M35a2 6x6

I had the same issue with the transfer case in my M813, intermittent engagement, I got solid advice from Ron Harris (KGR).
He instructed me to drain, fill with diesel fuel and drive the truck (un loaded) for a couple miles. He said that when I drain it I'll find scale, crap, and dead bugs in it. Refill and go.
Sure enough when I drained it, scale, crap and three dead spiders came out. Refilled w/ gear oil and it worked as intended.
I'm going to miss that guy.

RollingThunder19 said:

Should I try to drain fluid in TC first and see if getting the TC cleaned out helps first before dropping the whole unit and disassembling the sprag? I would like to not make more work for myself than needed...

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Of course, you can try the flushing method first, if that means less work (and cost) for you.
But in order to pull the front output section you don't need to drop the whole TC. Disconnect the front DS and just unbolt 10 cap screws attaching that part to the main housing.

You mentioned a shift rod and adjustment to it. Where is that adjusted from?

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... From underneath the truck. Read post #1 of this thread...

Scar59 said:

I had the same issue with the transfer case in my M813, intermittent engagement, I got solid advice from Ron Harris (KGR).
He instructed me to drain, fill with diesel fuel and drive the truck (un loaded) for a couple miles. He said that when I drain it I'll find scale, crap, and dead bugs in it. Refill and go.
Sure enough when I drained it, scale, crap and three dead spiders came out. Refilled w/ gear oil and it worked as intended.
I'm going to miss that guy.

Click to expand...

I'll give that a try and see how that turns out with flushing the unit. Also you said drive the truck unloaded, just without anything in the bed?

gringeltaube said:

Of course, you can try the flushing method first, if that means less work (and cost) for you.
But in order to pull the front output section you don't need to drop the whole TC. Disconnect the front DS and just unbolt 10 cap screws attaching that part to the main housing.


... From underneath the truck. Read post #1 of this thread...

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That makes my life easier if I dont need to drop the whole unit to pull the front output section off. Also thanks for the adjustment thread I've been looking for one

RollingThunder19 said:

I'll give that a try and see how that turns out with flushing the unit. Also you said drive the truck unloaded, just without anything in the bed?

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Correct, you want the TC to get warm and have the diesel fuel get good and circulated. No heavy hauling or hill climbing,
just nice level cruise, it may take two flushs. It is worth the time, very easy to drain and fill. Diesel is cheap.

Have you disconnected the linkage and manually tried to push/pull the engagement shaft? It's spring loaded and should return to home position (but not running you may have to help it a little). Don't get in too big of a hurry to take the sprag unit apart if you remove it....lots of small parts and you can see if it is working while together...one side turns one direction and the other turns opposite. Cleaning and inspection of sprag can mostly be done while the sprag is still together (but off the TC).

Scar59 said:

Correct, you want the TC to get warm and have the diesel fuel get good and circulated. No heavy hauling or hill climbing,
just nice level cruise, it may take two flushs. It is worth the time, very easy to drain and fill. Diesel is cheap.

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Okay I'll try that out and see how that goes hopefully that solves the issue. The truck did sit possibly for 7 years so it might just be gummed up.

tobyS said:

Have you disconnected the linkage and manually tried to push/pull the engagement shaft? It's spring loaded and should return to home position (but not running you may have to help it a little). Don't get in too big of a hurry to take the sprag unit apart if you remove it....lots of small parts and you can see if it is working while together...one side turns one direction and the other turns opposite. Cleaning and inspection of sprag can mostly be done while the sprag is still together (but off the TC).

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I havent done anything with the linkage yet only really noticed the issue over the weekend and it's been in the teens so I havent gotten under the truck to see what's all going on with it

RollingThunder19 said:

The truck only has 14k miles on it and I find it hard to believe that anything with the tcase is bad already. I saw some posts say there might be an adjustment for the tcase? Dont know much about that or if that could fix the issue

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porkysplace said:

Your more likely to get the truth out of a politician than the correct hours/miles on a military truck . The government just swaps gauges out they don't fix them.

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Indeed! It's not that your odometer is necessarily a LIAR, but it may (or may not) be the "original" to any specific production or rebuild date consequential to the wear-and-tear or use of your truck.

ONLY if your truck's history is really KNOWN can you trust what the odometer reading shows.

In our case, our M35A2 came out of a complete rebuild at TOOLE in 1991. the County/VFD that we got it from had records showing it was received by them with 5 miles and 30 hours on the meters. Presumably she was only driven around the motorpool and the run time hours accumulated for monthly PM to keep the batteries charged until she was DRMO'd to the VFD. So, I can say with confidence that our Deuce has accurate mileage and hour records.

YOUR RESULTS MAY VARY based on how often the Motor Pool Sergeant sent the newbie out to any random truck to "test" the private's knowledge ability to swap out one instrument panel for another. Or, in the case of a single gauge failure, whole panels are swapped for a fresh one with all working gauges so that the gauge repair/replacement became a bench-job thus getting the truck back in service more quickly. Transportation Officers get upset with Motor Pool Sergeants when too many trucks are REDLINED!!! Records of such swaps were/are seldom maintained.

Ah...dang. I didn't know they'd swap out an entire panel for a single gauge failure. That really throws a wrinkle into things.

I was looking at my panel and observed that the fading of the white marks in my gauges was uniform between the tach, speedo, air and oil pressure but that the bezel and while markings in the volt meter and fuel gauge was cleaner and newer, so I hoped that my mileage and hours was accurate, but maybe or even probably not.

In my opinion I would just replace the whole unit with an air shift case. Even a correctly working sprag case does not work as good as an air shift case.

tie6044 said:

In my opinion I would just replace the whole unit with an air shift case. Even a correctly working sprag case does not work as good as an air shift case.

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Switching over to air shift might be a project in the future. For what I do with the truck now the current setup is working for me. I also have another deuce that has everything I'm looking for on it so I might just spend the money on that

Scar59 said:

Correct, you want the TC to get warm and have the diesel fuel get good and circulated. No heavy hauling or hill climbing,
just nice level cruise, it may take two flushs. It is worth the time, very easy to drain and fill. Diesel is cheap.

Click to expand...

Anyone recommend fluid for the tcase when I go to refill it? I read some posts on trans, tcase to put 40w non detergent in them and 80/90 in axles. If anyone else uses something different I'm open to hear others opinions

RollingThunder19 said:

Anyone recommend fluid for the tcase when I go to refill it? I read some posts on trans, tcase to put 40w non detergent in them and 80/90 in axles. If anyone else uses something different I'm open to hear others opinions

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Unless you plan on driving the vehicle in temperatures -15 degrees and lower the lube order for the transmission, transfer case and differentials call for 80/90.

The transmission calls for 80/90 GL1 oil, the newer stuff last time I looked, is 80/90 GL5. It has to do with the additive packages in the oil. Some of the additives in GL5 are not compatible with the older transmissions. There is more to it, but that is the easy answer. The transfer case and differentials can use 80/90 GL5 without a problem.

For logistics I use 80/90 GL1 in my vehicles. I buy in bulk to save costs and don’t have to worry about “did I put the correct stuff in” kind of thing. I have always figured if it isn’t broke, why fix it. The vehicles have lasted with GL1 for all these years, something must be right.

RollingThunder19 said:

Anyone recommend fluid for the tcase when I go to refill it? I read some posts on trans, tcase to put 40w non detergent in them and 80/90 in axles. If anyone else uses something different I'm open to hear others opinions

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NAPA usually carries GL-1 that's where I get mine.

Scrounger said:

Unless you plan on driving the vehicle in temperatures -15 degrees and lower the lube order for the transmission, transfer case and differentials call for 80/90.

The transmission calls for 80/90 GL1 oil, the newer stuff time last I looked, is 80/90 GL5. It has to do with the additive packages in the oil. Some of the additives in GL5 are not compatible with the older transmissions. There is more to it, but that is the easy answer. The transfer case and differentials can use 80/90 GL5 without a problem.

For logistics I use 80/90 GL1 in my vehicles. I buy in bulk to save costs and don’t have to worry about “did I put the correct stuff in” kind of thing. I have always figured if it isn’t broke, why fix it. The vehicles have lasted with GL1 for all these years, something must be right.

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So everything takes 80/90. I was reading some threads and saw people talk about some things need to be yellow metal safe for transmission? I just want to make sure I put the right stuff in and not end up having to worry

When these vehicles were first made there was 80/90 gear oil. As the oil was improved with additives, they started adding GL numbers. I think the current number is GL5. So, the first oil became GL1. Certain additives in some GL5 formulations harm yellow metals. Now there are GL5 oils out there that comply with MIL Spec number whatever that won’t harm the yellow metals. What they are and who makes them I have never looked. If you buy 80/90 GL1 it works, it is what is called for and it is readily available.

A lot of guys are switching the transmission to 40w non-detergent .
[h=1]Transmission oil clarification[/h]
[h=1]M35A2 gear lube/transmission[/h]

porkysplace said:

A lot of guys are switching the transmission to 40w non-detergent .
Transmission oil clarification


M35A2 gear lube/transmission

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Yeah, few years ago there was a big discussion about oils. I eventually called Spicer who was bought out by "Tremec" . I was able to talk with an oil engineer for about half an hour. According to him most all manual transmissions are going to a 50W synthetic oil. It gives better lubrication and less drag so better fuel economy. So you can use the 80W-90 gear oil or use the newer 40W, 50W gear oils. Just make sure it is a "gear" oil and not an engine oil.