Are FJ40/Fj55 brake cylinders interchangeable?

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Eric Ellis

Eric Ellis

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I am opening this thread here as someone might have a definitive insight on the question.


Here is what CDan told me:
CDan showed all of the lines (at the backing plate), backing plates and the like to be of the same part number ergo uniform. The only thing different was the part number for the cylinder itself. He was theorizing that the bore would be the different aspect of the cylinder.


Here is the minimal thread at the tech site: https://forum.ih8mud.com/40-55-seri...rchange-fj55-wheel-cylinders.html#post6529642


Added: Tucker has said they are not interchangeable. I am curious as to why...what the difference would be. Is it indeed bore or is it some other aspect.
 
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shoot, I thought they were the same for each year. this will be good to know.
 
Looks like Cdan is correct on one part of the deal. As per an aftermarket cylinder the 55 has a 15/16 bore vs the 40's 7/8 bore.

I do not know what other differences might exist.

Hard to imagine 1/16 dif. being that great of a deal?
 
I will root around for my old 40 cyl. this next few weeks and pull one off the 55 to examine them more closely.
 
Eric Ellis said:
Looks like Cdan is correct on one part of the deal. As per an aftermarket cylinder the 55 has a 15/16 bore vs the 40's 7/8 bore.

I do not know what other differences might exist.

Hard to imagine 1/16 dif. being that great of a deal?
Click to expand...

wonder if it was for more stopping power for the added weight over a 40?

would that be the same for powered and non boosted cylenders?
 
3_puppies said:
wonder if it was for more stopping power for the added weight over a 40?

would that be the same for powered and non boosted cylenders?
Click to expand...

That would be the assumption- more stopping power.

I will try to find out on the latter.

What years are not boosted?
 
Seems there was a listing for the front brakes with 1 &1/4 bore...to the rear 15/16
 
tucker74 said:
IIRC the shoes are different as well, been a while but remember having a hard time getting all the parts to re-do the brakes on my '73. I got OEM cylinders from CDan and shoes off eBay, but that's been 7-8 years ago now.

Sorry I'm not more help :frown:

Tucker
Click to expand...


Tucker. Thanks for the input. CDan say's everything is the same part # wise. It is just the cylinders that vary w.r.t. part # and it appears to be a bore / stopping power issue.

I am going to try to look more closely in the next couple of weeks.
 
I think this came from Mud...not sure where:

"• Wheel Cylinders are Different
• Wed Jul 9 17:10:14 2003

Front wheel cylinders are single piston, 1 1/8" diameter. Left side (driver's) has right hand threaded adjuster, right side (passenger) has left hand threaded adjuster. All four have bleed fittings, position them closest to tire.

Rear cylinders are double piston, 7/8" diameter. Same story on the adjusters. One bleed fitting per wheel, goes in front of axle, closest to tire.

Front (single piston) has more stopping power, rears have less. In the rear you are splitting the hydraulic force in two and directing it to 8 smaller pistons instead of 4 larger ones."


But this may be for 40's.

Same theory and function but????

Talked to my local Parts folks and they said the front cylinders are the same 9- 71/aka 72 production to 9-75 (just before disc). Earlier #s I have not gotten yet. Both Rt and Both left front have the same numbers respectively (4 cylinders and 2 numbers) with Fj40 and Fj55 having the same part #s on the front but not on the back.

And I still can not imagine the back being and issue with a 1/16th difference. ***on the back that is on one source.
 
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Good write up rsb. Thanks. Here is to hope that the front cylinders are good for rebuilds.
 
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