t-case rod woes since 4bt swap

[BowtieBlazer]

I lengthened and rebent my t-case support rod to work with my 4bt 4l80e setup. Since then the rod has broken at a weld, I realized I never really welded it and had just tacked it, so I laid a good bead down. About a week after this I realize the bolt had walked out even with red locktite. So I get another grade 8 bolt loosen the two on the t-case, torque it to spec at the bellhousing then tighten the t-case mounting bolts back and all is good. Fast forward two weeks, I start hearing racket when I shut the motor down, after quick inspection of the brace rod its still tight but sheared the bolt right at the bellhousing. Where else should I look for support? Its quite obvious this rod play a role in distributing torque across the entire drivetrain.

A friend thinks because my R&P is a little large --3.42's-- for my 33" tires, I'm loading up my drivetrain

 

[Russell]

I think that those torque rods break more stuff than they save... I always remove them from all my rigs

 

[BowtieBlazer]

if it weren't redistributing torque what was it there for? I've seen plenty of broken 208's that didn't have one, none that did...granted the t-case has a 2ft lever on the bell-housing mount really they should move as a unit from the motor mounts to the crossmember. Thats before we consider the strain from 4x4

 

[Russell]

I, on the other hand, have busted two NP208s cause of having a torque rod, but never had a problem otherwise... Granted, both were on a truck which had a ton of frame flex, which a K5 doesn't have.

If you think about it, how much movement will that thin little rod actually prevent? And how much movement willl there be in the driveline before it fails regardless? The problem I have with the torque rod is that it puts all the strain on one side of the t-case and offers no support to try and prevent any torque in the first place.

 

[kennyw]

All I can say is I never got around to putting the torque rod on my K20... when the front axle was punched back 12" on the pass side during a front end collision, the driveshaft bottomed out and sent all of the impact into the tcase took and split it open. I thought I got lucky and the TH400 was ok until I removed the adapter and found the rear transmission housing missing a chunk.

I believe the purpose of the rod is more to save the transmission than the tcase. It is positioned at the point of leverage that would react at the transmission output bolt pattern. In my K20, it may not have changed much with the way the impact happened though. But it would have split the force between two points rather than putting it all on the back of the transmission mount.

If you design something different, talk to someone who does mechanical engineering about how to reduce the likelyhood of destroying the transmission case because you made the tcase housing too stiff.

 

[CrewCab59]

I think they do more Damage with them on , you have way to many things going on from frame flex,trans and engine. Now that you have the 4bt , what engine mounts did you use? The Th475 is the step van had the trans pan that added extra strenght to the case and engine adapter plate.

For those that don't know what they look like see pic.

 

[sweetk30]

and didnt the tourqe rod use a bolt stud up at the bellhousing ?

bolt-stud in tight . then rod on stud part and thighten nut.

mabye this will help keep it tight up at the tranny bellhousing.

 

[BowtieBlazer]

I've got a th475 in the driveway I'm well aware of the oilpan/integrated inspection cover. I used the factory motor mounting location, and the 93'+ motor mounts which are a little bit thicker than the older ones which looked identical to the 318,360,440 mounts. The 4l880e is also on a 700r4 crossmember with the factory 4l80e mount relocated about an inch and a half back. I removed the factory front crossmember and fabbed up my own.

I've never run a t-case brace rod on any of my past trucks, and some I really wheeled hard, but I also never ran a 4bt or big block in any of my blazers. Having seen the damage this motor has done in previous apps at low rpms I figured the rod was safe insurance that the entire engine and driveline would move as one unit. When installed I tightened the rod to the bell housing with a bolt not a bolt stud and then tightened the t-case side that way it should have been stress free at installed location.

I'm pretty sure its intent is to save the transmission in the case where the front drive shaft jams back into the front output, while I never see that scenario happening in my driveshaft's case I figured a brace is a brace.

 

[CrewCab59]

If your using the 1st gen dodge rubber isolators they are different than the 4b which looks like them but the rubber is softer on the 4bt Vs the dodge 6b due to the weight. I get calls like all the time about T-case and trans breaking all the time .

Just something to look at .

 

[BowtieBlazer]

hum....they are about a quarter inch taller too

you get that longer drain tube shipped out with MC's headgasket? What a cluster, I didn't think I needed to spot check people's work but that was a costly mistake on all our parts

 

[CrewCab59]

hum....they are about a quarter inch taller too

you get that longer drain tube shipped out with MC's headgasket? What a cluster, I didn't think I needed to spot check people's work but that was a costly mistake on all our parts

Already boxed up , ya it does add when it goes bad . It's a good thing you guys caught it before more damage is done. Use a light and look to make sure the rods are seated .

Call me if you have questions.