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.

[1malo68]

Thanks Larry! It makes sense to me now and Blazerman just confirmed it!

[OrrieG]

Thanks for the info guys, looks like I will be removing the bracket I fabbed because I thought it was missing. My drive train came out of a 74, xfer had the holes drilled and tapped. I drove it for 15 years without one with no problems (did have the engine chained to the frame on drivers side to limit torque) but thought I would make it "correct" this time.

[eric67m]

That bracket/mount also has rubber bushings? My truck did not have one but I added one during my"rebuild". Sounds like maybe I should take it off....
Posted via Mobile Device

[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.

[1972RedNeck]

What year vehicle should I look for in the junk yard? I'll get the brace rod just to be safe.

[DirtyLarry]

Originally Posted by 1972RedNeck

What year vehicle should I look for in the junk yard? I'll get the brace rod just to be safe.

What tcase do you have behind the 700R4? 205’s didn’t come behind 700R4’s so you have to modify one to fit. Some 70’s and 80’s trucks had them. Just walk the junk yard until you find one. You’re probably going to need to modify whatever you find anyway. You really don’t need the rod unless it makes you feel better to have one anyway. I never ran a support rod or tcase side bracket on any of my old 4x4’s and never had an issue without them.

[Chevy1TonFun]

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.

[1972RedNeck]

Originally Posted by DirtyLarry

What tcase do you have behind the 700R4? 205’s didn’t come behind 700R4’s so you have to modify one to fit. Some 70’s and 80’s trucks had them. Just walk the junk yard until you find one. You’re probably going to need to modify whatever you find anyway. You really don’t need the rod unless it makes you feel better to have one anyway. I never ran a support rod or tcase side bracket on any of my old 4x4’s and never had an issue without them.

I have a 205. I am fine with having to modify something.

Originally Posted by Chevy1TonFun

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.

So should I leave the side bracket on or take it off? I am confused.

[yousesteers]

The frame bracket does not allow the transfer case to flex and thus either breaking the case or the adapter most usually if it were mine i would get rid of it