Ive got a '99 2500 Silverado that I converted to four wheel drive several years ago with a NP241 from a '98 3/4 ton Chevy and a Dana 60 from a F350. The original 2wd 4L80E tailshaft and tailhousing were swapped out for 4wd ones by a transmission shop. The problem is that the 6 bolts holding the transmission tailhousing to the transfer case keep coming loose. Its happened quite a few times, even after cleaning and threadlocking the bolts.

Any ideas why this keeps happening?:confused:

Did you reinstall the truss rod that goes from the side of the tcase to engine mount? Without it, it may be moving to much and working the bolts loose.

I sure didn't. Didn't know of this truss, but that makes a lot of sense. Do you know what years have it? On the driver's side I'm guessing?

Thanks, this has been driving me crazy.

On the oldr passenger drop models, the rod is on the pas. side... Look on the side for (2) large bolt holes side by side.. Should be around 5/8-3/4" or so in diameter....
The factory case you took off should probably have one also and you may be able to resuse that one...

Check to make sure you are using the proper bolt thread, the metric bolts will be a touch bigger that the 3/8s ones.

Ive installed a passenger drop t-case and didn't use a brace for the front output side as the 88+ 241's didn't use one stock. Ive had no issue with bolts loosening, though I did have a problem with RTV seal holding. You may still need it, but with the light Al 241's i don't see why it would be required.

try using some studs instead of the bolts. and maybe even some ny-loc locking nuts. i have never had this kind of problem, but i have ran a few rigs without the brace. check for proper size bolts. i believe studs and lock nuts will fix it though.

I had wondered if they gave me the wrong bolts; which is the 241 supposed to have, metric or standard?

Metric I think. Typically everything that threads into an aluminum transfer case is metric.

Well, im going to try the studs and I can check the threads to make sure
when I take the transfer case out today. Thanks for all the help guys