad height from the padded floor and it’s about 7 inches, which seems to be in line with some of the posts about it.
It’s been a dozen years or so since I put on remanufactured MC and as I recall, there was a plastic gasket that looked liked the one pictured on this thread that I removed. The gasket was brittle and it broke when handled. The new MC came with a foam gasket which has pretty much been used up. This new MC didn’t come with a gasket. It’s hard to tell from the photo, but the gasket shown could be 1/8” ?.
I have a little play in the pushrod and I can lift the pedal about an inch, which translates to movement at the pushrod of maybe 3/16”- 1/4”. I’m trying to figure out if a 1/8” gasket on MC would get me any height reduction on the brake pedal.
Pedal height is determined by the "stop" on the pedal frame. There is a rubber "damper" there and if that is missing it will result in the pedal coming up higher (and potentially pulling the pushrod out of the m/c).
 
I just looked again and all there is, is a brake light switch that is about halfway repressed with the pushrod resting on it. I can push the switch in more without the pushrod moving. The switch is attached to a bracket that appears to be adjustable. No places for any rubber stop to attach to that I can see.

To OP, if you decide to pitch that what appears to be plastic or hard neoprene material gasket, you can pitch it my way.
 
I just looked again and all there is, is a brake light switch that is about halfway repressed with the pushrod resting on it. I can push the switch in more without the pushrod moving. The switch is attached to a bracket that appears to be adjustable. No places for any rubber stop to attach to that I can see.

To OP, if you decide to pitch that what appears to be plastic or hard neoprene material gasket, you can pitch it my way.

I'm sure I've seen new ones available. It's not at Detroit Muscle Technology ATM. Maybe someone else will know who has them?
 
Auto Transport Service
Back
Top