Tranny / tcase problem
 

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.

Re: Tranny / tcase problem
 

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
http://farm6.static.flickr.com/5244/...9d597bf8_b.jpg

Re: Tranny / tcase problem
 

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?

Re: Tranny / tcase problem
 

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.

Re: Tranny / tcase problem
 

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

Re: Tranny / tcase problem
 

Exactly.

Re: Tranny / tcase problem
 

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.

Re: Tranny / tcase problem
 

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

Re: Tranny / tcase problem
 

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.

Re: Tranny / tcase problem
 

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

Re: Tranny / tcase problem
 

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.

Re: Tranny / tcase problem
 

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

Re: Tranny / tcase problem
 

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.

http://farm6.static.flickr.com/5170/...067286ee_b.jpg

http://farm6.static.flickr.com/5290/...79130148_b.jpg

Re: Tranny / tcase problem
 

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

Re: Tranny / tcase problem
 

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!

Re: Tranny / tcase problem
 

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

Re: Tranny / tcase problem
 

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?

Re: Tranny / tcase problem
 

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!

Re: Tranny / tcase problem
 

I guess I won't remove it then.

Re: Tranny / tcase problem
 

:bsf:

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.

Re: Tranny / tcase problem
 

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

Re: Tranny / tcase problem
 

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.

Re: Tranny / tcase problem
 

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.

Re: Tranny / tcase problem
 

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

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

Re: Tranny / tcase problem
 

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

Re: Tranny / tcase problem
 

I still call BS. Voice of a lifetime of experience of 20ish year old guy on 1 single truck? I am sure that your 18” of lift, 40” tires, 468 BB and questionable engine and driveline angles as well driving habits through mud races may not have had anything to do with the transmission case breaking, right?

Sorry but I still harbor suspicion with you from THIS Pirate deal from a few years ago. Post #70 at Pirate. Once you play forum games like that it is hard to recoup yourself with guys older than you that still have good memories.

Re: Tranny / tcase problem
 

Interesting.

Re: Tranny / tcase problem
 

You are mistaken.

Re: Tranny / tcase problem
 

I might be reading this the wrong way, but doesn't that statement just prove what Larry's been saying all along? He shattered his trans case and that was with the frame attachment.

Maybe I haven't had enough beer yet.

Re: Tranny / tcase problem
 

Looks like we have a difference of opinion ,So lets hold the outside this forum battle down....

However My opinion mirrors Larry's . I run an 84 3/4 mudder 3 years racing in a bunch of pits around Kansas City . 350 turbo and a 205 transfer . No transfer brackets no rods from the mounts.

I beat on that thing hard , from the time the green flag dropped till i run out or the red flag was thrown I never lifted . No problems with adapters , No problem with transmission housings .

1 year and a 1/2 I run it as a long bed , Then as a short bed .

Re: Tranny / tcase problem
 

I will never ever use my truck that hard (I have others for that). I will still get a brace rod. I don't know why.

Re: Tranny / tcase problem
 

...

Re: Tranny / tcase problem
 

I've had plenty of beer but still confused by this

Re: Tranny / tcase problem
 

:metal: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

Re: Tranny / tcase problem
 

I'm dragging this back up for another question on NP205 support. Looking for Larry's advice on the matter, knowing his level of experience.

I clocked the 205 behind my Cummins/NV5600 flat with a Trail Tech Fab adapter. At the same time I ordered their NP205 support kit. It attaches to the rear of the case, opposite the front driveline and features a poly bushing. Any opinions on this means of support? It is closer to the center than a stock frame mount and does have a bushing.

Adapter (stock photo, mine is welded up and installed so no good pictures)
http://www.trailtechfab.com/gallery/...serialNumber=1


Support kit
http://www.trailtechfab.com/gallery/...serialNumber=1

I haven't welded up the support kit, so opinions are welcome.

Re: Tranny / tcase problem
 

My sm465 in my 71 doesn't have one, glad now, noticed it was missing but my engine is chained to the frame (with 3/4" slack) to help. Got to control the HP.

Re: Tranny / tcase problem
 

I'll be about 350 hp / 800 lb-ft once I finish turning up the Cummins. I've held back on playing with the pump until everything else is beefed up and this is one of the last things to do.

Re: Tranny / tcase problem
 

The last truck I built was a 454 4-speed with a later 205. Had 35" tires on it. I didn't beat the crap out of it, but gotta have some fun with a big block stick truck. That didn't have a brace on it. All the trucks I've owned, worked on, stripped parts off of in a junkyard, DIDN'T have that brace. Even with a small block, when you jump on it you can feel the drivetrain twist, shifter can move 3-4" maybe more. If you have that brace on there, the one piece is trying to hold the entire drivetrain from twisting. The t-case itself isn't gonna break, the wee little adapter is gonna take the force of it. I've had some 80s trucks with the 208 that had braces to went to the bell housing, but took them off and still didn't have a problem.

If you want to brace or add some support, that brace shown above would OK. Or some other type, but it needs bushings so it can flex with the rest of the drivetrain.

Re: Tranny / tcase problem
 

This thread is an interesting read. It is true that the T/C torque mount would be the cause of adapter and bellhousing failures.

I do see that some on here have said they weren't used on 73 and up trucks. I'm wondering about the validity of that statement only because my 73 K20 had the mount. Not to say that someone didn't add it on later, thinking it was necessary. I'm wondering when GM truly did stop using them.

Also, does anyone have a picture of what the alternative torque rod looks like? I've never seen this before.

Re: Tranny / tcase problem
 

It is always a good idea to know why you are doing something.