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Old 10-26-2011, 11:09 PM   #1
Farmstore34
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Question 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.
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Old 10-27-2011, 01:18 AM   #2
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Re: Tranny / tcase problem

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Originally Posted by Farmstore34 View Post
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 60ís 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 205ís 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 wouldnít 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 205ís didnít 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 í71 or í72 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 Iíll get you some pictures of the weld job.

'78....no holes drilled in the tcase
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Old 10-27-2011, 04:18 AM   #3
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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?
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Old 10-27-2011, 11:35 AM   #4
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Re: Tranny / tcase problem

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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 passengerís 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.
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Old 10-27-2011, 06:19 PM   #5
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Re: Tranny / tcase problem

Thanks for the info dirty larry, never heard that before....just another day of learning hanging around
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Old 10-27-2011, 08:17 PM   #6
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Re: Tranny / tcase problem

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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 passengerís 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.
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Old 10-27-2011, 11:07 PM   #7
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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.
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Old 10-28-2011, 05:49 AM   #8
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Re: Tranny / tcase problem

Thanks Larry! It makes sense to me now and Blazerman just confirmed it!
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Old 11-10-2011, 02:05 PM   #9
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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.
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Old 11-10-2011, 05:17 PM   #10
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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....
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Old 11-11-2011, 07:03 PM   #11
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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.
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Old 11-11-2011, 07:55 PM   #12
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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
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Old 11-11-2011, 08:38 PM   #13
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Re: Tranny / tcase problem

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Originally Posted by 1malo68 View Post
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 didnít 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 doesnít 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.



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Old 11-12-2011, 12:41 PM   #14
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Re: Tranny / tcase problem

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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
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Old 11-14-2011, 02:51 PM   #15
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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!
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Old 11-14-2011, 04:32 PM   #16
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Re: Tranny / tcase problem

Yukon, that is funny....procrastination pays off, maybe not, ill want till tomorrow to find out
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Old 12-22-2011, 11:37 PM   #17
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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?
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Old 12-23-2011, 08:18 AM   #18
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Re: Tranny / tcase problem

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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!
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Old 12-23-2011, 11:49 AM   #19
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Re: Tranny / tcase problem

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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.
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Old 12-23-2011, 11:55 AM   #20
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Re: Tranny / tcase problem

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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 Ď72. 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.
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Old 12-23-2011, 03:20 PM   #21
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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.
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Old 12-23-2011, 03:49 PM   #22
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Re: Tranny / tcase problem

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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? 205ís didnít come behind 700R4ís so you have to modify one to fit. Some 70ís and 80ís trucks had them. Just walk the junk yard until you find one. Youíre probably going to need to modify whatever you find anyway. You really donít 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 4x4ís and never had an issue without them.
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Old 12-23-2011, 07:15 PM   #23
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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.
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Old 12-23-2011, 08:39 PM   #24
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Re: Tranny / tcase problem

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What tcase do you have behind the 700R4? 205ís didnít come behind 700R4ís so you have to modify one to fit. Some 70ís and 80ís trucks had them. Just walk the junk yard until you find one. Youíre probably going to need to modify whatever you find anyway. You really donít 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 4x4ís and never had an issue without them.
I have a 205. I am fine with having to modify something.

Quote:
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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.
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Old 12-23-2011, 09:21 PM   #25
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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
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