Tranny / tcase problem

[Farmstore34]

Hi all,
my friend has a '71 GMC K1500, 400 sbc, sm465 trans and 205 t-case. Yesterday, the housing between the tranny and t-case split wide open. The trans is still in place but the transfer case is barely hanging on (just by the side mount that bolts to the frame). Has anyone ever seen this before? Does anyone make a replacement housing? It is too dark for good pictures but it's a mess! Thanks for any input,
Colby.

[DirtyLarry]

Originally Posted by Farmstore34

the transfer case is barely hanging on (just by the side mount that bolts to the frame)

BINGO! When you replace the adapter do not use the frame bracket when you go back together. There is a reason GM quit using that side bracket. I have an old work colleague that retired a few years ago that was a GMC truck engineer from the late 60’s up until a couple years ago. He worked out of Pontiac Truck Product Center in Pontiac, MI. When I was doing my NV4500 swap last year being so many people here were wondering why I didn't add the side bracket. I asked him about that side bracket that was used on the early model 205’s and if I should add it and he said DO NOT use that bracket and if you have one take it OFF! It may have lasted 40 years but I wouldn’t use that side bracket going after you fix it. Chances are the adapter has been cracked for quite a while before it finally bombed out. That side bracket caused GM lots of problems back in the day with broken bellhousings and adapters on TH350 automatics and broken adapters on manual trans trucks, which is why the '73 and later trucks didn't have the tcase to frame bracket. Later 205’s didn’t even have the holes drilled and tapped.

I have a 465/205 adapter that you can have for free. Just pay the ride. This adapter is also from a ’71 or ’72 and must have had a small crack as it has been welded. I used it for 10 years without issues and became a shop ornament once I swapped in the NV4500. PM if you want it. I shipped a TH350/205 adapter a while back and the shipping was around $40. PM if you are interested and I’ll get you some pictures of the weld job.

'78....no holes drilled in the tcase

[1malo68]

I'm confused! what is it that causes the torque bracket to put more stress on the tailhousing. The only thing I can think of is if you had a broken motor mount or something. Please help me understand this. Frame flex?

[DirtyLarry]

Originally Posted by 1malo68

I'm confused! what is it that causes the torque bracket to put more stress on the tailhousing. The only thing I can think of is if you had a broken motor mount or something. Please help me understand this. Frame flex?

Torsional stress. The engine naturally wants to lift up and twist when under load (even with good engine mounts) then you have the tcase tied to the frame on the passenger’s side. Something in between is going to eventually break. GM later tied the aluminum transfercases (and some 205s) to the bellhousing by way of a long strut rod instead of tying it to the frame, which is fine. Bolting the transfercase to the frame was a bad idea.

[jaros44sr]

Thanks for the info dirty larry, never heard that before....just another day of learning hanging around

[Redcap]

Originally Posted by DirtyLarry

Torsional stress. The engine naturally wants to lift up and twist when under load (even with good engine mounts) then you have the tcase tied to the frame on the passenger’s side. Something in between is going to eventually break. GM later tied the aluminum transfercases (and some 205s) to the bellhousing by way of a long strut rod instead of tying it to the frame, which is fine. Bolting the transfercase to the frame was a bad idea.

Exactly.

[BLAZERMAN]

I'm guilty of this myself...I had no trouble or leaks till I replaced my soft worn rubber transmission and transfer case mounts with poly, allowing virtually no movement at all. It didnt take long to develop a nasty leak from a crack in the adapter.

[Dirt_Diver_Jr]

DirtyLarry,
I am new to this forum and also to trucks predating the 2000s. I also realize this post is ten years old at this point butttt... I have recently redone my drivetrain. 69 Chevy with a 350, SM465, NP205. Im putting it all back in now and wanted to replace the rubber in the mount on the side of the Tcase-Frame. I have now read through multiple threads on here arguing wether to use this or not. I hear your argument to not use the mount but I see in your photo that you have a crossmember that runs under both your trans and your tcase. I only have a crossmember under the trans. This means that if I don't use the frame mount with my Tcase the only thing holding my 205 in there would be the 8 bolts to the spacer. Is it okay to have the Tcase hanging there in space by only the eight bolts? Suggestions? Thanks!

['63GENIII]

IIRC, there is also a rod (for lack of a better description) that attaches to the side of the T Case and ties into the back of the block at one of the bell housing bolts. This should give some support to the T case while allowing the engine, transmission and transfer case to move as one which takes the stress off of the bell housing and the trans to T case adapter.

FWIW, I run a divorced 205 and have not had to deal with the issues that you are asking about but have read much of the arguments for and against the side mount. If I were to run a married set up as you are, I'd run the rod support and ditch the side mount. Just my .02$.

[Richard2112]

I don't even have 4wd and yet learned something new from reading this thread. I was going to attach a second cross member to my NV4500 and folks said not to. So, I didn't. Now I see why.

[mud.man.rj]

Do the 205's run the rod, thought it was only the 203 cast or the 208, 205 has the side mount, I would run the mount if it came w it or make the rod work as mentioned, less stress on it for sure especially if the tire size is increased over stock or abused like I do, I call it driving it, haha.
Mudman.

[El Dorado Jim]

Originally Posted by Dirt_Diver_Jr

DirtyLarry,
I am new to this forum and also to trucks predating the 2000s. I also realize this post is ten years old at this point butttt... I have recently redone my drivetrain. 69 Chevy with a 350, SM465, NP205. Im putting it all back in now and wanted to replace the rubber in the mount on the side of the Tcase-Frame. I have now read through multiple threads on here arguing wether to use this or not. I hear your argument to not use the mount but I see in your photo that you have a crossmember that runs under both your trans and your tcase. I only have a crossmember under the trans. This means that if I don't use the frame mount with my Tcase the only thing holding my 205 in there would be the 8 bolts to the spacer. Is it okay to have the Tcase hanging there in space by only the eight bolts? Suggestions? Thanks!

Yes you will be fine just using the crossmember with the adapter bolted to it,that is the way they came from about 1973 on up, no side mount

[Aggie-01]

I know this is an old thread but I have a 1973 Jimmy with a NP203. It is leaking from the rear bolt on the torque bracket that is being discussed. Is there a seal behind the bolts? Also I know the main discussion was on the NP205 but would it be appropriate to remove the torque bracket on mine as well?

[Redcap]

Originally Posted by Aggie-01

I know this is an old thread but I have a 1973 Jimmy with a NP203. It is leaking from the rear bolt on the torque bracket that is being discussed. Is there a seal behind the bolts? Also I know the main discussion was on the NP205 but would it be appropriate to remove the torque bracket on mine as well?

Nope. Pull the bolt and seal the threads. Or remove the bracket entirely.

[Mt Man Chad]

This is some good info!
I just placed a NP205 in my 68 burb and was about to drill new holes in the frame for the mount.
The truck original came with a NP203 and the mount is in a different location along the frame = 4 less holes to drill and less parts to deal with.

[1malo68]

Hey Larry;
Did you fab up a rod or something that ties the transfer case to the bellhousing for extra support or is it OK not to have anything other than the mounts on the crossmember? Opinions?
Thanks

[DirtyLarry]

Originally Posted by 1malo68

Hey Larry;
Did you fab up a rod or something that ties the transfer case to the bellhousing for extra support or is it OK not to have anything other than the mounts on the crossmember? Opinions?
Thanks

I didn’t add any supports to my 205 when I did the NV4500 swap last year. The tcase just hangs there by the adapter plate just like stock. My other bone stock K20 with a stock SM465/205 doesn’t have anything supporting it either. It hangs by the adapter too. The only ones that had the support rod from the tcase to the bellhousing were mainly automatics and even at that, not all had them.

[bmchevy1979]

Originally Posted by DirtyLarry

The only ones that had the support rod from the tcase to the bellhousing were mainly automatics and even at that, not all had them.

I agree because my blazer only has the brace from the motor mount pad (block side) to the bellhousing nothing for the transfer case

[Yukon Jack]

What an interesting thread - when I swapped in an NP205 into my 70 Blazer in place of the broken Dana 20, the side bracket didn't fit and I've been meaning to get around to modifying it or making a new one - now I can forget about doing that. Procrastination paid off!

[jaros44sr]

Yukon, that is funny....procrastination pays off, maybe not, ill want till tomorrow to find out

[1972RedNeck]

I've got a 700R4 in my '72 K2500. It only has 4 bolts holding the adapter on the transmission. Will that be sufficient to hold it without the side bracket or do I need a brace rod from the bell housing?

[Chevy1TonFun]

Originally Posted by 1972RedNeck

I've got a 700R4 in my '72 K2500. It only has 4 bolts holding the adapter on the transmission. Will that be sufficient to hold it without the side bracket or do I need a brace rod from the bell housing?

If you do not have the bracket that connects the side of the t-case to the frame you will shatter your trans housing! This is a must!

[1972RedNeck]

Originally Posted by Chevy1TonFun

If you do not have the bracket that connects the side of the t-case to the frame you will shatter your trans housing! This is a must!

I guess I won't remove it then.

[DirtyLarry]

Originally Posted by Chevy1TonFun

If you do not have the bracket that connects the side of the t-case to the frame you will shatter your trans housing! This is a must!

No way. The side bracket creates more problems that it saves, which is why GM quit using on trucks build after ‘72. That is information straight from a retired GM truck engineer. The support rod between the tcase and trans bellhousing is not a bad idea to add but still not required.

[mud slut 350]

Originally Posted by DirtyLarry

No way. The side bracket creates more problems that it saves, which is why GM quit using on trucks build after ‘72. That is information straight from a retired GM truck engineer. The support rod between the tcase and trans bellhousing is not a bad idea to add but still not required.

Aggreed. on all my K5s that ive had and the k10 i have now never had ANY braces from the t case. Thought about puttin that bar back on when i added the 465 but never got around to it never had any problems with any of them. Then need to flex.

QUOTE: DirtyLarry you can call BS, but this is the voice of experience. I shatter my trans casing and that was with the frame attachment. I was just giving my two cents.

Thats why it broke there was no give between engine, trans, and tcase with ur t case tied to the frame so it gave way at the weakest link a.k.a that adapter with the 4 bolts to the trans without it being tied to the frame the eng trans and t case torque as a whole on the engine and trans mounts. think about it this way. you have a peice of paper write engine on one end, trans in the middle and tcase on the end. grab each end and pull it kinda snug twist the side with the engine written on it simulating torque from the engine, and leave the t case side still simulating it being bolted to the frame. Where does the twisting occure? in the middle or the "trans". now that same peice of paper twist again and let the t case side twist with the engine side simulating it being on rubber bushings and theres no stree in the middle. All the stress goes to the eng mounts and the trans mounts once they bottom out the bushings and set on the solid frame. Now nothing can flex any more than something else its all one solid peice. Hope it helps ya get the picture 1 ton