915 rebuild and ITB/EFI project, here we go!

[evan9eleven]

Looks like my winter projects are lined up for me! 1st time engine drop, done solo. Its amazing what a 2-post lift and some planning can do. The lump is out, and of course the engine bay selfie had to happen! I'll be doing a rather complete rebuild, with new 2nd, 3rd, and 4th gears from Matt at Guard for lower ratios. Plus I'm dumping CIS and adding a full ITB/EFI kit from Al at X-Faktory. If you're more interested in the EFI/ITB project, that starts out on page 11. The first pages chronicle my 915 rebuild and diff setup epic.






I was debating if we really needed another rookie 915 build thread, but in spite of all the great info here and elsewhere (Peter Z's tutorial for example, Gordo's thread, and the factory manuals) I have struggled to find a comprehensive list of all the current parts required in one place. So I've compiled what I think is a nearly complete list, and will edit it as needed so others can benefit from it in the future.

I'd love any input I can get on this, so I get it right-- and to start off I have 3 questions:

When is it necessary to replace engergizer/anchor and stop blocks?
What about replacing the brake bands?
Can anyone help with info on a ZF LSD rebuild, parts and details?

These are a couple items not covered in the tutorial, but it seems replacing them may be wise. The gearbox has 164K miles on it...

915 (insane) rebuild parts list

Main shaft bearing (at diff housing): 999 052 030 00
Main shaft bearing (at clamping plate): 999 110 032 00
Main shaft bearing (at center housing): 999 110 025 00
Pinion shaft bearing (at pinion head): 999 110 146 01
Pinion shaft bearing (at clamping plate): 999 052 043 00
Pinion shaft bearing (at center housing): 915 302 399 06
1st gear synchro ring: 915 302 301 06
1/2 sliding sleeve: 930 302 411 03 (P original) or 930 302 411 02 (aftermarket)
2nd gear synchro ring: 915 302 301 04
3rd – 5th gear synchros: 911 302 301 06
3/4 sliding sleeve: 911 302 411 20
Pinion shaft lock nut: 915 302 282 00
Main shaft lock nut: 999 034 033 00
Diff carrier bearings (2): 999 059 027 02
Needle bearings (5): 999 201 470 00
Needle bearings, reverse (2) 999 201 107 00
Gasket set: 915 300 911 01
1st gear dog teeth, R&S: 10-1550-312-M157
2nd gear dog teeth, R&S: 10-1550-318-M157
3rd-5th gear dog teeth, R&S: 10-1550-315-M157
Brake Bands (3): 911 302 316 08
2nd gear double brake band: 928 302 318 01
1st gear anchor block: 928 302 321 00
2nd gear anchor block: 928 302 322 00
3rd-5th anchor 911 302 317 01
1st-2nd stop block: 915 302 315 01
3rd-5th stop block: 930 302 325 11
Castle nut 900 079 009 00 (or can be reused)
LSD discs for ZF factory unit? (4pcs?) 917 332 552 12 OEM
Pinion shims:
0.10 mm – 915.302.268.03
0.15 mm – 915.302.268.04
0.20 mm – 915.302.268.05
(I've omitted the 5th gear sliding sleeve, I hope I don't need one as its $$$!)

Obviously an over the top list, but good to not miss anything. More soon!

[Peter Zimmermann]

We're here for you! When you post pictures please make sure the parts are clean and dry!

BTW; brake bands, anchor blocks, etc., are usually OK to re-use. So are 3-5 dog teeth, but we will see. Good choice on the bearings! 160K miles is between a rock and a hard place. Some 915s won't look like they need bearings at that point, but replacement is not a bad thing.

Don't forget to plan to repair a loose pinion bearing race, check local machine shops for someone who is familiar with that repair!

[WP0ZZZ]

Both the gearbox and ITB/EFI projects look really interesting! Thanks for sharing them with us.

Have you had any thoughts about which ratios to pick for 2nd, 3rd and 4th?

[pampadori]

That is your garage with multiple large tool chests, plumbing with sink, and a 2 post lift and this is your first engine drop? I don't feel sorry for you one bit. Not a single bit!

[evan9eleven]

Originally Posted by Peter Zimmermann

We're here for you! When you post pictures please make sure the parts are clean and dry!

BTW; brake bands, anchor blocks, etc., are usually OK to re-use. So are 3-5 dog teeth, but we will see. Good choice on the bearings! 160K miles is between a rock and a hard place. Some 915s won't look like they need bearings at that point, but replacement is not a bad thing.

Don't forget to plan to repair a loose pinion bearing race, check local machine shops for someone who is familiar with that repair!

Thanks Peter! Much appreciated! I promise to follow your sage advice on clean and dry parts. You left us plenty of reminders of this in the tutorial!

Yeah, I'm thinking I'll just do all the bearings. I don't want to do this job again anyime soon. I'm thinking of sending the diff case down to TwinSpark in Holland for the bearing race repair. These guys are hardcore on this stuff, and there are no local options for me.

One thing I know I'll need help with is setting up the diff. The backlash and preload setup does my head in but I'll reach out when I get that far. I also haven't found any info on how to rebuild the ZF factory LSD (mine is a /63 box from 1981.)

[evan9eleven]

Originally Posted by WP0ZZZ

Both the gearbox and ITB/EFI projects look really interesting! Thanks for sharing them with us.

Have you had any thoughts about which ratios to pick for 2nd, 3rd and 4th?

Thanks! I took Matt's advice on what a good setup would be, and went with a 2.056 2nd, 1.55 3rd and 1.174 4th. I'm also putting in the Guard 1-piece bearing retainer.

[3rd_gear_Ted]

Your buggy bumper car has the omega spring clutch arm set up?
Are you keeping that type clutch arm set up going forward?

[evan9eleven]

Originally Posted by pampadori

That is your garage with multiple large tool chests, plumbing with sink, and a 2 post lift and this is your first engine drop? I don't feel sorry for you one bit. Not a single bit!

You shouldn't. I'll try not to mention that I also have a beer fridge, heat, and second floor mancave with toilet. Oh and hot water in the sink! This is my first proper garage, and I went all out. Can't have kids so I'm having all the fun I can on this go round.

[evan9eleven]

Originally Posted by 3rd_gear_Ted

Your buggy bumper car has the omega spring clutch arm set up?
Are you keeping that type clutch arm set up going forward?

I didn't know there were options-- please enlighten me. I had just planned on putting the omega spring OEM version back on.

[WP0ZZZ]

Originally Posted by evan9eleven

Thanks! I took Matt's advice on what a good setup would be, and went with a 2.056 2nd, 1.55 3rd and 1.174 4th. I'm also putting in the Guard 1-piece bearing retainer.

I've been toying with the idea of shorter 2nd, 3rd and 4th gears on an SC myself.

Here is a plot comparing my latest virtual iteration with your ratios. In my case 4th is quite long because I would like it to be the top gear when I'm driving at a track with 5th being used exclusively for driving to and from the track/mountains.

Since I drive mostly on mountain roads, I'm particularly interested by the exit from low-speed corners. The blue line at 50 kph is there to show the rpm for such corners.

[evan9eleven]

Originally Posted by WP0ZZZ

I've been toying with the idea of shorter 2nd, 3rd and 4th gears on an SC myself.

Here is a plot comparing my latest virtual iteration with your ratios. In my case 4th is quite long because I would like it to be the top gear when I'm driving at a track with 5th being used exclusively for driving to and from the track/mountains.

Since I drive mostly on mountain roads, I'm particularly interested by the exit from low-speed corners. The blue line at 50 kph is there to show the rpm for such corners.

Thanks for the charts! Its cool to visualize it like that. Where I live we have endless twisties, mountains, and low-speed driving in general, so I'm hoping that these ratios will make the car a bit perkier and fun to drive. The ITB setup probably won't hurt either.

[evan9eleven]

Check this out: intact paint mark on one of the nuts. Not sure, but could it be the box has never been opened up?



I separated the gearbox from the engine, and man, I've got cleaning to do. Engine stand arrives this week so I can start the teardown!



In the meantime I pulled the pressure plate and clutch disc. I'm no expert but it looks like these parts are still serviceable. Or? I have no idea how many miles are on this clutch, my P-shop thought that some of my shifting difficulties could be down to a weakening PP that wasn't allowing full disengagement. Biggest symptom they said was grinding when shifting into reverse. Other then that, take up was smooth (though somewhat abrupt.) All feedback appreciated!

[Peter Zimmermann]

"Grinding" while engaging "R" can usually be corrected by selecting either 2nd, or 3rd, gear BEFORE shifting into reverse. The reason for my mentioning two different forward gear selections is that some transmissions "like" being shifted into 2nd better than 3rd, some transmissions are opposite.

Judging by your paint mark I would guess that your transmission is a virgin. Too bad that you can't find a record of clutch replacement, yours definitely doesn't have 160K + miles on it; at least I don't think it does!

[evan9eleven]

Originally Posted by Peter Zimmermann

"Grinding" while engaging "R" can usually be corrected by selecting either 2nd, or 3rd, gear BEFORE shifting into reverse. The reason for my mentioning two different forward gear selections is that some transmissions "like" being shifted into 2nd better than 3rd, some transmissions are opposite.

Judging by your paint mark I would guess that your transmission is a virgin. Too bad that you can't find a record of clutch replacement, yours definitely doesn't have 160K + miles on it; at least I don't think it does!

Thanks Peter!
Just to be sure I went digging in old receipts, but I don't have any going back more then 8 years or so, and maybe 22K miles. Nothing indicating a clutch replacement in that time. (I've had the car 3 years.) I agree, someone must have replaced that clutch at some point in the not so distant past. Given that this rebuild is already shaping up to cost a fortune, I'm seriously considering just reinstalling this clutch.

[Peter Zimmermann]

Don't touch the disc unless you're wearing latex gloves, believe it or not a little finger oil can actually cause light chatter. Wrap those parts in clean cloth/plastic and put them away until you decide!

It's funny, I was going to offer an opinion that your clutch looked more like a 30 or 40K mile unit.

[Clay.0]

Looks like a fun project

[evan9eleven]

Originally Posted by Peter Zimmermann

Don't touch the disc unless you're wearing latex gloves, believe it or not a little finger oil can actually cause light chatter. Wrap those parts in clean cloth/plastic and put them away until you decide!

Gloves only, and I'll stash them safely away.

Peter, about my LSD question. I am struggling to find good information on doing a DIY refresh of the factory ZF unit, or a comprehensive parts list. Can you offer any of your usual wisdom here?

[Peter Zimmermann]

Originally Posted by evan9eleven

Gloves only, and I'll stash them safely away.

Peter, about my LSD question. I am struggling to find good information on doing a DIY refresh of the factory ZF unit, or a comprehensive parts list. Can you offer any of your usual wisdom here?

Yep. Your factory manual (if it covers Carrera) should have a section on how to test the LSD once it's on the bench. I'll bet it checks out just fine. The info for a 40% set-up is in the 911 Carrera manual, Section 39, pages 39-13 to 39-19. My factory manual for "Model on '72" does not have this LSD discussion.

[evan9eleven]

Thanks Peter! I'll check my manuals.

The engine stand and benchtop press arrived today; I'll have a go at degreasing the beast tomorrow evening so I can hopefully start the teardown this weekend. I've decided to open it up before ordering parts, even though I plan to replace most of the major bits.

Speaking of parts I've been advised that when it comes to synchros that the original Porsche items are the only way to go, but that with bearings the equivalent FAG and Timken units are just fine. The head scratching really starts when there are two different aftermarket bearings to pick from our host. Like the mainshaft bearing 999.052.030.00. Besides the $224 P original version, there are two from FAG. One at $116 and one at $58. I'm more then happy to settle for one of the less expensive two given the manufacturer, but what makes the difference between those?

It gets even more confusing when the manufacturer is just "OE Supplier" or "OEM" or "IR Torrington" or something else. If anyone can enlighten me here, I'm happy for any tips I can get.

[kevingross]

Originally Posted by evan9eleven

One thing I know I'll need help with is setting up the diff. The backlash and preload setup does my head in but I'll reach out when I get that far. I also haven't found any info on how to rebuild the ZF factory LSD (mine is a /63 box from 1981.)

On the LSD rebuild, what I would generally recommend is:

• A complete tear-down, cleaning, and inspection. Any galled, damaged, or obviously heavily worn parts should be replaced.
• Per the workshop manual, measure the assembled clutch pack and case, and adjust the "outer plates" used to bring it to the recommended difference.
• Often a good idea to replace the Belleville (cup) washer springs because they fatigue over the years. New ones measure about 3.6 mm in height if you lie the spring on a straight-edge and use a depth gauge to measure height at the center.
• Check the break-away torque, make sure it is in range per the manual. It is not as critical as some would believe for a street car, but it should be in spec.

On the ring-to-pinion backlash, again follow what the manual says to get it within the specified range. You need not buy the factory tools. For years I used a simple home-made equivalent, picture below, that in fact works better than the factory tool when re-using differential carrier bearings. (And then I bought the factory tool, because of course he who dies with the most factory tools wins.) There are lines drawn on the angle iron stock at the nominal radius at which to measure free-play.



Best of luck with the project, and keep smiling! Pete's wiki on 915 rebuild is fantastic and will see you through the project.