Ø 1-½" Wheel Cylinders

[Clay James]

I bought some surplus wheel cylinders on ebay to replace the ones on the 109 that didn't hold up to being rebuilt. They are 2009 AM General production, but the bore is 1.5" instead of the 1 3/8". I compared them and they're the same otherwise. Is this a late model update or perhaps they aren't in fact for a deuce? NSN 2530-01-441-4866 Couldn't find anything about what specific vehicle that relates to. Any input appreciated.

 

[doghead]

http://www.parttarget.com/2530-01-441-4866_2530014414866_RCSK17128.html

 

[doghead]

Truck, Cargo, Dropside 2 1/2-TON 6X6 W/E

 

[gringeltaube]

Those are the front axle WCs for the A3-series, TM 9-2320-386-24P, fig.108, item 16.

Its almost 20% more volume (brake fluid), for the same piston travel, compared to the 1-3/8". Should work OK as long as brake shoes are kept well adjusted.


G.

 

[m-35tom]

bonus is you will have better brakes (easier to apply)

 

[peashooter]

That explains why the dual circuit M35A3 Master cylinders have a different volume split between circuits than the 87-89 M35a2 dual circuit trucks did. Never understood why they did that until now.

 

[m-35tom]

Those are the front axle WCs for the A3-series, TM 9-2320-386-24P, fig.108, item 16.

Its almost 20% more volume (brake fluid), for the same piston travel, compared to the 1-3/8". Should work OK as long as brake shoes are kept well adjusted.


G.

do they also fit the rear or are they same as A2??

 

[Clay James]

Thanks for the replies! This will work out great with better braking since they're going in my M109A3 that will be pulling a M105a2 trailer which is going to be a heavy setup.

 

[welldigger]

do they also fit the rear or are they same as A2??

A2's and a3's can use the same wheel cylinders front and back. It may not be optimal, but they fit and work.

 

[gringeltaube]

do they also fit the rear or are they same as A2??

From the books... I say A2 and A3 share the same 1-3/8" WC on the rear axles.

G.

 

[peashooter]

I've got a couple questions on this..

1. Clay, did you ever mount these new larger A3 wheel cylinders on your 109? Did it go okay or did you have issues?

2. Can anyone help me find the part number for the front wheel cylinder "piston pin things" like in the pic below that goes on the M35a3 truck's front axle WC's? I assumed they were the same but I suspect that the A3 trucks use a shorter pin. I havent been able to find it in the A3 tm's yet, only the wheel cylinder itself.

I'm trying to install the a3 cylinders on the front along with new shoes, the larger A3 cylinders appear to not have as deep of "dimples" in the pistons as the stock a2 cylinders do so the shoes dont close enough to get the drum on....hence my thinking that the A3 trucks must use shorter Piston pin things.

 

[welldigger]

The a3 I have worked on had the larger wheel cylinders but I can't remember if the pins were different. I know a2 wc's fit and worked just fine. I never compared the pins.

 

[Jeepsinker]

Peashooter, those are called the "link pins".

 

[welldigger]

Peashooter, if you need to modify something then drill the pockets deeper in the wheel cylinders. The pins don't always come with new wheel cylinders. So if you ever have to replace the wheel cylinders again then the pins can be reused.

 

[peashooter]

Peashooter, if you need to modify something then drill the pockets deeper in the wheel cylinders. The pins don't always come with new wheel cylinders. So if you ever have to replace the wheel cylinders again then the pins can be reused.

yeah I think if any modification, it will probably be to the "link pins" (thanks for the proper term Jeepsinker). Drilling the pocket deeper in the piston would probably work okay but sharp angles such as from a drill bit are where cracks form. I do have access to a nice machine shop so I could make some new pins if needed but I'll probably end up cutting the slot deeper or the other end shorter and just radius it as best as I can on a deburring wheel. Just figured I'd look up the NSN info for the A3 front Link pins to see if they are different and what the official length is for them.

 

[Clay James]

I did get all mine installed and just used the old pins and everything fit fine. I haven't taken it out on the road yet though because of the usual summer major work to it before the next camping trip. Driving it around the ranch it stops very nicely. The pedal is the best it's ever been with the way I adjusted the brakes this time.

 

[peashooter]

Thanks guys,
well I ended up measuring the 2 different pistons with the same link pin. The A3 piston does make the link pin stick out farther so I guess that solves my problem. New shoes and the bigger wheel cylinders are just too much for the standard link pin. I'll just either cut the slot 1/8" deeper on each pin or the rounded end an 1/8" shorter and put a new radius on it.
Left pic is the 1.5" diameter A3 front wheel cylinder, Right pic is the stock 1-3/8" diameter wheel cylinder piston from a2 and rear a3 trucks

 

[gringeltaube]

Interesting. Since the pins are not shown in the A3-parts manual one would assume that they are exactly the same, for all M44-series trucks...?
The ones I have are all from the early times, up to the 70's A2-series, and they all measure 43.5 - 44.0 mm, from inside the slot to the rounded tip.
Someone needs to measure the length of the A3 pins and post up.


G.

 

[welldigger]

First chance I get I'll dig through my buddies bucket of needs to be rebuilt wheel cylinders. I'll see if I can find the a3 link pins or if there is any difference at all between them and standard a2 pins.

 

[peashooter]

Thanks guys,
well I ended up measuring the 2 different pistons with the same link pin. The A3 piston does make the link pin stick out farther so I guess that solves my problem. New shoes and the bigger wheel cylinders are just too much for the standard link pin. I'll just either cut the slot 1/8" deeper on each pin or the rounded end an 1/8" shorter and put a new radius on it.
Left pic is the 1.5" diameter A3 front wheel cylinder, Right pic is the stock 1-3/8" diameter wheel cylinder piston from a2 and rear a3 trucks

Quick follow up. I just cut the slots of the link pins 1/8" deeper and everything worked fine after that and was able to adjust the shoes to spec.