Transmission Casing & Exhaust
 

Hi All,

I am hoping someone can explain something to me. My car is currently getting an IMS/RMS upgrade done (along with a few other things) and my mechanic has advised that the previous owner had over tightened the exhaust onto the transmission which has caused 4 cracks and the bolts wont tighten?

What they are saying is that they can oversize the mounting holes, and then retap it and this will remove the slight cracking around the hole and with larger bolts the screw will tighten and allow the exhaust to be mounted properly.

He reckons if this doesnt work then i would need a new transmission casing.

My question is, 1) how important is it to mount the exhaust to these points? and 2) where does the exhaust mount to the transmission? Ive looked in my 101 projects book to look at the transmission and cant figure out what he's talking about?!?!? and 3) really? A new transmission case???!?!?!?!?

Thanks in advance for ur help!

not sure how these would crack from overtightening unless someone tried to feed a larger bolt into the holes OR the entire muffler simply hit the ground at some point. at any rate, the photo below shows the back of the car with the bumper & exhaust removed. note the three bolt holes on the back of the transmission. a bracket bolts here; this actually holds brackets #5 and #8 in the diagram below that. it provides the main support for the muffler & is 100% necessary.

without seeing the cracks, i can't say whether their proposed repair would work. i CAN say that swapping out transmission cases is a ridiculous proposition. before you do that, you can have a welder repair the case by either filling the holes & re-tapping OR by cutting off some of the threaded bosses & welding on some aluminum nuts. MUCH cheaper & easiser than swapping out the case.



http://i156.photobucket.com/albums/t...1/_MG_7648.jpg


http://i156.photobucket.com/albums/t.../Exhaust-1.jpg

Maybe they meant just finding a used rear case half but I would try replacing the bolts with studs & nuts.

Thanks for the picture, now at least i can visualise it while talking to the mechanic and also ask the right questions!

If his plan a doesnt work ill see if it can get welded up. I think this damage was caused by the previous owner when he got rear ended. Had a porsche pre purchase inspection done, but they didnt pick up on this... Annoying but it happens.

Cheers for the info

You can also buy a performance muffler. The original Porsche muffler is large and heavy. Most after market mufflers do not even use those mounting points,

Look at the pictures in the Stebro exhaust thread, They only mount with the top bolts and to the pipes.

the top bolts still mount to the transmission. the stebro mounts to part #11 in the diagram above, which mounts to the transmission bracket #5. most aftermarket exhausts work that way.

Another possibility for a repair might be to use Timeserts. There have been other posts on the forum about using these and they look to be good alternative for repairing stripped out threads.
http://www.timesert.com/

timeserts are good stuff

.....the muffler is not that heavy. could you not just weld the bracket to the case. you can disconnect it from the muffler from the top.

Thanks for the help guys. They ended up using metal putty to cover the cracks and timeserts. Working a treat!