What is the best tranny to buy for a 2.7-3.0L RS?

[82SC]

well I have not yet decided where to go with the engine, but at least I've narrowed it down to 0.3L in displacement.

What tranny should I mate with the engine?

I want a 915 (don't want expensice G50 conversions)

I was thinking a low R&P...I know some people say it is weaker, but the car will not be a racecar...

and I was hoping to lower the gearing in the future when it needs a rebuild (so a low R&P with maybe airport gears??)

or should I get a more modern 915 with electro speedo?

Are the casings different on the early vs late 915?

any other characteristics that makes one better then another?

Or if you really are an expert maybe a list of gears you would swap out of a early 915 and a late 915 (and cost if you knw)

hmmmmmmm...thanks

BTW what does a full set of "airport" gears or gears in that ratio cost?

[RoninLB]

82SC... not expert, but I got some good info from Dr. Timmins awhile back.. hit the site and search around.......Ron

www.instant-g.com

[CRH911S]

Check with Wayne for referals. I have heard nothing but good about Steve Weiner of Rennsport Systems-my recommendation.

I believe a properly rebuilt 915 is suitable for use with the 2.7RS engine in either the 210bhp or more potent 300bhp version. A possible area of concern might be in the clutch department with emphasis on the clutch spring.

The I-series Carrera 3-Europe/911S-USA cars introduced in 1975, were fitted with an 8.5:1 compression ratio version of the turbo engine, taken to 2,994cc by enlarging the bore to 95mm. New cylinder blocks where casted in aluminum. K-Jetronic fuel injection was standard. I can't put my fingers on it but I believe this engine produced something in the area of 200bhp. I believe a properly rebuilt 915 would suffice here also.

It really boils down to how much you want to spend and how you intend to use the car. Specialty 915 parts are hard to find and expensive.

Regards,

Clinton

[Bill Verburg]

Any of the 915s will be ok, The mg. case 915/49 from my '76 C3 was still going strong after 20yrs(5yrs infront of a 3.6). That said the al case 915(starting w/ '80 915/62) was stronger. The best/strongest stock box is the al/ case 915/67 w/ the external cooler. The 915/72 from '85-'86 uses different axles that may be incompatible w/ those used from at least '76 -' 84

If a 915/67 can't be had any of the others can be rebuilt w/ reinforced side plates and coolers and whatever gearing you want for a suitable fee. Warninig, gear sets are very expensive($6-800 per gearset) so think carefully about what you want.

There were numerous detail changes over the years, 915/60 U.S. and 915/61 RoW are 1977, the year when the "improved" asymetrical 1st 2nd slider was introduced, the output shafts switched in late 1985, somewhere in there the splines were changed to fine spline from coarse(all Carrera transmissions are fine-spline as was my '76 C3, not sure about US varients there may also be difference btween lsd and not) there was also a chnge ot 108mm cv joints.

There are least 4 style axle,
69-77 4-10 mm X 48 mm bolts and two pins per CV joint
78-83 6 - 8mm x 50 mm bolts per CV joint
84-86 6-10 mm x 50mm blots per CV Joint
there was some overlap of model yrs wrt to the 8-10mm bolts
87-89 6-10 mm x 50mm bolts per CV joint No bolts used on outside CV
joint.

[CamB]

You should think reasonably carefully about how short the gearing will be with airport gears - yes it gives much better acceleration.

But figure it out - if you have 120mph top speed at 7000rpm, then 70 on the freeway is going to be 4000rpm, and 85 on the interstate will be 5000rpm.

My BMW is only a 4spd and has a shorter diff, and a couple of hours at 4000+ RPM means mandatory earplugs.