Gearbox mount and flex disc

[georgem]

I hope you all had a joyful Christmas - ours was the usual - hot and humid: perhaps somewhat different to many members of this group (not counting the other Aussies)

However life in the Pagoda garage continues on through the festive season; I am getting the engine ready to go back in after a major smash repair. I expect the body back in a couple of weeks. I am replacing all engine and transmission mounts as well as the flex disc and I have a couple of questions re the last two:

Transmission mount. I have a later model 230 so the transmission mount has a single bolt screwing up from below. Looking at the SLS website it gives directions that the transmission mount should be adjusted to provide a staight line from engine through the prop shaft to the diff. ie minimul  twist on the flex disc when at rest.  How is this achieved?  The mount kit came with two large rubber washers, one about 2mm thick, the other about 7mm. Once I solve the problem of alignment, if the gearbox needs to be raised, then these washers could sit on the bolt between the support plate and the mount but I cannot see them doing it for too long before they compressed.

Flex disc. The replacement flex disc provided by the Classic Centre (part # A 108 410 01 15) is not like the old one - its basically a flat ring of rubber with the six metal sleeved holes in it. Its as thick as the widest part of the old one but it seems like it will be much stiffer than the old. Is this the new replacement part or have I been sent the wrong part?

Any help and or suggestions would be greatly appreciated.

Cheers

[George Des]

George,

I'm glad you asked this question regarding the alignment. I've seen that same diagram on the SLS site and am wondering the same thing. How do you measure the offset from a straight-line alignment? The adjustment once you figure this out is pretty straight-forward. I've also seen where the round flex disk is sometimes provided in place of the old flex disk. Can't help here as far as whether it is a good replacement but I know the old style one is readily available through a number of third party suppliers. Hopefully someone on the Forum will know the answer to both these questions.

George Des

[ja17]

Hello George,

The round flex disc is the correct replacement. It is better, in that it is constructed so it can be mounted in anyway position. It does not need to be indexed to one position like the old disc. In addition it is more robust and should last much longer than the original. the bolt hardware is the same.

The old hex shaped flex discs, which are available, are most likely "new old stock" and are less desirable than the new improved versions. In addition the old style must be installed in a certain orientation or they will not last.

[georgem]

Thanks George and Joe,

George re the alignment of the drive train, I guess my best bet is to rotate the flex joint with the rear wheels jacked up and the weight on the axle so it is sitting normally. If, when the prop shaft is rotated, the flex disk doesnt flex too much its probably close enough for Government work, if it needs to go up, the mount can be packed with metal spacing washers. Thats about as accurate as I can figure unless there are other suggestions out there.

Joe, thanks for reassuring me that I had the right flex disk.  I have noticed though that the shouldered short bolts that face forward are too long.  If I use them with only the supplied washer against the bolt head, then the shoulder will protrude forward of the transmission flange and stop the flex joint being tightened against the flange. They are also a touch too long and hit the transmission case. If I use two washers per bolt then its ok. The bolt shoulder will then not protrude outside the hole in the flange and I can get the bolt torqued to specs.

Thanks again to you both.

Cheers

[ja17]

Hello George,

Do you have the centering flange on the driveshaft end? Without it the bolts will surely be too long. The centering flange is critical, check to make sure no one has left it off.

[georgem]

Joe,

I have the flange, however from what I understand this is held on by the three long bolts that have their heads on the transmission side of the disk. The shorter three, which have their nuts on the tranny side are the ones that are a touch too long. (I`ve followed the diagram in the Tech manual, even though it shows the "old" style disk.)

Packing these three out with an extra washer under the head will bring the shoulder back below the tranny flange hole (so I can tighten it) and stop it hitting the transmission itself. I just have this nagging feeling that the location of the  bolt shoulders  has something to do with limiting the compression on the flex disk and that my solution may have solved the length problem but will interfere with the tension on the disk ie allow me to squeeze the disk too much.

George

[ja17]

Interesting....... All the bolt heads are on the drive shaft side of the disc (toward the rear).   I have installed some of these new flex discs already and have not experienced the issues you are having.  Not sure what to tell you.  Check the disc thickness. It should be the same.   

Yes, definitely add a washer to keep the bolts from hitting the trans housing for now.  Keep us up to date.

Joe