[Grady Clay]

Well I have a had a good look and talk with my mechanic and I am now pretty confident that the trans I have(that I bought and is apart on the bench), according to the numbers(901/13) (7193124) (901.301.301.0R) and to the clutch release bearing and the fork, as well as the 7:31 Crown wheel and pinion and the 190mm inside diameter of the diff support ring. Is the '69 trans that should fit my car. It is in pretty reasonable shape, with very little wear evident on any of the bearings , gears etc.
Good

It does have the Simplified differential that you speak of. The bolts that run thru the side flanges are worn at the little nubs at the end. Is the problem that the little nubs break off and then the shaft comes out?
Yes. It then destroys the transmission.

Is a rollpin drilled at another location enough to ensure it is not going to fail?
or should i try to find the parts to convert it to the 914 style diff?
Use the 914 parts. It is only a few parts inside the differential, not the differential itself. Do not try and drill and install a roll pin like the late 915 transmissions. Your differential steel casting won’t take that.

Where can I get those bits?
Post a WTB on Pelican classifieds

Do I need to buy the shift tool that pelican sells to set up the gears properly?
Try borrowing one

Should I get one of those Weltmesiter Lockout spring kits, that prevents from hitting reverse accidentaly?
You may only need some bushings and a lock-out plate. You may also need to repair your shift handle and shifter housing.


The rumbling in the trans in your 911 is most likely the 4-point ball bearing in the intermediate plate. If it is with road speed and not engine speed, it probably is the large pinion bearing.


What are your plans for refreshing the 901/13 on the bench?

At a minimum I would replace the two intermediate plate bearings and the necessary syncros, sliding sleeves and gear dogs. Of course new gaskets and seals. Careful inspection with a knowledgeable eye is essential. A “dam seal” in a modified clutch release (TO) bearing guide tube is worthwhile. Replace the two plastic bushings at the throttle bell-crank. A new ground strap is appropriate.

What is the condition of the speedometer drive? Install the better of the two in your 911, keep the other as spare. This is the time to replace the clutch cable and make sure you have the metal “plastic piece” where the cable connects to the clutch arm.

Since this is a magnesium casting you should carefully clean it and coat with Tectyl. PelicanParts is working a deal to supply that.

When you pull the engine, you should be prepared to replace the clutch and flywheel if necessary.

You are going to need at least 8 new M10 CV bolts and Schnorr washers. Carefully inspect your CVs and boots. You may want to clean, re-grease and replace the boots while you have the transmission out.

Another source of road speed “rumble” can be a rear wheel bearing. Make sure that isn’t your problem before you go working on the transmission.

Best,
Grady