slingshot C2

Hello,
I recently purchased a converted car. It's actually quite the hybred of cars....

1977 911S with 1972 911E 2.4l motor (rebuilt with ~20000km on it), 40mm webbers, 915 tranny with replaced 1st and 2nd gears less than a month ago.

my problem is typical of all older 911 transmissions.
When shifting from first to second, it will only smoothly shift between 3000-4000rpm. any higher than that and it grinds terrible no matter how gently or aggressively it's actuated. I was hoping to bring this car to the track for a driver ed session... but am aprehensive because that's not the only problem with the tranny.
from 5th to 4th it's also finicky

It was serviced by a very skilled Porsche technician whom I trust very much... but I wonder if I'm going to be plagued with issues until I replace it?

(btw, the poopy 2.4 is coming out most likely this winter to be replaced with a 3.3L turbo motor)

here's a pic:
<img src="http://www.kompressorkanada.ca/dkl/DSCN1455.JPG" alt=" - " />

Steve Wilwerding

I'd say whoever did the rebuild either didn't do it correctly or didn't replace all that should have been replaced. It sounds like your second gear synchro is gone. I can't imagine someone would put in new first and second gears and not change the synchros, but I suppose it's possible. If possible, try to find out exactly what was changed in the transmission.

slingshot C2

1st and 2nd gear synchro's and dogteeth were replaced.
apparantly he's recommending a wevo coupler as my shifter box is old and worn out.
does this sound like a reasonable thing to replace?

Please excuse my ignorance.... I have been a VW tech for a dozen years, this whole 911 scene is new to me. The only reason I bought this car was due to the misfortune of a businessman who chose to save his business instead of keeping his toy.

Paul

Which oil are you using?

Lefty's Deceiver

Have you tried to double clutch on both the up and down shifts? I find this works perfectly for my 915.

Lefty

GeorgeMa

I would like to share that I cannot shift from 1st to 2nd until car has been driven for 5 miles or so, and then only below 2000rpm. Dr. Walker told me it is too early for a rebuilt. When car is cold, I go from 1st to 3rd.

I have driven other 915s without this problem.

George
1983 911 Targa

Bob D..

Before you bother with the WEVO or other couplers, just get the four plastic bushings in the stock linkage replaced and get the linkage adjusted. All of the plastic bushings were worn in my '84, and the difference after I replaced them was remarkable. Best $25 and hour that I have spent recently.
Bob
84 Carrera

Paul Conquest

Oil choice can also make a difference.

I recently purchased a '78 911 SC with 155,000 km and a tranny rebuild by the previous owner at 62,500 km (due to 3rd gear syncro problem). I recently changed from whatever unknown substance was put in my tranny way back then to Redline 75W90NS, which is a fully synthetic GL5 oil. (I understand the preferred oil is Swepco 201. However, I have been unable to find it locally in Edmonton, AB, Canada). Whereas before the change to Redline the tranny felt sloppy all around and the syncros were easy to beat in 1st and 2nd, I now find the engagement of the gears to be very crisp. I distinctly feel through the shifter the pause as the syncros speed/slow the gears, and then the gears engaging. It is quite a dramatic change.

The overall experience I recently had with my '78 911 SC is similar to the difference from changing to Redline in my '87 944 Turbo. It too was sloppy when I made the change and the performance increased significantly.

Synthetics also have much better high-heat performance (less breakdown). A friend of mine who is a mechanical engineer, ownes a Mack truck repair shop, and races 911s and 280Zs swear by Redline. He even sells it to his trucking customers.

On the downside, however, the syncros seem a bit stiffer. I've heard this is because the synthetic lubes are sliperier than conventional lubes and the loss of friction makes the syncros less efficient at regulating gear speeds. Of course. It may also be that the stiffness is because the syncros are simply working better now, and the ability to beat them has been largely removed.

I've heard it asserted that synthetic lubes may cause the syncros to wear faster, but I fail to understand how a sliperier oil might be the cause of this. I owned the 944 for three years after the change to synthetic with no noticable degradation in shifting, so have my personal doubts about the potential for synthetics to adversely affect syncro wear.

GrantG

944's use a totally different type of gearbox (from Audi) and synchros (Borg-Warner) than 915 box...