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TRUCK MASTER CYLINDER UPGRADE ADVICE


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I am in process of converting to front disc on my 1939 Plymouth 1/2 ton pickup. I've read where several have had good luck with the Jeep master cylinders. The AC Delco #18M957 (95-2001 Jeep Cherokee) has been successfully used by a few on here for disc / drum systems. This master cylinder has a angled reservoir which on the 95-2001 Jeeps the masters were angled up. When mounted level on our old trucks they can't be filled correctly and look wrong albeit they may work OK. Anyhow, I found another master cylinder that appears to be exactly the same with a level type reservoir. AC Delco #18M802 (97-2006 Jeep Wranglers and some Dodge Dakotas) Anyone have any experience with these? Sure looks like it may work? 

DSCN2415.JPG

Side view AC Delco 18M802.jpg

DSCN2417.JPG

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I know there has been a lot of use with the Jeep MC's,  from doing some research and some input from another forum member, I found a Corvette style that will work, provided the bore stroke is the same, a mounting plate still needs to be fab'd.  77-82 Vette, RockAuto PN# MC39052, this option is more original looking with a quick glance. 

Just my 2 cents. 

Eric

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I agree Eric, the cast iron MC's look better but these more "modern" ones do take up less room. I had adapted a cast iron split master off of an earlier Jeep that I shoe horned in there but the piston diameter was too small and resulted in too much pedal travel. I've heard the 95-01 Cherokee mc's work well?

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5 hours ago, PT81PlymouthPickup said:

I agree Eric, the cast iron MC's look better but these more "modern" ones do take up less room. I had adapted a cast iron split master off of an earlier Jeep that I shoe horned in there but the piston diameter was too small and resulted in too much pedal travel. I've heard the 95-01 Cherokee mc's work well?

From what I've heard with from other's on the forum, the Cherokee MC's work well. I wasn't aware of the big difference in sizes. 

 

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My Jeep reservoir is straight up and down, not angled like pictured above. If anyone plans to use any “corvette” swaps, do a pile of research and don’t cheap out...90% of those kits they sell or aftermarket masters are junk, within the last 6 mo my buddies shop has put 2 brand new ones on and neither was any good.

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15 hours ago, NiftyFifty said:

My Jeep reservoir is straight up and down, not angled like pictured above. If anyone plans to use any “corvette” swaps, do a pile of research and don’t cheap out...90% of those kits they sell or aftermarket masters are junk, within the last 6 mo my buddies shop has put 2 brand new ones on and neither was any good.

Might you remember the part # of the m.c. you used?

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1 minute ago, bkahler said:

The Speedway motors mc is 8" long.  The original mc on my truck is 6-1/2" from the mounting point to the end of the pipe plug. 

 

Unfortunately I don't have the steering column installed yet to know if there would be clearance issues.

Keep in mind the 1/4" to fab a proper mount for the change. 

 

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3 hours ago, rockingjd said:

The mounting pattern in your picture looks to be the same as on my 49 1/2 ton. I used a Toyota Celica master cylinder. 86 to 89 no ABS. Opened up the meteric holes to fit standard bolts and it fits into the original bolt pattern. No adapter plate required. 

Did you experience and increase in pedal travel after converting to the smaller bore toyota master cylinder?

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I used a M/C from a 2002 Jeep Grand Cherokee in my 52. Works very well. There is enough room in your truck for one of these even with an adapter plate. One of the reasons I chose this M/C is that it is a direct match up to the Grand Cherokee rear axle I fitted. Having 12" discs in the rear is really really nice. With the rustyhope kit on the front and these discs on the rear my truck easily handles the silly drivers I have to share the road with here. I just don't have to worry about braking as the truck stops much like a modern vehicle.

Also the 3.55 ratio axle works well in higher speed commuting that we have here in SoCal.

This installation has been pretty much fit and forget.

Hth, Jeff

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On 1/5/2020 at 11:29 AM, PT81PlymouthPickup said:

I am in process of converting to front disc on my 1939 Plymouth 1/2 ton pickup. I've read where several have had good luck with the Jeep master cylinders. The AC Delco #18M957 (95-2001 Jeep Cherokee) has been successfully used by a few on here for disc / drum systems. This master cylinder has a angled reservoir which on the 95-2001 Jeeps the masters were angled up. When mounted level on our old trucks they can't be filled correctly and look wrong albeit they may work OK. Anyhow, I found another master cylinder that appears to be exactly the same with a level type reservoir. AC Delco #18M802 (97-2006 Jeep Wranglers and some Dodge Dakotas) Anyone have any experience with these? Sure looks like it may work? 

DSCN2415.JPG

Side view AC Delco 18M802.jpg

DSCN2417.JPG

 

Did you mount this master cylinder?  If so how well is it working?

 

I'm going to be buying a new MC for my truck now that I'm installing a Grand Cherokee rear axle and any details you can provide would be great!

 

Thanks,

 

Brad

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I just ordered this 1994 Jeep Cherokee master cylinder in the hopes that it will do the job.  I have not been able to find any listing that stated the mounted length so that still might be a problem.  I should know tomorrow night whether it will fit or not.

 

I do know it has the same piston stroke as my original MC and has a 1" bore.  It also uses standard inverted flare fittings.  

 

Stay tuned......

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Ok, I received that MC yesterday and can safely say it won't work in my B3B.  It measures 8-1/8" or so from mounting surface to the opposite end.  Way to long.  I bolted my steering gearbox to the frame and took a measurement and the absolute longest MC that will fit is 6-1/2".   So today I went to the salvage yard and bought a 2002 MC from a Grand Cherokee with 4 wheel disc brakes and it measures just under 6".  I'll post pictures of the adapter plate that I'm going to make once it's done.

 

Brad

 

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Took the first couple of steps in making the MC adapter plate.   As near as I can determine the three mounting holes for the original MC form an equilateral triangle with sides of 2-5/8".  The bore of the MC seems to be placed in the center of the triangle.  The Cherokee MC has all three holes on the same line so it was just a matter of lining all the dimensions up and then making a paper cut out to test my theory.   The mounting holes for the Cherokee MC appear to be slightly more than 3-1/2" apart so I used 3-17/32" as the mounting bolt pattern.  The OD of the Cherokee MC is smaller than the original MC and measures a little under 1-3/4" and will be centered in the same place as the original MC.  

 

20200119_141305x.thumb.jpg.9b1f6e0a53e29c141db30d8061189c17.jpg

 

Using my milling machine with a digital readout I laid out the hole pattern with accuracy around of around .002" or so.  I made the template out of 1/4" aluminum plate and will use alignment punches to transfer the holes in the template to the actual plate I'm going to be using.  It will be much quicker and easier to do the actually drilling on a drill press rather than the milling machine which is why opted to make the template.  Plus it will be easier to make extras :)

 

Current plans are to countersink the two holes that mount the Cherokee MC and then use lock nuts to hold it to the adapter plate.  I hope to use regular hex head bolts to fasten the adapter to the truck but will use socket head cap screws if there are clearance issues between the Cherokee MC and the three mounting bolts.

 

I ordered some 3/8" thick aluminum plate to make the actual adapter plate.  Ignore the size of my aluminum template, it's just a piece of scrap 1/4" aluminum plate I had laying around.   

 

It will probably be a week or so before the 3/8" plate order arrives.  I'll post more when I work on it again.

 

Brad

 

 

 

 

 

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