Questions before I order a rebuilt TH400

[stanzuray]

Got a 1986 M1031 with the TH400 and 205 transfer case. Cracked the tranny main body up high (driving in some crazy ruts and mud holes) and it now allows the crack to open/close slightly when I ran truck in 2 wheel drive on jack stands. Except for vibration now all runs fine and no fluid loss so far. So some


questions and have been all over site looking at tranny type options and rebuild hints etc. and still unsure about a few things.

1. Is welding out of the question. Bolt head is broke off and could ez out and replace. Don't like the way it is cracked to steel plug hole and don't want a weaker case when done.
2. Will have to get one from out in the city and flown in so will have anything but a perfect tranny rebuilt before shipping in but need to know if there are any things to watch for like different TH400 models. Seems from all my reading that there are two things some say are issues: a. get a TH400 case with an HD on the top side. b. make sure it's a 4x4 or a "long neck end" TH400 and not the shorter ones used in some 2x4 vehicles.
3. Any other things to do or watch for to get the right one.
Don't have the luxury of getting a wrong one and being able to return it as the costs to ship are as much as the tranny - plus the costs of having an unusable one rebuilt. Live in a village not connected to the road system - all gravel/dirt roads here.
So thank you for helping me with my baby. Bad time of year to have it happen. Stan

 

[cucvrus]

That is a common place to break. I have seen the transmissions with the HD like most but also many without the HD. Side by side I see no real noticeable difference. That truck was probably lifted from the side with a loader or forklift and that did the initial damage and started the crack. I have been on very rough roads and jumps and not broken one off. The used cases are getting hard to find. At the point yours is in I would say you have the option to weld it. I have a few transmission cases but that would be very costly to ship.These cases have seen the wrath of lifting with a loader. Like I said I have seen many with the same crack. Not very HD in my eyes. Very weak at the tail end on the stock TH 400. There may be something you can do to add some support to the weight of the transfer case hanging back there. I see stock trucks with a support rod going up to the motor mount for support. Cannot figure out why that never applied to these CUCV's. Good Luck. If I could help out I would.

 

[MarcusOReallyus]

Best bet is to find a local trans rebuilding shop that has a good reputation. Online sources are sketchy. For example, I have seen a ton of horror stories about Monster. Bad parts, bad service, not owning up to problems.

 

[Hasdrubal]

I understood the military left out the support rods because it would add another couple of shekels to the contract price for each truck. Easier to get the motor pool to replace the odd tranny if it cracks. When I got my M1009, guy told me I had to have these or the torque from the diesel could break the tail end of tranny. He had them on his M1008, so I measured them, there are 3, went to a GM truck wrecker and source them. There are quite a few different lengths GM made, I couldn't find the correct length for 2 of the shorter braces, so he cut and re-welded them for me. There's a thread on here somewhere where I posted pics of the braces if you're interested.

 

[stanzuray]

I understood the military left out the support rods because it would add another couple of shekels to the contract price for each truck. Easier to get the motor pool to replace the odd tranny if it cracks. When I got my M1009, guy told me I had to have these or the torque from the diesel could break the tail end of tranny. He had them on his M1008, so I measured them, there are 3, went to a GM truck wrecker and source them. There are quite a few different lengths GM made, I couldn't find the correct length for 2 of the shorter braces, so he cut and re-welded them for me. There's a thread on here somewhere where I posted pics of the braces if you're interested.

Called a tranny shop in the city and may get a core they have rebuilt. They mentioned the rods also (of which I have none on mine). Also mentioned the valve bodies are different in the diesel mated engines so may have to send mine in so they can get parts off it. I'll look up the post you mentioned. I could make them if I have to but will get them regardless. Send the thread link if you got it. Thanks - these replies are just the direction and specifics help I needed. Thanks Stan

 

[cucvrus]

I just pulled a 700R out of an 87 K10 and it had all the rods that we speak of. I have another pair. I was thinking about adding the bars to my Terminus M1009. I have them why not use them. I could measure them and advise you of the length and size. Not sure how that is going to work out. I have not studied the motor mounting issue very closely. I just removed them when I removed the transmission and transfer case. Let me know. I see you have the transmission out.

 

[sschaefer3]

I found the rods on eBay, they show up there from time to time.

 

[Hasdrubal]

Pics here ; http://www.steelsoldiers.com/showthread.php?142732-No-engine-to-bell-housing-support&highlight=

 

[rustystud]

The HD case is "thicker" then the standard case. I have actually cut them open to verify this. Also the clutch packs will be bigger. Meaning they will be "5"clutch packs instead of "4" . Do you have the aluminum torque converter cover ? That is a good thing to have. It has provisions for brace rods to the engines motor mounts. The HD case will come with the bolt holes already in for this.

 

[rustystud]

Here are some pictures showing what I mean. The first two show the HD cover with support rods. the third shows the case and how it's already drilled and tapped for the HD cover. The fourth picture shows the 8 bolt holes for mounting the pump housing. Standard units have only 6 or sometimes 7 bolts. The last picture shows the case number. Any case that has "raised" numbers is a HD case. I've seen them numbered from 38 to 45. I'm sure there are more.

 

[stanzuray]

First thing I say is when I get the rebuilt transmission the truck ain't getting used till the 3 support rods are installed and the transfer case to cross member plate/brace is in also. I found an old civilian 4x4 in town here with braces and a plate all installed. They probably don't fit as engine and transmission are different but I may be able adjust/modify them if I can't find real ones. This isn't the first troubles I've had because of things not on the truck.
CUCVUS - I'll get with you on the rod measurements if I can't find real ones. Seems from the pictures/link HASDRUBAL posted, there are 2 rods from the motor mounts to the flywheel inspection cover (which I still want from you) and a single heavy rod from somewhere to the transfer case side. Thanks HASDRUBAL.
RUSTYSTUD - appreciate the info on the thickness of the HD cases - I'll make sure to get one of those cases.
Hopefully I can get this done before I have to move to fishcamp. Truck was suppose to be my main driver for all the summer/fall work coming up. Thanks everyone. Stan
Also just got your last posted pictures on the braces and trans case - that clears up a lot. Getting to be an expert thanks.

 

[stanzuray]

Just got them - great pictures