Yet another 915 rebuild thread...

[cashflyer]

Here is the chunk of metal that was found in the bottom of the main drive housing, after we removed the diff:


And here is a shot of the bearing end of the main drive housing. The arrow points to the race that is "loose".


You cannot move the race side-to-side, or up-and-down in the pocket. It can only be rotated in the pocket.

In some other 915 threads, I have read of people having great results with the proper loctite product, and I believe that this will be the path I choose.

$938+ for the Wevo fix, plus the cost of synchros and sliders to replace my bad items... well, that is not an option. I would just buy another trans before dumping that kind of money into this one.

[sjf911]

$938+ for the Wevo fix, plus the cost of synchros and sliders to replace my bad items... well, that is not an option. I would just buy another trans before dumping that kind of money into this one.

I thought the same thing when I did mine, but it appears to be a bigger problem in these older tranny's. A "new" one may have the same problem since it is not likely to be any younger than yours and may actually have higher mileage on the case.

[cashflyer]

Steve - the other problem would be that I think the Wevo fix would require me to get all the pre-load, backlash, and clearances reset. More time and money.




Just a curiosity here: I just did a quick Google to see about LS diffs... and the prices I see are over a grand JUST for the carrier.

Is that correct??!!!

[cashflyer]

Dan/Mike/Randy

I believe the trouble we were having in removing the gear clusters was due to a missed line of instruction. From another thread, John Walker says,

shift the mainshaft into 3rd gear, (that's up, toward the end of the shaft). be sure the pinion shaft is in neutral when you do that. leave the forks and shift shafts alone. wrap your hands around both shafts and forks with the trans bellhousing down on a table or the floor, and wiggle the whole works out.

I remember that Randy said the works just came right out after he "slid something up". My guess is he inadvertantly made the shift that I had neglected.

The gears will be removed from the shafts later today and I will post more findings then.

[OldTee]

Can a moderately mechanically challenged person with no knowledge about transmissions, but can overhaul engines (Porsche included) do a good (100kmile) overhaul?

[sjf911]

Can a moderately mechanically challenged person with no knowledge about transmissions, but can overhaul engines (Porsche included) do a good (100kmile) overhaul?

Yes, No, Maybe?
From the limited experience I have had with my rebuild, I would have to say it depends on what you define as an overhaul.
Replacing the 1st and 2nd gear synchro assembly is relatively easy. 3rd and 4th are a bigger challenge but doable with access to the right tools. Other problems such as bearing race re-setting, ring and pinion issues may be out of reach to do correctly.

[SP2]

OldTee,
I hope so because I did. JW told me "humans do it. It's in books."

[mmasse]

$938+ for the Wevo fix, plus the cost of synchros and sliders to replace my bad items... well, that is not an option. I would just buy another trans before dumping that kind of money into this one.

I had the same problem. I talked to PHII and they mentioned that in order to solve this you can have the outer side of the race plated, which will increase the OD of the race enough for it to be a tight fit.

Hope this helps

[Mahler9th]

Last year I had damage to my maincase bearings after a ring and pinion failure. I think I could have "saved" the maincase, but I needed new bearings. As I recalled, they were about $300 or more, even with the steep discounts I negotiated. They may be more now...

I decided instead to purchase a Wevo maincase. I already had the Wevo bearing retainer plate.

The Wevo maincase is extremely well designed and executed. It uses more readily available and less expensive bearings, so I will realize that savings down the road. I had to reset all of the shims anyway since I needed to replace the ring and pinion. Wevo recommend that I use Loctite and safety wire on the retainer plate bolts which I did.

I am using the 915 with a 3.8 liter engine in a racing application, so I am pushing it hard. However, even for a street car, if I had a marginal maincase I'd consider the Wevo unit. I also have a Wevo shifter and a Wevo coupler, and I recommend them as well... for street or track.

[cashflyer]

Started disassembly of 2nd gearset.
Posting for review and for reference:

[cashflyer]

How do I properly assess the condition of the synchro ring and brake band? They "look" good.

[dfink]

Others will probably tell you to replace them. If the syncro ring hasn't been flipped yet you may just be able to turn it over and reuse. That's what I did. I did replace the brake band although I don't think I needed to. If you look at the syncro ring one side will be a bit shiny and the other side a rough dull finish. The rough dull finish is what both sides of a new one look like. If you are willing to possibly have to tear down again in the future reuse and flip. If want maximum life and performance replace. A shop will likely always replace cause labor is more than the parts.
On the bearing perhaps a local machine shop could Knerl (spelling) where the bearing sits. This process basically uses a wheel with small points that make tiny impressions in the aluminum. For every little impression some metal is moved out to make the hole tighter.

[cashflyer]

I may flip the synchro rings. When I go back into it next time (eventually) I can change them. My labor is free to me, and the only recurring cost would be a few gaskets. Maybe by then I will have budgeted for things that I will be skimping on this time - like that Wevo fix. [edit: then again, the two are only about $170. I'll think on it.]

As for brake bands, I've been studying the workshop manual and they do not appear to be a wear item. They will be reused.

The synchro hubs will definitely be replaced. Here is a shot of the 1st gear dog teeth. All of them are nicked and worn, and can really be seen where the flash glare reflects off the rolled edges in this photo.



The slider is pretty effed-up also.

[cashflyer]

1st gearset, posted for review and reference:

[cashflyer]

Originally posted by Jim Sims
Transmission type (number on bottom); year and model of car?

Sorry I overlooked this, Jim.

Trans is 915/61
Car is 1978 911 SC, 3.0
Engine is not original. Not sure about the trans.

[Geary]

You'll find that the 1st / 2nd slider was a mismatch to the assymetrical teeth found on the 1st gear. That's why you see the odd wear on the 1st gear synchro teeth.

Correct matching parts:

1st / 2nd slider: 930 302 411 02
1st gear synchro teeth: 915 302 241 14

[cashflyer]

Is something I posted making you think my stuff is mismatched?

My slider has symmetrical on 1 side and asymmetrical on the other. And my 1st gear synchro hub (dog teeth) are asymmetrical. This should match up...

The slider # you posted is the same as the new one I'm ordering. But your synchro hub PN doesn't come up in the PP catalog.

The PN I have in my photo is from the PP catalog for a "915 Synchro Hub, Asymmetrical 1st, 911 (1977-86)"

Have I screwed up somehow?

[dentist90]

I have been thru exactly what you are going thru right now! I am not a mechanic, but like JW says there manuals for that. Sounds like you are on the right track. To get out the pinion shaft race you can tap it out from the diff side of the main case. To reinsert it place it in the deep freeze for an hour prior to pushing it back in. A bearing race adhesive will probably work just fine here.
Your reverse gear idler is a bit rounded, but if you haven't had any problem shifting into reverse it should still work. Like others have suggested there may be a problem with your clutch release. I have also nicked reverse downshifting from 5 -4. This will round off those teeth as well. As it is a gear only selected from standstill the worn teeth aren't as big an issue as shaft play.
Trust me when I say that changing your diff case, whether it be a WEVO modified case (excellent design for durability) or a new or used replacement case, involves a lot of careful measuring to reset the ring and pinion mesh. I'll be holding my breath when I drive my car for the first time after my rebuild. Keep your fingers crossed for me!
I'll be following your post intently. Lots of excellent help here. The toughest questions you can only answer for yourself, and they always involve the question "how far do I want to go with this?"
I guess we'll just have to write our own 915 rebuild book. Consider this thread another chapter!

[CarreraDan]

Harvey,
Looks like you got a lot done today. If you need any help next week my schedule is fairly open except for Tuesday. Today I spen five hours detailing the Carrera--looks damn good now. Have a great weekend.

[Geary]

Originally posted by cashflyer
Is something I posted making you think my stuff is mismatched? ....Have I screwed up somehow?

Not if the parts are both asymmetrical. The photo of the 1st gear teeth appeared consistent with a mismatch, but I could easily be wrong.