Transmission case broke....again.

[johnnywagon]

I've been told that this isn't uncommon? Twice now I have completely cracked the case all the way around the tail shaft on a turbo 350 in a 71 Blazer. Someone mentioned a heavier duty K-Case? for the trans. Also heard about some extra bracing around the t-case?

It is a lame design how the trans is only supported by hanging between the motor and transfer case.

I was thinking of building a cross-member for an actual trans mount or even a cradle to connect the motor to the trans to the t-case.

Someone suggested I loosen some of the t-case crossmember bolts to allow for flex?? Really?

Any ideas and/or pictures would be greatly appreciated!!

[special-K]

There`s nothing lame about how the transmission is mounted.I`ve seen what you do and can see how it breaks .Not ragging on ya.I love wheelin`hard.But,stuff breaks when I take it beyond what it`s designed for.I don`t think a K-case would be any better.The cast aluminum can only take so much.And,the more rigid you mount it the sooner it will break.You need some cast iron in there,IMO.Get a 4spd.Remember,automatics started off as a convenience item for mild mannered people driving around town.They only just started putting them in 4wds when the Blazer was introduced.Back then the mind set was it ain`t a truck unless it`s a manual.

[OrrieG]

350TH are notorius for cracking when the engine moves because of torque, especially when you get off and on it hard. Transmission is restrained at the back by the mount and weight of the transfercase, engine moves and bang goes the aluminum case, usually across the bell portion around the fluid inlet lines. Solution is to fit a mount (chain, cable or slotted bracket) on drivers side that allows normal (1" or so) movement but stops rotation when the engine accelerates and rotates.

[70 beast]

here is the last auto i owned....proud to say i own nothing but manual trucks

[munger]

[special-K]

Originally Posted by special-K

...Not ragging on ya.I love wheelin`hard.But,stuff breaks when I take it beyond what it`s designed for.I don`t think a K-case would be any better...

I busted the TH400 K-case in my`84 K/30,so I don`t have room to talk.I was very hard on that truck.

[OLDCHEV4X4]

I broke a TH350 around the tail shaft on my 72 Blazer. I put in a DIY engine crossmember, new bushings for the TC torque mount, new mounts at the adapter, and i made a turnbuckle with heim joints to go from the cylinder head down to the frame. So far so good. Its been in there about 2 yrs.

[wildwilly4x4]

The 205/th350 combos in the later 70's have a solid rod brace that goes from the 2 BIG bolt holes on the passenger side of the t-case up to one of the bellhousing bolts at the motor to help combat this problem. I had this happen alot in my 1 ton '80 blazer before I swapped it for a 400/205. Make sure you use NEW high quality mounts at your motor and t-case. I went to polyurethane mounts, but I'm sure you can use good quality OEM mounts with good results. Dont forget your body mounts too. In my opinion the body mounts are just as important as your motor and tranny mounts. As body mounts wear out they actually allow your frame to flex more than it did when you first start wheeling these things, thats my opinion of why you kind of just "all the sudden" start cracking the housings out. Alot of my wheeling buddies have made stout cradles from steel the tie the 4 rear bolts to a couple of the bellhousing bolts with good results. You may also think about boxing your frame if you are wheeling it pretty hard. Good luck!

[johnnywagon]

Originally Posted by OLDCHEV4X4

I broke a TH350 around the tail shaft on my 72 Blazer. I put in a DIY engine crossmember, new bushings for the TC torque mount, new mounts at the adapter, and i made a turnbuckle with heim joints to go from the cylinder head down to the frame. So far so good. Its been in there about 2 yrs.

I've been looking at the DIY4X crossmenber and yes all new poly mounts and an engine torque strap for sure! Thanks!!

[johnnywagon]

Originally Posted by wildwilly4x4

The 205/th350 combos in the later 70's have a solid rod brace that goes from the 2 BIG bolt holes on the passenger side of the t-case up to one of the bellhousing bolts at the motor to help combat this problem. I had this happen alot in my 1 ton '80 blazer before I swapped it for a 400/205. Make sure you use NEW high quality mounts at your motor and t-case. I went to polyurethane mounts, but I'm sure you can use good quality OEM mounts with good results. Dont forget your body mounts too. In my opinion the body mounts are just as important as your motor and tranny mounts. As body mounts wear out they actually allow your frame to flex more than it did when you first start wheeling these things, thats my opinion of why you kind of just "all the sudden" start cracking the housings out. Alot of my wheeling buddies have made stout cradles from steel the tie the 4 rear bolts to a couple of the bellhousing bolts with good results. You may also think about boxing your frame if you are wheeling it pretty hard. Good luck!

Thanks Willy, Im on the same page with you on everything here. My truck has a 3" "plastic" body lift installed by the P.O. I hate it but Im stuck with it and I know how much the frame flexs because of it (and maybe how I drive it). One day steel crossmembers and spacers will replace the "plastic" body lift.

[racin69z]

Do you have the brace that uses the two holes on the passenger side of the transfer case? We broke a couple of cases in Mom's blazer until we put that brace on. Its been through 3 years in a 700 hp mud truck with no more breakage since.

[Burt4x4]

Oopps!
I never have wheeled a slush box rig before..me like SM465
I don't think looseing the crossmember for flex is a good idea at all
Good Luck

[johnnywagon]

Originally Posted by Burt4x4

Oopps!
I never have wheeled a slush box rig before..me like SM465
I don't think looseing the crossmember for flex is a good idea at all
Good Luck

I agree, dont wanna loosen things up for sure. Building a transmission cradle, I should have some pix by tomorrow night!

[johnnywagon]

Transmission cradle.....OVERKILL!

......still not done yet.

[63chevyll]

wow dude, overkill is right, but a good idea. good thing you have room with that body lift.

and if it helps, ive broken 2 TH350 Cases in a 2wd before........getting traction always brings other problems

[70 beast]

overkill...yes. but it looks like itll fix the problem....or atleast this one.

[y5mgisi]

I like that idea!

[tomtuna1978]

dude !!! from the pics that ive seen of you wheelin ... that aint overkill !!! let us know how that brace/girdle works out ! some of might be interested in one !

[willett]

my lord....

[special-K]

You could eliminate your frame and go unibody with that. That`s what I love about off road building...it`s about the beef! I envision a custom tunnel cover.

[wildwilly4x4]

thats the kind of brace I am talking about that my buddies built for their trannys

[johnnywagon]

Originally Posted by willett

my lord....

Haha, my lord indeed, wait until you see the finished product. I think I lost my mind and went way way overboard. I guess if you're gonna do something you might as well over do it.

More pix after paint.

[Shaffer4]

Overkill would be building some Boxed frame mounts and Tying it to the Frame.

[special-K]

I`m thinking you don`t want to break another case?Press 1 if your reply is yes.

[Thealien]

Originally Posted by johnnywagon

Haha, my lord indeed, wait until you see the finished product. I think I lost my mind and went way way overboard. I guess if you're gonna do something you might as well over do it.

More pix after paint.

Anything worth doing is worth overdoing!

Sticker on my helmet and words to live by