85 clutch MC mount on firewall reinforcement?

The firewall sheet metal where my Clutch MC is mounted on the firewall has fatigued and cracked, to point of being a major safety risk. I need some ideas on fixing it so I am posting this in the Mod section. I am wondering a thick steel plate on the wall inside the cab might work? Under the hood, does not look like a good option.

Is there any other option, thinking outside of the box?

AW4?:gee:

can you just reweld the cracks?
don't listen to the AW4 peanut gallery. where i grew up, only Barbie drove a jeep with an automatic.

old_man said:

AW4?:gee:

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No, it was 2.5 L, 4 banger OEM, now a Nissan Diesel 4 banger, SD-22 engine, 5 speed Nissan manual tranny, but the clutch MC is Jeep OEM, as is the mounting area.

And no, welding does not look like an option to me.

I loaded some photos:

the picture doesnt work. any welding is always an option if it's metal!

Vanimal said:

the picture doesnt work. any welding is always an option if it's metal!

Click to expand...

Picture Doesn't work? Odd they display in my browser, Firefox.

In my experience welds won't hold this sort of problem, the crack will just move.

i dont think it needs to be a 4cyl, i doubt they changed the firewall for a 6cy, or even an automatic for that matter.


it's just a red x.

Bigger photos here:

http://www.naxja.org/forum/showpost.php?p=245655619&postcount=8

mine's a little different, i have a steel brace that bolts to it, as well as the brake booster bolts. the holes might be rotated 90 degrees as well.

Plate on the cab side to spread the load. The bigger the better.

It looks to me like there was a brace from the factory, just not in 84-86. My 84-86 parts catalog doesn't show one, while the 87-90 parts catalog does, but only for factory gassers. For some reason the factory diesels didn't get a brace. The part number for it is 5300 4336.

I think they may have changed the bolt pattern for the clutch master on the firewall between 84-86 and 87-90 though - the pics you show have the bolt holes horizontal while the pics in the 87-90 catalog disagree on whether it's horizontal or vertical* and my 91 is definitely vertical. Looking in the catalog there are like half a dozen part numbers for master cylinders, and I'm not really sure how to get them all straight.

I think you are gonna have to fabricate a brace - it doesn't appear the factory one for later models will fit, if I had to guess. Yet another strange thing about the early models I never knew...

* the pic of the master cylinder shows it as horizontal, but the brace picture only makes sense if it's vertical, and the pic of the repair package for the master cylinder shows it as vertical. I think it's actually vertical and they just forgot to update the main pic of the master cylinder.

Ecomike said:

In my experience welds won't hold this sort of problem, the crack will just move.

Click to expand...

Stop drill the cracks. (to keep them from extending further).

Rivet reinforcement plate over the area with rivets though out the reinforcement plate.

Well, that's the way they fix things with wings anyway, I'm sure it would hold a lousy clutch MC.

I would still like to see images or pictures of later year set ups, 87-90, mainly to see where the other braces terminated to the body - structure.

Mine is definitely horizontal if there was any doubt, so is the single left side brace.

In my case, stop drilling the cracks may be useless, and may cause more problems, as the main crack is an oval that has the exact same shape and size as the clutch MC flange. I later noticed it has reached 50% of flange circumference now. The other two cracks radiate out from the mounting bolt hole, one vertical two horizontal with about a 30 degree spread between them and they terminate at the brake booster reinforcing plate.

I need to find me a midget helper, LOL, but alas I live in Texas where everything is supersized, except the work area under the dash :smsoap:

I like the sound of rivets, but not sure I can get access to all the spots, and I would need plates on both sides from what I am seeing. Looks like I need to focus on adding a brace first to the right side first (passenger side bolt), or even extra braces with a plate (with 1-2 extra bolts and brackets?), and sealant.

Yeah, I think sandwiching the firewall is the way to go. If there is no room for rivets, what about making a nut plate out of the inside plates, and running the bolts in from the engine compartment. Maybe add some epoxy inside the sandwich.

I found this online for 1987-90 (and I think 91-9?):

http://www.factorychryslerparts.com...y_TrimLevel=0&ukey_modelRange=0&searchString=

Hard to tell exactly what is going on with parts 1,2 and 3?

Here is what I seem to have, but it does not show the one brace I have, shown in my photos:

http://www.factorychryslerparts.com/showAssembly.aspx?ukey_product=4286447&ukey_assembly=691689

DO NOT buy from that company. They screwed me over, ignored my email and phone messages, and I ended up having to call my bank to get my money back.

Firewall repair update. The repair has held up so far. Also I switched back to the OEM pressure plate clutch package, that dropped the applied foot pressure force about 50% which should help the firewall repair hold up a lot longer. The HD clutch I had switched to about 12 years ago, no doubt added to the failure damage of the corroded and cracked firewall.