Jacking points
 

1989 Porsche 944 2.7
Can you jack up the rear of the car on gearbox.When i try gearbox moves up a few inches.Thanks

You can. I do. PP also suggests it.
https://cdn4.pelicanparts.com/techarticles/Porsche_944_Turbo/01-BASICS-Safely_Jacking_Up_and_Supporting_Your_944/images_med/pic09.jpg

You can also refer to this "picture":
https://rennlist.com/forums/attachments/924-931-944-951-968-forum/1014523-lifting-points-porsche_944_jack_lift.jpg

These gearboxes are generally supported by (hung from) a somewhat flexible rubber mount, and there is just no way that I could see ever lifting the rear of the car with the gearbox, especially after I'd dropped my cars tranny awhile ago and thus got a good look.

While some folks replace these rubber mounts with solid mounts...I'm still not sure if the profile of this mount, or its associated attachment on the car and the tranny side - would allow for the mount's/attachment points survival were one to try to lift the car with the tranny.

I used to use the tranny as a jack point and I never had any problems (during or after).
Like you, I've dropped the trans a couple times and seen how it is supported. Now I use a side to side method to lift the rear which is a longer PITA. I wish I'd never looked.

Or this picture.


http://forums.pelicanparts.com/uploa...1740577782.png

Good use of Haynes books. Probably, the only good use. Chilton's, too.

On a late car, the trans mount is connected to the car with two very thin bolts. Although I have done it in the past, I try to avoid jacking the rear of the car this way to limit any potential damage to the bolts or the mount. I would imagine its the same/similar on an early car.

Furthermore it may also put pressure on the torque tube and front/rear bellhousings which is another reason I avoid doing it. The trans is connected all the way to the engine so any movement in the trans affects that entire drivetrain all the way to where the TT connects to the front bellhousing.

But I do agree it is super super convenient and tempting.

YMMV

early car - no problem. the trans mounts are big chunks of rubber on either side of the trans bolted to the car on a chassis rail with 2x 10mm bolts

late car - late mount is floppy but you can do it if you have no other option. the two bolts from the mount to the trans are torqued so really it's the clamping interface there carrying the load which is probably 2 sqin combined.

according to a chart i found on fastenal an M8 bolt at 16ftlbs has a clamp load of roughly 3500lbs so 2 of them would be 7k...