M35A3 AT1545 airline question

[Monkeyboyarmy]

Replaced the fuel pump?? Do you mean bypassed the piston pump at the front of the engine? Does it just push through the check valves of the original pump?

The original alternators are pretty good as long as you don't "shock" the system by trying to charge dead batteries or even when you slave another vehicle. Typically the regulator burns out which is replaceable. The 6 little screws attach it to the rear of the alternator. It is not serviceable but occasionally the large resistor is blown out and replaceable. There are US made and Greek made. The regulators are the same except for the outer diameters are slightly different. The 60 amp alternators from the 60's to present are interchangeable if you happen to find a good used one somewhere.
I'm sure everyone would like to see pics of your truck.

 

[glcaines]

I'm not sure why you installed an electric fuel pump and did the bypass. I would recommend bringing the fuel system back to original. Take the alternator off and have it checked out by a shop. Make sure they know ahead of time that it's a 24 VDC alternator.

 

[Sgt Jiggins]

Still working on pics. I will get some up hopefully later today if it's not raining.

The previous owner (a deceased SS member) bypassed the manual pump before I got it. I put the electric one on because it needed "something". I'm open to thoughts on why I should go back... but if it's not going to cause some problem that isn't immediately obvious to me at this point, I kinda like having it. All it does is lead to more fuel return to the tank from what I can see. And it makes starting instantaneous.

I've heard rumor mill grade FUD about the mechanical ones grenading and filling the block with fuel. Is there anything to that?

 

[glcaines]

Still working on pics. I will get some up hopefully later today if it's not raining.

The previous owner (a deceased SS member) bypassed the manual pump before I got it. I put the electric one on because it needed "something". I'm open to thoughts on why I should go back... but if it's not going to cause some problem that isn't immediately obvious to me at this point, I kinda like having it. All it does is lead to more fuel return to the tank from what I can see. And it makes starting instantaneous. I've heard rumor mill grade FUD about the mechanical ones grenading and filling the block with fuel. Is there anything to that?

My M35A3 always starts almost instantaneously. It never turns over more than half a revolution before it fires up. It starts up much faster than my M35A2 multifuel ever did. One thing to be aware of on M35A3s is the check valve in the fitting on top of the fuel tank. Small amounts of trash can, and will, plug it up. It's easy enough to clean, however. I've never heard of one of the original pumps grenading. The CAT engine in my A3 has been extremely reliable. Mine was almost unused when I received it. It still had plastic covering on the drivers seat from the factory. It had only a few thousand miles on it. I've put over 10,000 miles on it since I got it. No drive train issues at all. I did replace the compressor governor with a new one from NAPA. I converted to Dexron III transmission fluid from the motor oil, which made the transmission shift much smoother.

 

[HDN]

Still working on pics. I will get some up hopefully later today if it's not raining.

The previous owner (a deceased SS member) bypassed the manual pump before I got it. I put the electric one on because it needed "something". I'm open to thoughts on why I should go back... but if it's not going to cause some problem that isn't immediately obvious to me at this point, I kinda like having it. All it does is lead to more fuel return to the tank from what I can see. And it makes starting instantaneous.

I've heard rumor mill grade FUD about the mechanical ones grenading and filling the block with fuel. Is there anything to that?

I think I remember that truck being listed on this site for sale!

I haven't heard about exploding fuel pumps, just the cracked alternator bracket really. Like @glcaines my truck starts instantaneously as well with the stock fuel pump unless it's below 45 degrees outside. Had it at a car show last weekend and some attendees were surprised how fast it started!

 

[Sgt Jiggins]

The truck was mentioned on here about a year ago now. Was in NoVA.

IT is what pays the bills for me - I'm certainly no mechanic by trade. But I've picked up a few things along the way, including the idea that the input of others on here is usually worth considering. Hence my position on the fuel pump.

Right now I'm still learning all the smells and sounds and vibrations of the truck. I had an M35A2 years ago and felt pretty confident with it by the end of my time with it. This thing... it's the first automatic transmission I've ever owned for starters. So all the clanking and shift points and occasional slamming into gears is a bit of a learning process.

I do know I have a pretty decent air leak in that 4-way fitting that's on the firewall directly in front of the steering wheel. And the winch lockout switch needs to either be stripped down or replaced. And a new generator/alternator. Other than that, it's pretty much solid.

Stoked to be rolling in it on short trips now. If only the VA DMV were back in any kind of meaningful operational state ... damn you covid.

 

[Sgt Jiggins]

I converted to Dexron III transmission fluid from the motor oil, which made the transmission shift much smoother.

At the recommendation of the guys who rebuilt the tranny, I'm running John Deere hydraulic and transmission fluid. TY6342. Because apparently it makes a difference?? It has all new clutches, but unfortunately not the 4th gear upgrade. Alas, it just wasn't meant to be this go 'round.

 

[glcaines]

Do you have the lock-up torque converter? Some A3s came with them and some didn't. Mine has it.

 

[Sgt Jiggins]

Do you have the lock-up torque converter? Some A3s came with them and some didn't. Mine has it.

That's a good question. How would I know?

 

[tobyS]

They may have been changed out but the entire series used the 1545 which is locking....and really the source of fourth clutch failure. Without locking, fourth would not fail as often. But it would go 3 mph slower max speed. Instead of 50.......47.

 

[HDN]

@Sgt Jiggins mentioned that he had a 1545 installed, which has the locking torque converter. The common 545 does not lock.

Searching the internet, I found that surplus 1545 transmissions were really popular with bus enthusiasts!

 

[tobyS]

@Sgt Jiggins mentioned that he had a 1545 installed, which has the locking torque converter. The common 545 does not lock.

Searching the internet, I found that surplus 1545 transmissions were really popular with bus enthusiasts!

As far as I know, the 1545 was only used with the m35A3. I have a small bus, international 345 gas, that has the 545.

 

[HDN]

As far as I know, the 1545 was only used with the m35A3. I have a small bus, international 345 gas, that has the 545.

I believe that to be true too. Some bus owners wanted the locking torque converter of the 1545, so they bought surplus 1545 transmissions to swap their 545s out with Meanwhile, the TM describes doing the opposite to the M35A3, so it seems like military planners either didn't like the 1545, or figured that the 545 would make more sense to mount being a more-common replacement. That's just speculation though.

 

[glcaines]

That's a good question. How would I know?

If you have the 1545 transmission, you have the lock-up torque converter. If they installed a 545 transmission, you don't have the lock-up feature. When you are driving the truck, you can easily feel the torque converter lock up. From a stop, you can count the four gear changes in the automatic transmission and then you can feel the torque converter lock up. It feels like the transmission has shifted into a 5th gear. The lock-up torque converter increases top speed slightly and increases fuel economy.

 

[tobyS]

The 1545 does give higher speed but It puts more stress on the fourth gear clutch pack .....enough problems the military version never became commercial. Myself, I think a much lighter load of only a single rear axle will help, but I'm wanting lower gears to bring rpm down. I wish I had used the 4l80 clutch and steel piston...but at the time, didn't know how the locking tc caused the added stress.

The committee that made m35a3 did some things right, but not the locking tc on a truck meant to carry up to 10k payload.

 

[Sgt Jiggins]

Mine goes into reverse all day long. 4th... It does, but I find lifting my foot just a little gets it there quicker. Often it's associated with a slamming/banging of (?). I haven't enough experience with them to know if this is normal or a problem. I'm hoping for "normal", but hey...

That last one is a coworker who wanted to drive it.

 

[glcaines]

Nice looking A3! I love mine. It's good you don't have the motor oil in your transmission. The hydraulic fluid in yours will make it shift much better than with the motor oil. I don't worry about weight. I routinely carry up to 3,000 - 4,000 lbs in mine and I sometimes pull a very heavy XM1061E1 trailer.

 

[HDN]

Mine goes into reverse all day long. 4th... It does, but I find lifting my foot just a little gets it there quicker. Often it's associated with a slamming/banging of (?). I haven't enough experience with them to know if this is normal or a problem. I'm hoping for "normal", but hey...

That truck looks nice! Even has a winch I used to let my foot off the gas to force a shift to 4th, but i didn't like the truck slamming itself into 4th. Instead, I put the pedal nearly to the floor and let it shift through the gears at its own pace. I find it shifts pretty smoothly that way. In this manner the truck shifts into 4th between 30 and 35 mph.

The torque converter engaging does feel like extra gear shifts. It was unsettling to me at first because I wasn't used to heavy truck automatic transmissions. I thought it was slipping gears or something, but learned from reading other truck forums that behavior is normal. Now I notice my Chrysler daily drivers even lock the converter it if I watch the tach carefully.

I'm still running 15W-40 in mine and probably won't switch to ATF until it needs a rebuild.

 

[HDN]

I routinely carry up to 3,000 - 4,000 lbs in mine and I sometimes pull a very heavy XM1061E1 trailer.

Carrying in the bed within design limits is one thing, but towing a trailer close to exceeding the truck's towing limit when empty? I'd be worried about breaking the transmission! I'm assuming the AT1545 is the reason why the truck's towing capacity was derated to 6000 lbs. Otherwise I'd love an M1061 to tow!

 

[HDN]

@Sgt Jiggins did you ever figure this one out? I checked under my truck today and found no air lines going into the transmission. The TM doesn't mention any either except for the ones that go past it.

Just a thought: has your air system's air dryer been working properly with ejecting moisture? I'm wondering if one of those air lines goes to it.