Transmission rebuild/upgrade

[Mighty Quinn]

I searched for read threads and could not find anything.

Where does a guy start with transmission reconditioning and performance improvements, specifically for the 915 trans?

I know nothing about transmission repair/upgrading beyond adding a big clutch and throw out bearing.

If you were to have a 2.7 rebuilt with itb’s for a car designed for driving to the track.....what would you do to the transmission?

[chrismorse]

I just had California motorsports go through my 74 915. I haven’t the tools or knowledge to do the job, ( now, I’ve got the time to learn :-)
I am adding PMO itbs/EFI to a recently freshened 2.7 and it will see some track use, so, I opted for the Guard LSD, Wevo shift gate, reinforced side plate and teddy bear bearing support. Second gear had a weld repair to strengthen it.
Third or 4th gear and the r&p were also replaced, worn out. All of the above was in addition to the usual stuff, bearing bore repairs, bearings, sliders and synchros.
Had to Build a shipping box and screw it to a palate.
Recently, 915 parts are being manufactured with a gold alloy, so the prices are commensurately higher, an eye watering 13k.

If you are going to do significant tracking, depending on your HP, you might want to consider a spray bar/cooler set up to give the box a chance. Talk to the pros about when this is advisable and possibly changing your gearing.

Good luck,
chris

[Harpo]

Chris,

What is a teddy bear bearing support?

Thanks

David

[flat6pilot]

Originally Posted by chrismorse

I just had California motorsports go through my 74 915. I haven’t the tools or knowledge to do the job, ( now, I’ve got the time to learn :-)....
Recently, 915 parts are being manufactured with a gold alloy, so the prices are commensurately higher, an eye watering 13k....

Good luck,
chris

Wow! I just bought a rebuilt SBH 930 gearbox from Brian for my turbo'ed SC this past October for $9500 (included a $2000 core charge.) I guess I don't feel so bad now. Geez...

[Mighty Quinn]

Originally Posted by chrismorse

I just had California motorsports go through my 74 915. I haven’t the tools or knowledge to do the job, ( now, I’ve got the time to learn :-)
I am adding PMO itbs/EFI to a recently freshened 2.7 and it will see some track use, so, I opted for the Guard LSD, Wevo shift gate, reinforced side plate and teddy bear bearing support. Second gear had a weld repair to strengthen it.
Third or 4th gear and the r&p were also replaced, worn out. All of the above was in addition to the usual stuff, bearing bore repairs, bearings, sliders and synchros.
Had to Build a shipping box and screw it to a palate.
Recently, 915 parts are being manufactured with a gold alloy, so the prices are commensurately higher, an eye watering 13k.

If you are going to do significant tracking, depending on your HP, you might want to consider a spray bar/cooler set up to give the box a chance. Talk to the pros about when this is advisable and possibly changing your gearing.

Good luck,
chris

Great starting point thanks Chris.
I should correct myself, I won’t be using it at the track for racing as much as I’ll be getting driving lessons so I can learn to go fast. I want a fun motor for my outlaw that can drive there. I’ve got a trailer for when I brake it.

Yes, what is the teddy bear bearing support? Sounds technical, sounds German. 😀

[Trackrash]

There have been a couple of recent threads on 915s.

What 915 do you have? I see '69 in your garage.

So, I'm guessing you want to upgrade your trans for your 2,7? I would recomend a mag case 915. Better gearing and will fit with less fuss than a newer trans.

Scroll down in this thread and see some good info. Project Heavy Metal - an all steel classic, remastered

More good info. Gordo's 915 Transmission Rebuild

Teddy bear. https://www.pelicanparts.com/More_Info/CMS915BRT.htm?pn=CMS-915-BRT&msclkid=4214512d94d91fbaf18f0fab1eedfd56&utm_source=bing&utm_medium=cpc&utm_campaign=Shopping%20Ads%20-%20Porsche&utm_term=4581115198205407&utm_content=%24200%20-%20%24400

[chrismorse]

The teddy bear is a one piece bearing support, rather than the original two piece retainers. This helps retain the two bearings, (and shafts), maintaining a more precise location - keeping the shafts from spreading, misaligning the gears.
It probably helps prevent the bearings from loosening and spinning in their bores, as well.
chris

[mikedsilva]

Originally Posted by chrismorse

The teddy bear is a one piece bearing support, rather than the original two piece retainers. This helps retain the two bearings, (and shafts), maintaining a more precise location - keeping the shafts from spreading, misaligning the gears.
It probably helps prevent the bearings from loosening and spinning in their bores, as well.
chris

I've never heard to it being referred to as the Teddy Bear support, but I totally can see where it comes from! If they still call it that in years to come, I shall remember I saw it here first

[winders]

I like “snowman” more than “teddy bear”.

[patkeefe]

Peter Zimmerman has an excellent tutorial regarding the 915.
I sent mine to CMS a few years ago. It needed some special machine work, and I had them rebuild it plus add LSD. $6500. 915's are becoming rarer, and fewer parts are available.

[Trackrash]

Adding to the above, be careful buying a used transmission of unknown background. A junk trans will cost a fortune to refurbish.

[Matt Monson]

As referenced above, the definitive 915 document:

How-To: Porsche 915 Transmission Repair Tutorial Part 1 - Porsche Wiki

Even if you are going to send it to a specialist, it’s worth reading for information purposes and an understanding of improvement and upgrades that occurred to them over time.