M35A3 Owners unite

[glcaines]

These regulators have a very high failure rate. Either bypass it or replace it. They are an easy to find item and quite easy to replace. This would also be a good time to give one or two squirts of air tool oil into the input side of the actuator.

 

[goodguyzy]

this may sound stupid but pull a head light and see if you have voltage, the alternators go bad a lot and my have blown a bunch of light and never was fixed. A place to start at least, then work your way back.

 

[rossbart]

Good news and BAD? news:

GOOD NEWS: I ran to the NAPA store and bought a simple female/female union and just bypassed the regulator. Walla, very nice steering and no more air problems. While I was down there i also (maybe?) discovered why the front tires didn't want to air up the same as the rear axles using the CTIS on recovery at Ft. Hood. There are a couple of brackets bolted to the top of the axle holding the brake lines before the rubber section goes to the wheels. The bolts were out of both of these. Am I right in guessing the axle housing is pressurized by air and was leaking out of these two open bolt holes?

BAD NEWS: I appeared to have the common leak on the transmission filter and was planning to just replace the filter (assuming the leak was coming from that gasket since the oil was leaking off of the filter canister below it). However, today (while test driving my new power steering around the farm) I noticed that the small leak had gotten much bigger. Upon closer inspection, the fluid is coming from the lower radiator hose (which is right over the tranny filter housing) but UNFORTUNTELY it didn't look like coolant but rather thin oil.

So, I cracked the petcock on the radiator hoping to find clean, green coolant but - sure enough - it was the same thin oily dark stuff. After letting the truck cool (and coolant settle) I would get just an ounce or so of oil and then it would turn to nice green coolant. I'm assuming that the two seperate pretty quickly by weight apparently with the oil being heavier. But, as soon as you start it and the coolant pressures up, it is definintely not green - just looks like thin, fairly clean oil - dripping out of the radiator via a cracked lower radiator hose.

My (mostly uninformed) guess is that I have a leaking (failed) internal transmission cooler in the radiator. If I'm looking at the TM's correctly, the transmission fluid (which is still 15w40 from uncle sam) goes through the external filter then through the external transmission cooler then through the internal cooler (inside the radiator) and then back to the transmission. Or, maybe it's the other direction but that's the circuit.

I've only driven the truck maybe 20 miles and no highway miles and it still seems to be shifting just fine (thank goodness). The engine oil level appears to be unchanged and the engine oil still looks and smells very new & clean and uncontaminated. And, the engine runs absolutely perfectly - smooth as a kitten - and no smoking or anything whatsoever.

The transmission fluid (on the other hand) is just barely on the dipstick. I'll admit I didn't check it when we recovered it because it seemed to shift just fine. As to what the transmission fluid looks like, I can't tell from the stick.

Anyone here have a good grasp of the transmission coolant systems on these trucks as well as the radiator? Would I assume that the pressure of the transmission fluid pump is greater than the coolant pressure and, therefore, the transmission fluid (15w40) is leaking into the antifreeze instead of the other way around (hence the low tranny fluid level)? The transmission is still shifting just fine too - I had no symptoms of this at all - YET. Of course, the extra coolant fluid is probably just overflowing out and I haven't noticed it.

So, PART ONE: Do you experts think I'm diagnosing my problem correctly and
PART TWO: What to do about it?

If that IS the problem I'm wondering if I might be able to just bypass the internal cooler and re-route the coolant lines direct to the external cooler? I will be switching over to Transynd Dex III when I refill the tranny and I understand that results in cooler transmission fluid. Also, I'll probably never run this on the highway much or do any trailer towing as this is really just a farm toy. Basically my questions is - does anyone know if the internal transmission cooler is absolutely necessary or just extra insurance? Of course, having the transmission fluid guage will really help here as I guess I can try it and find out what that does to the temps.

Thanks for any help, suggestions and/or advice.

Ross

 

[BadMastard]

I'm sorry to hear that your truck is not a happy camper.

My quick two cents? I don't think the flow through the radiator is for cooling, I think it's for heating the transmission fluid to operating temps, but that's just my guess. I would love to find out if there is a bypass for it when hot, which would confirm my suspicions. If you go with dex III or transynd I suspect your need for the radiator would diminish, except for exceptionally cold weather. What do you think?

 

[AceHigh]

The axle housing is not pressurized, otherwise the seals would pop.

I take the transmission filter off and let it run into a pail so I am not sure of the pressure, but the transmission does put out a lot of fluid in a short time.

 

[glcaines]

The axle housing is not pressurized, otherwise the seals would pop.

Ditto on the axle housings not being pressurized - or at least they are not supposed to be. From the OP, I couldn't tell if air is coming from the bolt holes or not. If air is coming from the bolt holes or from the axle vent, one or more of the CTIS hub seals is shot.

On the oil in the coolant, oil is lighter than water so any oil in the coolant would not be settling on the bottom, it would rise to the top.

 

[Hoefler]

Hello, have two M35A3-one with long wheelbase

 

[BIGDDV]

we bought two M35a3's thru our church water for life ministry. we are making one a support truck with a 1000 gal water tank and pipe racks for the pcv for casing the wells. the other one we are going to part out because of titling issues. we have removed the ctis system from truck 1 and will be posting all the parts in the classified soon.

 

[1 Patriot-of-many]

Ditto on the axle housings not being pressurized - or at least they are not supposed to be. From the OP, I couldn't tell if air is coming from the bolt holes or not. If air is coming from the bolt holes or from the axle vent, one or more of the CTIS hub seals is shot.

On the oil in the coolant, oil is lighter than water so any oil in the coolant would not be settling on the bottom, it would rise to the top.

Are you guys sure? I'm screwed then. Everytime I use CTIS I get venting from at least my rear axle(two vents on top of axle) while the middle tire I have a leak on is filling. I thought that would be how ctis keeps other tires from overinflating for some stupid reason. Crap. Guess my time and bank account are about to be further depleted.

 

[BIGDDV]

the hubs are pressurized but not the axle itself. there is an o-ring behind the inner bearing. sounds like yours are leaking
hard to see the oring, goes on back of spindle against air-pack. wish I had taken pictures last week

 

[1 Patriot-of-many]

I just noticed, you're supposed to drive 3-5 miles(or maybe kilometers) before turning CTIS on according to the operators manual for better sealing, maybe that's why I'm getting venting? I've been doing it cold, cause of a slow leaking wheel oring( about a day or two tire goes flat)

I'll have to cold, inflate the tire by gladhand, drive a few miles, deflate the tire then turn the CTIS on and see if I still get the venting.

 

[jaymcb]

ugh. another CTIS deficiency. Why the heck wouldn't you want it to set your inflation before you drove it?

I'm supposed to be getting a new head shipped to me, so I can see if my system even works.

 

[1 Patriot-of-many]

Good news and BAD? news:

GOOD NEWS: I ran to the NAPA store and bought a simple female/female union and just bypassed the regulator. Walla, very nice steering and no more air problems. While I was down there i also (maybe?) discovered why the front tires didn't want to air up the same as the rear axles using the CTIS on recovery at Ft. Hood. There are a couple of brackets bolted to the top of the axle holding the brake lines before the rubber section goes to the wheels. The bolts were out of both of these. Am I right in guessing the axle housing is pressurized by air and was leaking out of these two open bolt holes?

BAD NEWS: I appeared to have the common leak on the transmission filter and was planning to just replace the filter (assuming the leak was coming from that gasket since the oil was leaking off of the filter canister below it). However, today (while test driving my new power steering around the farm) I noticed that the small leak had gotten much bigger. Upon closer inspection, the fluid is coming from the lower radiator hose (which is right over the tranny filter housing) but UNFORTUNTELY it didn't look like coolant but rather thin oil.

So, I cracked the petcock on the radiator hoping to find clean, green coolant but - sure enough - it was the same thin oily dark stuff. After letting the truck cool (and coolant settle) I would get just an ounce or so of oil and then it would turn to nice green coolant. I'm assuming that the two seperate pretty quickly by weight apparently with the oil being heavier. But, as soon as you start it and the coolant pressures up, it is definintely not green - just looks like thin, fairly clean oil - dripping out of the radiator via a cracked lower radiator hose.

My (mostly uninformed) guess is that I have a leaking (failed) internal transmission cooler in the radiator. If I'm looking at the TM's correctly, the transmission fluid (which is still 15w40 from uncle sam) goes through the external filter then through the external transmission cooler then through the internal cooler (inside the radiator) and then back to the transmission. Or, maybe it's the other direction but that's the circuit.

I've only driven the truck maybe 20 miles and no highway miles and it still seems to be shifting just fine (thank goodness). The engine oil level appears to be unchanged and the engine oil still looks and smells very new & clean and uncontaminated. And, the engine runs absolutely perfectly - smooth as a kitten - and no smoking or anything whatsoever.

The transmission fluid (on the other hand) is just barely on the dipstick. I'll admit I didn't check it when we recovered it because it seemed to shift just fine. As to what the transmission fluid looks like, I can't tell from the stick.

Anyone here have a good grasp of the transmission coolant systems on these trucks as well as the radiator? Would I assume that the pressure of the transmission fluid pump is greater than the coolant pressure and, therefore, the transmission fluid (15w40) is leaking into the antifreeze instead of the other way around (hence the low tranny fluid level)? The transmission is still shifting just fine too - I had no symptoms of this at all - YET. Of course, the extra coolant fluid is probably just overflowing out and I haven't noticed it.

So, PART ONE: Do you experts think I'm diagnosing my problem correctly and
PART TWO: What to do about it?

If that IS the problem I'm wondering if I might be able to just bypass the internal cooler and re-route the coolant lines direct to the external cooler? I will be switching over to Transynd Dex III when I refill the tranny and I understand that results in cooler transmission fluid. Also, I'll probably never run this on the highway much or do any trailer towing as this is really just a farm toy. Basically my questions is - does anyone know if the internal transmission cooler is absolutely necessary or just extra insurance? Of course, having the transmission fluid guage will really help here as I guess I can try it and find out what that does to the temps.

Thanks for any help, suggestions and/or advice.

Ross

Hey Ross, I tried to copy and paste from the PDF. Don't sweat the reading from the stick, the first time. Download and read
TM 9-2320-386-10 read page 2-34 and 2-34.1
I checked it cold not running myself and said WTF? When I read the directions It was right on the money. Also somewhere I read pull the dipstick out slowly or you'll get an inaccurate reading.

 

[1 Patriot-of-many]

ugh. another CTIS deficiency. Why the heck wouldn't you want it to set your inflation before you drove it?

I'm supposed to be getting a new head shipped to me, so I can see if my system even works.

Yeah that's no *&(^ !

I hope it does Jay, cause the system is great. Works fine on my truck and I LIKE IT. Deflates, inflates as the head tells it too.

BTW Ross, sorry for hijacking your thread, it really took a turn from tranny to CTIS.

 

[BadMastard]

Hey 1 Patriot of many,

On your inner seal, it's pretty easy to replace. It's just a o ring, and you can get them from mcmaster carr. I'll see if I can find the part number, but I think I got them from a search here.

But I don't think that's what's pressuring your axles. That seal, if bad would just allow what's in the hub to leak out the back of the hub. If what you are saying is that you have leaks out the caps on top of the axles (vents) then most likely it's backfeeding up the axles from the outer seals on the hub. Could be the oring on the outer hub or the xring or the outer hub axle seal, but all are replaceable. Could also just be a loose axle nut, so it's not sealing.

Mostly because the only place for air to go back up the axle would be on the axle shafts. Same for the gear oil to leak out. Unless the inner CTIS fitting on the axle is bad, but I'm not even going there. That would suck.

That's just from taking apart my axles. After seeing all the parts, I now know why it's so problematic, because you have so many seals that can fail, or just loosen. It looks like once it's sealed up though, it should be pretty happy.

good luck!

 

[1 Patriot-of-many]

Hey 1 Patriot of many,

On your inner seal, it's pretty easy to replace. It's just a o ring, and you can get them from mcmaster carr. I'll see if I can find the part number, but I think I got them from a search here.

But I don't think that's what's pressuring your axles. That seal, if bad would just allow what's in the hub to leak out the back of the hub. If what you are saying is that you have leaks out the caps on top of the axles (vents) then most likely it's backfeeding up the axles from the outer seals on the hub. Could be the oring on the outer hub or the xring or the outer hub axle seal, but all are replaceable. Could also just be a loose axle nut, so it's not sealing.

Mostly because the only place for air to go back up the axle would be on the axle shafts. Same for the gear oil to leak out. Unless the inner CTIS fitting on the axle is bad, but I'm not even going there. That would suck.

That's just from taking apart my axles. After seeing all the parts, I now know why it's so problematic, because you have so many seals that can fail, or just loosen. It looks like once it's sealed up though, it should be pretty happy.

good luck!

Exactly. It's not leaking out the back of the hub, just venting at the top of the axle and I'm not sure it does it when hot(driven), just when I am pumping up the tire without driving, though that is NOT confirmed as yet.

That's what I'm thinking, outer seal or axle nut not tight, though the operators manual tells you specifically to drive 3-5 miles before turning on CTIS..
TM 9-2320-386-10
2-19. OPERATION OF CENTRAL TIRE INFLATION SYSTEM (CTIS)
(2) Drive the vehicle 3-5 miles (5-8 km) to allow seals to seat properly, especially in cold environments.

The gear oil leaking was the gasket where the Axle is attached(wasn't leaking until I removed the two bolts to take off the rock shield for wheel removal.) Once I put some rtv sealant on the 2 bolts the leakage stopped.

 

[camp9]

This came from the other A3 site for the o-rings, I cut and pasted this from a post from
motomacguyver , I don't know if he's here on SS or not


I ordered O rings from a mil-surp vendor. Turns out I could have saved A LOT of money by just getting O rings from MC master Carr. Mc master Carr will sell to anyone, by credit card, but you have to do a certain amount of business to get a catalog. But the online catalog is pretty good.

You will need 1 each of a dash 143 (Mc master carr # 9452k149) and a dash 151 (# 9452k15 O ring in your choice of materials. Buna-N is about 8$/50 and silicone is about 8$/10.

You will also need 2 ea. of dash 238 (# 90025k396) of double seal O rings, (look like an x in cross section) These are only available in stock in Buna-N.

If you order 1 each of these from Mcmaster, you will have enough to do the whole truck and have leftovers.

The rest is cut and paste from the website.

With four sealing surfaces, you'll get twice the sealing protection as standard O-rings. Also known as Quattro Seals and X-rings, double-seal O-rings are symmetrically designed for sealing on the ID, OD, top, and bottom. This reduces the amount of force needed to create a positive seal, increasing seal life and reducing maintenance. All meet ASTM D2000/SAE J200.


Viton® fluoroelastomer works well in higher temperatures, with a range of -15° to +400° F. Durometer hardness is A75. Color is

Buna-N is used in oil applications. Temperature range is -35° to +250° F. Durometer hardness is A70. Meets ASTM D2000/SAE J200. Color is black

 

[glcaines]

Motomacguyver is dead on with his post. I bought all of my o-rings and X-rings from McMaster Carr and have a lifetime supply. These are very easy to replace once the hub is removed and the TM has very good directions. What I am doing every time I pull a wheel from my A3 is to pull the hub and replace the o-rings, X-rings and outer seal and grease the bearings. It doesn't take that long, the biggest hassle being the removal of the wheel and CTIS wheel valve. Once you do one, it is a piece of cake. As a side note, don't separate the hub and drum like the TM says. This is unnecessary if you are careful and keep everything clean.

 

[RealCavDog]

Motomacguyver is dead on with his post. I bought all of my o-rings and X-rings from McMaster Carr and have a lifetime supply. These are very easy to replace once the hub is removed and the TM has very good directions. What I am doing every time I pull a wheel from my A3 is to pull the hub and replace the o-rings, X-rings and outer seal and grease the bearings. It doesn't take that long, the biggest hassle being the removal of the wheel and CTIS wheel valve. Once you do one, it is a piece of cake. As a side note, don't separate the hub and drum like the TM says. This is unnecessary if you are careful and keep everything clean.

All was going good until I pulled the double seal o-rings, quad rings, x-rings, all the same name for the same part, from the seal retainers and saw that they were much smaller than the 90025K396 or dash 238 seals that I ordered from McMaster Carr !

Could somebody check the number on thier order form or reciept and verify that number ! All ready to go back together , but the I.D. on my old rings are about 3.075 and the new ones are about 3.50 !

Other than this hiccup, the whole pcocess is very straight forward and NO NEED to seperate the hub and drum ! Had to work 21 days straight, and thought I had all the parts ready to go . . . . oh well ! The old rings look great under magnification, and I think the recurring issue of under torqued axle nuts may have been the issue, but a bit hesitant to cut corners !

 

[motomacguyver]

Motomacguyver present.