Cracked a TH400 case and support brackets with a NP205

[Kaiserjeeps]

I see others have had this same problem. I did not see my answer though. I had a cracked TH400 case about 6 inches forward of the tail end of the trans case tail end. Mine cracked all the way around and was dumping ATF all over. I run a NP205 transfer case now with a fixed yoke after the weld repair. I found rotten jellied mounts under the adapter and that probably contributed to excess bouncing and stress on the trans case. I had a guy weld up the TH400 case and he did a good job. Turns out that the CUCV trans case is a heavy duty version and he could not find one so he welded it up. I replaced everything with new mounts and so far so good. Now I want to put in my 4L80E. It seems to me that a 205 is pretty heavy to attach to a aluminum transmission case without anything supporting it other than the mounts under the adapter. The trans guy said I should have support rods going to the transfer case. That they attach to the trans case up at the bellhousing. I have never heard of this nor do I see a spot for it. I live miles up a bumpy dirt road. I don't want the same thing to happen to my 4L80E case. Has anyone heard of or done any additional supporting of the 205 case? Are there factory support pieces out there somewhere from a different application? I am considering fabbing up my own mounting system.

 

[Chaski]

On the passenger side of your transfer case there should be two large threaded holes (about 5/8" dia). On every 73-87 4x4 Chevy besides yours there is a big steel rod bolted to the transfer case there up to the bellhousing.

You should be able to go to a pick-n-pull wrecking yard and harvest one for cheap.

 

[porkysplace]

On the gas motors the rods went from the transfer case to the motor mounts I have a set in one of my parts piles , I don't know if they will work with a diesel.

 

[Kaiserjeeps]

Well I finally found what you guys are mentioning in Bing images. There was a lot of home made stuff like independent mounts made of angle iron and a couple bushings on the frame. But I did finally find two photos of the rod. I would think keeping it attached to the trans or motor would be better than the frame. It would move as one unit that way. And not wanting to hold the 205 firmly at the frame while the motor torque does it's thing causing some twist. So I see I am at risk of breaking the case again unless I get something on there soon. I want to save this transmission as it functions well. So I will be making two of them. One for this TH400 and a longer one for the 4l80E. I am also glad I asked because I want to get my new exhaust system on and it will go right past the rod. I did see two shorter rods that look like they attach to the lower cover over the torque converter.
A forestry dept swapped in the 205 for the PTO feature. They ran a hydraulic pump with it. Looks like they forgot a very important piece in the swap.
Thanks guys for responding and setting it straight. I don't want to break the truck again. Time to fire up the welder.

 

[porkysplace]

Well I finally found what you guys are mentioning in Bing images. There was a lot of home made stuff like independent mounts made of angle iron and a couple bushings on the frame. But I did finally find two photos of the rod. I would think keeping it attached to the trans or motor would be better than the frame. It would move as one unit that way. And not wanting to hold the 205 firmly at the frame while the motor torque does it's thing causing some twist. So I see I am at risk of breaking the case again unless I get something on there soon. I want to save this transmission as it functions well. So I will be making two of them. One for this TH400 and a longer one for the 4l80E. I am also glad I asked because I want to get my new exhaust system on and it will go right past the rod. I did see two shorter rods that look like they attach to the lower cover over the torque converter.
A forestry dept swapped in the 205 for the PTO feature. They ran a hydraulic pump with it. Looks like they forgot a very important piece in the swap.
Thanks guys for responding and setting it straight. I don't want to break the truck again. Time to fire up the welder.

On the gas motors the short rods go from the motor mount to the inspection cover for the torque converter. There is a tab on the part of the motor mount that bolts to the motor .

 

[gimpyrobb]

Post the pics you found Al, so that this thread can educate others!

 

[Kaiserjeeps]

Yes! Good Idea Chris. Here is one with it unbolted off the transfer case. Note the HD in the TH-400 case. Heavy Duty.




And one installed correctly but not tight.



I saw this and while it probably helps, it causes separate flexing from the engine and trans with engine torque flex. The frame is going to want to hold it still while the minor movement from the engine and trans will fight this. Probably best to keep everything as one by using the rod to trans bell.



I'm going to pick up some solid rod on Tuesday and get enough for two of them. Rather than remake the rod after the 4L80E install.
This board has been educational and a great help over the years.

 

[acmunro]

I always think it is strange the CUCV trucks did not have these but the civilian trucks did.

 

[gimpyrobb]

Once it gets up in the double digit temperatures(5* right now), I'll have to crawl under my 6.5 chevy and see if the rods that go to the T-case are there.

 

[Skinny]

I remember reading that GM no longer used them because it promoted cracking.

 

[dstang97]

http://diy4x.com/product.php?productid=17683

 

[rustystud]

I remember reading that GM no longer used them because it promoted cracking.

Actually it was cost. They worked great but since GM went with the heavy duty case on most off road 4X4 trucks they felt they could get away without it.

 

[Kaiserjeeps]

I was just getting ready to make a rod from a piece of 5/8ths. But for 55 bucks that extra support looks fantastic. I just may spring for it. Thanks for posting!

 

[dstang97]

I was just getting ready to make a rod from a piece of 5/8ths. But for 55 bucks that extra support looks fantastic. I just may spring for it. Thanks for posting!

I have seen complete kits already made check out these sites. I use these guys all the time

diy4x
offroaddesign
ruffstuffspecities

 

[Kaiserjeeps]

I looked at all those sites. Great stuff and some of it was pretty reasonable. I am going to make the rod and use the rear NP205 round rear cover mount from DIY4x with an extra frame cross member I found in my piles of parts. I may make the crossmember from something smaller but it looks like the way to go. Those two extras should keep the trans case intact even with hard use. I am taking my 4L80E in next week for rebuilding. When the mounts and new trans install are all said and done I will post up.

 

[reaper556]

Does anyone have pic of the rod that would be used on a truck with a np208 or would it be the same as the one shown for the 205?

 

[stanzuray]

Today was a good day. After more than a year looking for a TH400 to 205 transfer case adapter found and bought one on Hillbilly Wizard (figure 8 one). They are aftermarket and aluminum and supposedly stronger than the original which are very rare due to many breaking. I also cracked the rear of the TH400 more than 180 degrees around in the same accident (huge pothole) and have been limping along ever since. Found a great HD case, 2 support rods for the flywheel cover to engine and long support rod from engine to transfer case. While the rods are helpful, especially the long one, the thing that really supports the weight of the transfer case is an extra actual cross member that pushes up slightly on the underside of the transfer case. When I put this on it actually closed the crack up and been hauling wood and fish and driving for over a year very carefully. When I put all the new stuff on soon I'm making a permanent cross member a priority. The one I have has rubber between it and the transfer case and nothing connecting the two but light pressure so the engine torques around freely. The fact this has held up and the crack hasn't gotten any bigger has me sold on this idea (opens up a good 1/8" and leaks bad when transfer case doesn't have support cross member on it). Always open to ideas why it wouldn't work though. Stan

 

[rustystud]

Today was a good day. After more than a year looking for a TH400 to 205 transfer case adapter found and bought one on Hillbilly Wizard (figure 8 one). They are aftermarket and aluminum and supposedly stronger than the original which are very rare due to many breaking. I also cracked the rear of the TH400 more than 180 degrees around in the same accident (huge pothole) and have been limping along ever since. Found a great HD case, 2 support rods for the flywheel cover to engine and long support rod from engine to transfer case. While the rods are helpful, especially the long one, the thing that really supports the weight of the transfer case is an extra actual cross member that pushes up slightly on the underside of the transfer case. When I put this on it actually closed the crack up and been hauling wood and fish and driving for over a year very carefully. When I put all the new stuff on soon I'm making a permanent cross member a priority. The one I have has rubber between it and the transfer case and nothing connecting the two but light pressure so the engine torques around freely. The fact this has held up and the crack hasn't gotten any bigger has me sold on this idea (opens up a good 1/8" and leaks bad when transfer case doesn't have support cross member on it). Always open to ideas why it wouldn't work though. Stan

I believe this support is from "Trail Tech Fab .com" . Looks to be a pretty good design.

 

[stanzuray]

Rusty
So you would not put this mount in the same department as those frame mounts that people say held the transfer case too firm and actually added to the problem of broken transfer case mounts or rear transmission cracks. Is it because it flexes enough. If so I'll get one as they don't stick down any below the transfer case like what I have been using. Thanks - you're a gold mine of knowledge. Stan

 

[rustystud]

Rusty
So you would not put this mount in the same department as those frame mounts that people say held the transfer case too firm and actually added to the problem of broken transfer case mounts or rear transmission cracks. Is it because it flexes enough. If so I'll get one as they don't stick down any below the transfer case like what I have been using. Thanks - you're a gold mine of knowledge. Stan

When you use this one, it actually will be mounted at or near the center line of the truck. Since it is a large rubber mount it will have a lot of flex. Just imagine your fist with a 3 foot rod in it and twist it. Your fist is not moving much but the ends of the rod will be over 90 degrees in moments. Same thing here. It's when they put the mounts along side the transfer-case that causes the problems. It is not allowed to flex, so what does flex is the mounting itself. If you go with this style of mount you can leave out the factory mount. Also use the transmission to transfer-case rod and the two engine to transmission rods. That set-up will give you a good "3 point" power plant mounting system. Or just stay with the "stock" system along with the three support rods.

I should add that I just use the "factory" mount myself. Though I went with Polyurathane instead of the rubber mount. I also use the "factory" transmission to transfer-case rod and the two engine to transmission rods. It has worked great on and off road now for years. Though I don't rock crawl anymore. More of just driving through the woods and old logging trails now a days.