Gearbox mount

[chrisg]

Hi, hopefully I can advise as I recently replaced the mount on my turbo when the gearbox was out in October last year. The bonded rubber metal mounts are designed in such a way that if they fail they still hold the gearbox in place no matter what the condition. However, as with all things involving rubber (and to a large extent metal as well...) there is always a level degradation/ breakdown. If I'm honest I can't say I noticed a huge difference with a new mount on and the one on my car was pretty shot - very wobbly with lots of give in it.. My advice (unless cost is a massive issue) whilst you've got the gearbox off, replace it. Unless a previous owner changed it with a clutch swoop a 24yr old car...... [no disrepect mines 22 yrs old ] Also to add to the list: Check the condition of the rubber fuel hoses in and around the tank and fuel filter Driveshafts inner and outer joints Gearlinkage on to of the gearbox Yours Chris

 

[barks944]

Cheers Chris, been looking at the linsay racing ultra mount, its not far off the cost of a new OEM mount and still has the rubber dampening. [link=http://www.lindseyracing.com/LR/Parts/944TRANSMOUNT.html]http://www.lindseyracing.com/LR/Parts/944TRANSMOUNT.html[/link] Does the torque tube have mounts as well? I checked the gear linkage at the shifter and transaxle ends and it wasn't in a great state at either end. Ive got a new ish shift lever so I'm going to fit that at the front and I think fit a nice new short shift kit at the rear. Anyone had any exp with either: [link=http://www.jmgshop.com/944924s-9xx-roadshift-quick-shift-133-p.asp]http://www.jmgshop.com/944924s-9xx-roadshift-quick-shift-133-p.asp[/link] [link=http://www.deutschnine.com/mm5/merchant.mvc?Screen=PROD&Store_Code=porsche-transaxle&Product_Code=D9-944II951S2-SSK-106-01-002&Category_Code=porsche-transaxle-944-turbo-s2-tuning-handling]http://www.deutschnine.com/mm5/merchant.mvc?Screen=PROD&Store_Code=porsche-transaxle&Product_Code=D9-944II951S2-SSK-106-01-002&Category_Code=porsche-transaxle-944-turbo-s2-tuning-handling[/link] I think I'm going to attempt a home TT rebuild. Should be interesting!

 

[TTM]

As Chris I would also replace it if there is no sign of it having been replaced before. Sure it's not a cheap part but it's one of these while-in-there things people often replace.

ORIGINAL: barks944 I think I'm going to attempt a home TT rebuild. Should be interesting!

Will be doing that next weekend if I'm not too lazy, as I received the "Super Bearings" from Constantine last week.

 

[zcacogp]

I've often pondered what the gearbox mounts on a 944 actually do. The forces on them will be pretty small. Small compared with what they could be; there is no (or minimal) longditudional torque, as the torque tube acts as a drive shaft and a brace to resist the torque. There will be a large amount of lateral torque, forcing the front of the 'box up and the back down, as a reaction against the torque applied to the driveshafts and on to the wheels. But this will be braced at a large distance by the torque tube, which will exert a lot of leverage (at about 5ft distance) holding the gearbox still. Yes, clearly it needs to support the gearbox while it is in the car, and hold it still enough for the gearshift mechanism to work, but I can't see the need for an especially strong gearbox mount. (Note: I'm not trying to express any authority on this matter, just the outcome of my thoughts! Please do correct me if/when I am wrong! [] ) Oli.

 

[barks944]

ORIGINAL: TTM Will be doing that next weekend if I'm not too lazy, as I received the "Super Bearings" from Constantine last week.

I was umming and arring about getting some of those a while back. What do you think? Got any pics? How much did it cost you to get a set?

 

[barks944]

ORIGINAL: zcacogp I've often pondered what the gearbox mounts on a 944 actually do. The forces on them will be pretty small. Small compared with what they could be; there is no (or minimal) longditudional torque, as the torque tube acts as a drive shaft and a brace to resist the torque. There will be a large amount of lateral torque, forcing the front of the 'box up and the back down, as a reaction against the torque applied to the driveshafts and on to the wheels. But this will be braced at a large distance by the torque tube, which will exert a lot of leverage (at about 5ft distance) holding the gearbox still. Yes, clearly it needs to support the gearbox while it is in the car, and hold it still enough for the gearshift mechanism to work, but I can't see the need for an especially strong gearbox mount. (Note: I'm not trying to express any authority on this matter, just the outcome of my thoughts! Please do correct me if/when I am wrong! [] ) Oli.

But there will be a big force on the mount during harsh cornering as the tranny/gearbox will want to move towards the outside of the car. The TT/Engine mounts will be fighting this force as well but I think its possibly still putting a decent load on the TT mount.

 

[barks944]

Dropped my gearbox last night as the beginning of a big chunk of work on my car. I was looking at the gearbox mount and I'm not sure how to gauge its condition, the rubber was showing no signs of de-bonding from the metal but it was rather soft and the gearbox could flap about quite a bit. Are they usually pretty stiff?

 

[zcacogp]

Yes, that is true. But such forces won't be that great, in the grand scheme of things. Compared to the forces on the brake calipers, or the engine/gearbox mounts of a front-engined, FWD car., for instance. And I wonder how much benefit there is to be gained from aftermarket gearbox mounts; are they solving a problem that isn't there?. Oli.

 

[barks944]

You may well be right, although I do get the sense when driving that the drivetrain is moving about a bit on my car. It certainly feels at time like mass is shifting about during heavy acceleration and then settles back after. I can easily move the transaxle about with my hands when it was in the car so I'm fairly sure it will shift a decent ammount under acceleration. Whats hard to know is wether my mount is soft due to original design or its age. The Lindsay mount looks a lot sturdier than the OEM one. Noise is a big consideration though as I don't want a load of diff whine coming into the cabin.

 

[TTM]

As far as I can remember about the new gearbox mount which I had replaced on the S2 during the clutch job, the rubber wasn't vastly stiffer or softer from the 100k miles old one that came off. Tom, the bearings cost a lot - $650. Will comment on them when they will be on the car. If the Lindsey gearbox mount is as stiff as the Lindsey half solid engine mounts I had on the turbo during the first 600 miles with the new engine then I wouldn't touch it with a barge pole.

 

[chrisg]

I can't remember why, but I remember talking to Andrew Sweetenham about engine and g'box mounts - he had a customer who'd fitted the LR full on race mounts and couldn't stand the harshness and vibration. Yes, you're all correct about torque forces etc, bear in the mind though that the rubber in the mount does more than just load bear/ mount the gearbox, it also dampens any vibrations or rumbles from diff bearings, input shafts, driveshafts etc. Even with brand new OPC engine mounts you still get a reasonable amount of engine movement, hence all the flexible pipes for the fluid systems and the intercooler, surely if you mount the gearbox too firmly you'll place twisting/ shearing force on the torque tube and engine ?

 

[barks944]

So as its all designed to move together it should probably be all OEM or all stiffened to keep things aligned.