901 / 911 Transmission / Gearbox Oil Leaks

[strictly]

I have a sweet 1971 911 2,2 transmission (magnesium/die casting), which shifts like liquid silk, but its got an oil leak from the mainshaft / input shaft seal, a slight weep from the nose /shift rod seal, and a broken side cover piece for the clutch cable (pull type). Its the 2.2

SO

I'm going to do the following

1) INPUT SHAFT SEAL (Mainshaft Seal)

Looks easy enough (?), just carefully remove and fit a new one, like any other seal, which i have plenty of experience with, no problems there, as long as i don't scratch the input shaft or the seal bore.

2) SIDE COVER AND SIDE / HALF SHAFT (OUTPUT shaft)

This I need some big help with....

As I understand it the clutch cable outer sheathing moves in the pull type arrangement. The piece is broken off which holds the cable just under the side/half shaft. So I am going to remove the side cover, so i can either weld or have fabricated a repair piece. I understand the cable sheath needs to move, so it must not be an interference fit,

The side shafts, has an expanding bolt, does this need to be replaced with a new one? do the side shafts just pull out once the bolt is undone? I can see there is a seal to replace, along with a big o-ring for the side piece. Are they a PITA? and I should just leave the side cover on and fabricate around it? If not then i will pull the cover off to have it repaired.

Do I need to mark or lock the input shaft etc (in other words) does the replacement of the side shaft have to go into its exact place as before?

3) NOSE CONE SEAL

I should be okay here, I have done a couple on 915's. As long as i put the seal in the refrigerator, and gently press it in, with the nose cover off, it has worked every time.

4) PIVOT CLUTCH ARM

The 1970-1971 pivot arm/fork for the clutch, does it have bush which wears like the earlier design?

5) BOX Names

Am I right in saying, we say 901 for the pre 70 aluminium boxes, and 911 for the magnesium boxes (and then just 915 for either the mag or ally, 1972 to 1986 boxes)

[Trackrash]

The drive shaft flange comes out after the bolt in the center is removed. It can be reused. The seal and o-ring are a straight forward replacement. Hopefully your output flanges are not badly rusted. No special placement needed when replacement.

I had mine welded. Not that big of a deal, as long as the welder is familiar with magnesium. I would remove it to have that done.

Interesting about the release arm pivot bolt. The original from the factory in '70 had a cladding of brass. Those lasted probably as long as the clutch.

For what ever reason, all the replacements are steel and don't have the brass coating. I have found that those don't last very long. Maybe until it is time to adjust the clutch or about 2 years. I have a dozen broken ones from over the years. No mechanic I know of has ever come up with a long term solution except "put in a 915".

Which is a shame since those transmissions are such sweet shifting units. Good luck.

Technically you are correct on #5 except it think the '70-'71s are 901/911.

[Jon B]

Originally Posted by strictly

4) PIVOT CLUTCH ARM
The 1970-1971 pivot arm/fork for the clutch, does it have bush which wears like the earlier design?

5) BOX Names
Am I right in saying, we say 901 for the pre 70 aluminium boxes, and 911 for the magnesium boxes (and then just 915 for either the mag or ally, 1972 to 1986 boxes)

You are correct in saying Type 911 for the 70 & 71 911 transmissions. That type number should be stamped into the bottom of your transmission.
However, there were magnesium-cased transmissions in 69 that were still Type 901 and 902.

The original pivot bolt (5) on pull-clutch 911 transmissions had a nylon bushing (6), but these failed often and were replaced with the one piece steel design.
The 70-71 clutch fork itself never had a bushing.

[ed mayo]

It has generally been my experience that premature pivot breakage was largely caused by worn clutch discs and/or worn out pressure plates that required too much effort to disengage the clutch. If pushing the pedal down failed to have that 'over center' feeling then it was time to replace. You also can't use overly strong pressure plates.

[strictly]

Thanks for the replies, i have had a good read of all of them. Okay so that gives me plenty of comfort with regard doing the seals. The pivot i had no idea on, and i should expect to replace it regularly, so i will put it on the list to order. Engine getting plenty of work at the same time too =P