So what’s the thinking on 915 gearbox kits for a/6 build these days Options

[Steve]

I have a flipped r&p 915.. no side shift conversion bits though.
For a smaller displacement engine say 2.7 and under is a 915 even necessary?

IMHO, I don’t think a 2.7 or stock 3.0 needs a 915, but don’t go crazy off the line with first gear. The 2.7 came out in 74 and in 74 the 915 gearbox was 7:31 r&p same as a 914-4. Compare the gear charts, it’s not much of a difference. My first six was a 2.7 with webers and headers. I thought the trans felt right. As soon as I upgraded to the 3.2 the gearing felt all wrong and I felt like I was shifting all the time and that 1st was worthless. So I switched to a 3.2 1986 915 gear box. Expensive, but it matches the motor and the driving experience on the street and freeway is night and day better.

[Dr Evil]

I have a flipped r&p 915.. no side shift conversion bits though.
For a smaller displacement engine say 2.7 and under is a 915 even necessary?

No. The 901 is perfect for a 2.7, maybe unless you twin turbo it.

I second the Martin Bott kit over the Wevo. I have done the Wevo before, its tedious and it leaves somethings to be desired during set up. Still better than the external fixation methods, though. If going big power, a rebuilt 915, maybe LSD, and a Bott kit is perfect for most applications and worth the money. I do them at EvilWerks, BTW (IMG:style_emoticons/default/wink.gif)

[Tdskip]

Thanks for the discussion, this 915 will go with a 3.2L engine.

[Steve]

Thanks for the discussion, this 915 will go with a 3.2L engine.

I’m also running a later pedal set with clutch return spring and omega spring on the trans. More complicated, but more positive clutch response.

[mepstein]

Just saw this - https://m.facebook.com/RetroSportRacingGara...al&mt_nav=0

[speed metal army]

I have a flipped r&p 915.. no side shift conversion bits though.
For a smaller displacement engine say 2.7 and under is a 915 even necessary?

Is it Mag case 7:31 ??

Aluminum case, elec speedo

[old914dog]

I am with Dr. Evil.
I purchased his video and built a 901 behind a 3.2, 20.3 compression, Web 20/21 cam, headers, Chipped and never had a problem. It was not babied....but no Dairy Queen burnouts either. You can have 2 backups for the cost of a 915!!
But...I am a csob.

[old914dog]

Fat fingers....10.3 compression

[Justinp71]

I am with Dr. Evil.
I purchased his video and built a 901 behind a 3.2, 20.3 compression, Web 20/21 cam, headers, Chipped and never had a problem. It was not babied....but no Dairy Queen burnouts either. You can have 2 backups for the cost of a 915!!
But...I am a csob.

Yes I have a similar setup. You just use 1st as a parking lot crawler, on the highway you scream at about 3500 but that's typical 914. I was reading on the track cars that the 901's only last so long, but if you upgrade the cooling you can get them to last longer. Heck the early 350 SBC guys used them with 1st removed.

A later model 915 probably suits a 3.2 better for general street driving gearing though.

I think a common late 70's 911 mod is to go back to the early R&P for more acceleration. But I think 1st gear in the 915 can take a better beating.

I have a mid-engine 915 sitting on the shelf waiting for a future install... Haven't decided what direction I want to go with it yet.

[Steve]

I am with Dr. Evil.
I purchased his video and built a 901 behind a 3.2, 20.3 compression, Web 20/21 cam, headers, Chipped and never had a problem. It was not babied....but no Dairy Queen burnouts either. You can have 2 backups for the cost of a 915!!
But...I am a csob.

Yes I have a similar setup. You just use 1st as a parking lot crawler, on the highway you scream at about 3500 but that's typical 914. I was reading on the track cars that the 901's only last so long, but if you upgrade the cooling you can get them to last longer. Heck the early 350 SBC guys used them with 1st removed.

A later 915 probably suits a 3.2 better for general street driving gearing though.

I think a common late 70's 911 mod is to go back to the early R&P for more acceleration. But I think 1st gear in the 915 can take a better beating.

I have a mid-engine 915 sitting on the shelf waiting for a future install... Haven't decided what direction I want to go with it yet.

(IMG:style_emoticons/default/agree.gif) A 901/914 trans is quicker than a 8:31 915. A 901 is weaker than a 915, but the 901 is quicker on the track or autocross due to the 7:31 RP. It's also nice having 2nd and 3rd in the same plane. But for street, freeway and road trips, the 8:31 915 is nice. You have 5 usable gears, your not shifting as much and with stock gears you are cruising at 80mph at 3200 RPM's. If I was younger and still liked to hot rod around, I would of kept the 914 gear box and maybe put a taller 5th in it.

[slivel]

I never had significant problems with my 914 transmission in my 3.4l 290 rwhp (open exhaust) track car. Over 23 years of racing had only two failures and they were early on - one R&P and one gear-4 failure. Later, I did pull and freshen every 3 or 4 seasons and had no more failures. As I recall the pinion bearing and bearing race usually showed the most wear when we had the box apart for freshen. Because of this I would drain and replace the gear oil every season and look closely for gold flecks indicating a bearing cage was starting to deteriorate. Also had a magnet in the flow path to the oil cooler which can provide an early warning of problems.

Now the car is just a street hotrod and the gearing (AFNSY) is OK for the street. Hp is probably down 30-40 with mufflers. As has been said several times, take it easy when in first gear. 2-5 handled the rigors of racing very well. The gear box was well built with billet intermediate plate and trans cooler with oil squirters over the R&P and gears 3-4.

Lastly as my transmission tech said, you can rebuild a 914 box a bunch of times for the cost of a 915 conversion.

[rgalla9146]

I recently had my 915 / 916 set up by a very qualified retired shop owner.
He has the factory tools and experience to properly adjust drag and backlash.
Of course he can do the entire transaxle too.
He is in North Carolina and is open do this work at a reasonable cost.
I've known him for thirty five years.
If interested contact me via PM
Rory