M813A1 transmission.

[Milton1988]

Hello everyone. Thanks for letting me in. I have a 1970 m813A1, and it seems as if I lost fifth gear. I adjusted the clutch a few days ago and now it won’t stay in 5th. Every other gear shifts and grabs just fine, but when shifting to 5th, it goes in, but as soon as I start to engage the clutch it kicks it right out of 5th. I tried double clutching, power shifting, shifting into 5th while the truck is sitting still, hi range, low range, and nothing.

My question is, before I Jimmy rig a chain hoist in the cab to lower the transmission out of it, is there anything I should check first? I don’t know much about the truck because I just bought it. I did notice once while messing around in low range that there was an air release “psst” sound while shifting between gears but that only happened a few times. Is that something that should be happening every time I shift? Should I change the fluid in the trans to see if it’ll help? Is there some sort of electronic device I should check that allows it to go into 5th? Also, other than that cross member being in the way, I think I can rig up some stuff to pull the tranny out myself. If so, how delicate is the process of just rebuilding it on my own? Is there a possibility that I can take the tranny apart and rebuild it while it’s still mounted on the truck? Any help and advice is greatly appreciated. I priced out a new rebuilt 6453 for 1900 + shipping and it’s something I can do, but before I go and spend 900$ on the freight shipping for a new one, I figured I’d ask here. Thank you!

 

[swbradley1]

Did you look in the manuals to see if there is an adjustment (other than clutch)? No electronics. They use air to do things.

Mine that I sold was a great truck.

 

[Milton1988]

Did you look in the manuals to see if there is an adjustment (other than clutch)? No electronics. They use air to do things.

Mine that I sold was a great truck.

I did look in the manuals, but only clutch adjustment is what I could find. What do they use air to do and where do I look to see if that’s the issue? Is it possible that 5th uses air to engage?

 

[NDT]

Air is used to shift the transfer case, has nothing to do with 5th gear.
Usually jumping out of gear is due to the bearings on the sector shaft being shot, this cannot be fixed in frame. Suggest you pull the cover and look for obvious problems with the shift forks before pulling the transmission.

 

[swbradley1]

It uses air for reverse and not 5th gear. When you put it into reverse you will hear and maybe feel it.

I'm not a transmission guy and there isn't any linkage to adjust but you can take off the top cover and look at it.

 

[swbradley1]

Yeah, what NDT said, I was typing and he posted.

https://www.steelsoldiers.com/attachments/tm9-2320-260-20p-5ton-pdf.482711/

figures 133-139

 

[Milton1988]

Air is used to shift the transfer case, has nothing to do with 5th gear.
Usually jumping out of gear is due to the bearings on the sector shaft being shot, this cannot be fixed in frame. Suggest you pull the cover and look for obvious problems with the shift forks before pulling the transmission.

As in remove the dog house cover and shifter to see if there’s an issue there?

 

[NDT]

As in remove the dog house cover and shifter to see if there’s an issue there?

That would be my suggestion.

 

[Milton1988]

It uses air for reverse and not 5th gear. When you put it into reverse you will hear and maybe feel it.

I'm not a transmission guy and there isn't any linkage to adjust but you can take off the top cover and look at it.

View attachment 911818

Awesome! I’ll take a look. Thank you!

 

[Valley Rock]

As in remove the dog house cover and shifter to see if there’s an issue there?

I think as in remove the dog house cover and the entire top of the trans, I think its like 12 or 15 bolts or so, then you can see the inner workings of the entire transmission and probably spot the problem, it may be something not too complicated that you could remedy with some ingenuity, but at least you'd know before removing the entire trans .

Edit: I drain it first to see what comes out, plus that way when you get the cover off you'll be able to see in there

 

[Milton1988]

I think as in remove the dog house cover and the entire top of the trans, I think its like 12 or 15 bolts or so, then you can see the inner workings of the entire transmission and probably spot the problem, it may be something not too complicated that you could remedy with some ingenuity, but at least you'd know before removing the entire trans .

Edit: I drain it first to see what comes out, plus that way when you get the cover off you'll be able to see in there

Thank you. I’ll do exactly this.

 

[Milton1988]

Hello everyone. Thanks for letting me in. I have a 1970 m813A1, and it seems as if I lost fifth gear. I adjusted the clutch a few days ago and now it won’t stay in 5th. Every other gear shifts and grabs just fine, but when shifting to 5th, it goes in, but as soon as I start to engage the clutch it kicks it right out of 5th. I tried double clutching, power shifting, shifting into 5th while the truck is sitting still, hi range, low range, and nothing.

My question is, before I Jimmy rig a chain hoist in the cab to lower the transmission out of it, is there anything I should check first? I don’t know much about the truck because I just bought it. I did notice once while messing around in low range that there was an air release “psst” sound while shifting between gears but that only happened a few times. Is that something that should be happening every time I shift? Should I change the fluid in the trans to see if it’ll help? Is there some sort of electronic device I should check that allows it to go into 5th? Also, other than that cross member being in the way, I think I can rig up some stuff to pull the tranny out myself. If so, how delicate is the process of just rebuilding it on my own? Is there a possibility that I can take the tranny apart and rebuild it while it’s still mounted on the truck? Any help and advice is greatly appreciated. I priced out a new rebuilt 6453 for 1900 + shipping and it’s something I can do, but before I go and spend 900$ on the freight shipping for a new one, I figured I’d ask here. Thank you!

UPDATE… installed a beefy battery disconnect. Before I’ve had a chance to crack her open, I fired her up earlier today to go for a short ride to the mail box and back, and as I was maneuvering to pull down the road, clutch pedal went all the way to the floor… so there’s that lol… figured I won’t mess with the adjustment on the linkage as it’s almost bottomed out to the max from the last adjustment. Good thing is that I already planned on replacing the clutch when I replace the tranny, so I guess I’ll be gathering all the parts over the winter and have a go at doing the clutch and tranny in the spring. I think I’m just going to order a rebuilt 6453 from eastern surplus along with all the parts to replace the clutch. I think I read on here something about using the right bolts for the flywheel or clutch plate, but I can’t find anything on it, so any advice on that would be appreciated. If anyone knows where I can order a full clutch rebuild kit that would be great as well. Cheers chaps!

 

[G744]

The sintered metal (Velvetouch) puck clutch is a better choice than the organic disk.

That is what I've found almost every 5-ton military rebuild.

 

[msgjd]

welcome to the fun ..

1: On all standard-tranny M-series 5-tons, you should always hear a brief "phsst" when shifting into reverse, and same again when you pull back into neutral .. Those are the only two movements that activate the poppet valve you will see on the tranny cover..

2: As others have said, the air has nothing to do with the tranny itself , the air is for only the transfer case (sprag)..

3: Being new to your 5T, never roll backwards in neutral nor forward gears .. Likewise, never roll forward in reverse. This
can cause damage to the sprag unit in the transfer case .. Think of it as something worse than running a pickup or
jeep locked in 4x4 on bare blacktop

4: As others have said, pop the top cover off and look in the tranny , feel around for play, wear, problems .. Wouldn't hurt
to check the drain plug for metal shavings, chips, pieces .. I have driven trucks where 5th gear would hold, but the gear
was worn enough the shifter pushed back at you when accelerating and moved forward when decelerating..

5: Since you lost your clutch pedal after adjusting it the 1st time, sounds like you have an issue with the T/O brg and
pressure plate fingers and will have to look in there again with a good light , with a Soldier B pushing on the pedal

6: Tranny cannot be rebuilt in-frame, but it drops down out of there easily enough without removing transfer case nor engine .. You just detach front driveshaft from the transfer case and push it out of the way to one side. Also take out the stub shaft between tranny and transfer case. You don't want to forget to unhook the clutch linkage nor the air lines near top of tranny.

 

[Milton1988]

welcome to the fun ..

1: On all standard-tranny M-series 5-tons, you should always hear a brief "phsst" when shifting into reverse, and same again when you pull back into neutral .. Those are the only two movements that activate the poppet valve you will see on the tranny cover..

2: As others have said, the air has nothing to do with the tranny itself , the air is for only the transfer case (sprag)..

3: Being new to your 5T, never roll backwards in neutral nor forward gears .. Likewise, never roll forward in reverse. This
can cause damage to the sprag unit in the transfer case .. Think of it as something worse than running a pickup or
jeep locked in 4x4 on bare blacktop

4: As others have said, pop the top cover off and look in the tranny , feel around for play, wear, problems .. Wouldn't hurt
to check the drain plug for metal shavings, chips, pieces .. I have driven trucks where 5th gear would hold, but the gear
was worn enough the shifter pushed back at you when accelerating and moved forward when decelerating..

5: Since you lost your clutch pedal after adjusting it the 1st time, sounds like you have an issue with the T/O brg and
pressure plate fingers and will have to look in there again with a good light , with a Soldier B pushing on the pedal

6: Tranny cannot be rebuilt in-frame, but it drops down out of there easily enough without removing transfer case nor engine .. You just detach front driveshaft from the transfer case and push it out of the way to one side. Also take out the stub shaft between tranny and transfer case. You don't want to forget to unhook the clutch linkage nor the air lines near top of tranny.

Thank you very much for the info! I’m gonna crack the top open here soon and have a look at the clutch. I’m pretty sure the clutch is cooked or bolts holding pressure plate came loose. That being said, I’ve started to make a parts list for everything I think I need. Please let me know if there’s something you would add or take away from this list. All that being said, I think it’s a job I can tackle with a friend or two in my driveway. Were no mechanics, but all have experience in doing related work on our jeeps for years from wheeling them. Everything is just bigger, heavier, and way more expensive.

New flywheel?
New pilot bearing
Clutch disc and pressure plate
Throw out bearing (greasable)
New bolts for pressure plate?
Clutch fork?
Alignment tool?
Spicer 6453 trans
Trans fluid?

Hopefully rear main isn’t leaking..

Can I leave the flywheel alone or should I pull it and have it checked or replace it?

can I reuse bolts for everything or should I get new ones?

torque specs?

should I blue loctite anything when reassembling?

what kind of fluid is best for trans?

where can I find the correct clutch alignment tool?

sorry for all the question and I know some of it should be basic knowledge, but I rather get the advice and info from people with first hand experience on this than having to do the job twice. Thanks again.

 

[msgjd]

Can I leave the flywheel alone or should I pull it and have it checked or replace it?

can I reuse bolts for everything or should I get new ones?

torque specs?

should I blue loctite anything when reassembling?

what kind of fluid is best for trans?

where can I find the correct clutch alignment tool?

1: Flywheel depends on what it looks like, of course.. It might already be a fairly-new flywheel with fairly-new clutch etc, and thus you might be the victim (as I have been) of a T/O bearing failure .. NOS mil-surplus bearings tend to be dried out, the grease leaks out sitting in the box on a shelf in a hot climate, or it hardens from age, thus the bearing fails prematurely .. The other problem is they say they are greasable, but the grease doesn't get into the actual bearing, only the sliding shaft part..

2: you should use new G8 bolts for the press plate, and if you remove the flywheel, same thing there ..

3: you should download the Maint and Op TMs on this site for your truck (M809-series) ..

4: I don't know if these torque values are exact same as in the TMs, but I have used these values on all 855 cummins I own , including the higher-HP turbocharged ones .. 30-35# on the press plate, criss-cross pattern starting with the bottom bolt .. Flywheel starts at 92#, then gradual torque pattern increments up to 184# .. Yes, flywheel has a torque pattern. as does the bellhousing, if you ever remove one. You can find these patterns online under 855 cummins info, perhaps in the TMs also..

5: never hurts to loctite any of those bolts , actually, it helps lube them at same time while torquing

6: required oil for tranny is on the truck's dash plate and in the TM .. There are certain GL numbers to avoid due to the yellow metals in the tranny and xfer case, plenty of discussion here on this site about that

7: I use a 1-3/4" OD 10-tooth tool , NAPA and many other places carry them .. Look online.. Sample part #AT-HT175

8: never have had to replace a clutch fork on these trucks

 

[msgjd]

 

[Milton1988]

1: Flywheel depends on what it looks like, of course.. It might already be a fairly-new flywheel with fairly-new clutch etc, and thus you might be the victim (as I have been) of a T/O bearing failure .. NOS mil-surplus bearings tend to be dried out, the grease leaks out sitting in the box on a shelf in a hot climate, or it hardens from age, thus the bearing fails prematurely .. The other problem is they say they are greasable, but the grease doesn't get into the actual bearing, only the sliding shaft part..

2: you should use new G8 bolts for the press plate, and if you remove the flywheel, same thing there ..

3: you should download the Maint and Op TMs on this site for your truck (M809-series) ..

4: I don't know if these torque values are exact same as in the TMs, but I have used these values on all 855 cummins I own , including the higher-HP turbocharged ones .. 30-35# on the press plate, criss-cross pattern starting with the bottom bolt .. Flywheel starts at 92#, then gradual torque pattern increments up to 184# .. Yes, flywheel has a torque pattern. as does the bellhousing, if you ever remove one. You can find these patterns online under 855 cummins info, perhaps in the TMs also..

5: never hurts to loctite any of those bolts , actually, it helps lube them at same time while torquing

6: required oil for tranny is on the truck's dash plate and in the TM .. There are certain GL numbers to avoid due to the yellow metals in the tranny and xfer case, plenty of discussion here on this site about that

7: I use a 1-3/4" OD 10-tooth tool , NAPA and many other places carry them .. Look online.. Sample part #AT-HT175

8: never have had to replace a clutch fork on these trucks

Thanks for everything. I’m getting all the parts together and then I’ll have a go at tearing her apart. That chain hoist in the cab is exactly what I had in mind and I’m glad to see that it works!

 

[US6x4]

This is another view of the same. It's such a sweet setup that I saved the pic for future reference.

 

[Milton1988]

This is another view of the same. It's such a sweet setup that I saved the pic for future reference.

View attachment 912266

I love the snatch block to make it easier to push the trans back! Awesome! I’m gonna do the same thing!