915 Transmission Shifting Improvements
 

When I got my '73 2 years ago, the transmission was very hard to shift without grinding and the clutch effort was very high. I had read all about the issues with the 915 and figured at worst case, I would need a rebuild.

Once I took possesion of the car, I had my shop install a new shift coupler and adjust it properly. It was like night and day! It shifted much more smoothly. However, It still occasionally wanted to grind in the 1-2 shift.

After about 1 1/2 years of suffering, I had the clutch and cable replaced. My pedal effort went from hard to "like butter". Should have done that a year earlier. :(

Last weekend, I changed the tranny fluid (the old stuff - Kendall had about 15,000 miles on it) to SWEPCO. Good news was that other than some filings on the drain plug the oil was dark but looked/smelled ok. :)

Now, all of my grinding is gone and it is one sweet unit! :cool:

I had read the threads on the "Holy Trinity" of the 915 Transmission: SWEPCO, New Coupler, Shifter Adjustment, with skepticism. In a way, I am glad I did them one at a time since I was able to see the incremental improvement with each step. Next time I would not wait so long.

If you are having problems, these may put off that rebuild.

There is one more bonus to add to the mix. If everything is good after you get coupler, cup, swepco, and adjustment done... Get the Seine Gate Shift Kit. Hands down the best $150 I've spent on the car. I love it. Before the install I was always a bit nervous when shifting, but with the Gate shift I ALWAYS know exactly where I'm shifting. It really brings the feel of the shift into the current decade.

http://www.seinesystems.com/GateShift-1.htm
and at Pelican at:
http://www.pelicanparts.com/catalog/shopcart/911M/POR_911M_pedals_pg1.htm#item1

I agree with the Swepco but went with a WEVO shifter which made an incredible improvement. SmileWavy

I wish I could get that kind of satisfaction about my shift coupler adjustments, they never seem to get all gears working well...

I'll second the Seine Kit. Got my mind back on driving and off of shifting!

Chris,

I needed to get all three done to finally get to this sweet spot. With 120,000 miles, I can;t undo the wear but I think, with care, I can delay the day.

i have done all of the items you've mentioned, except didn't use swepco -- just new tranny oil. the tranny oil contributed least to the improvements, but it did help.

someday, i'll change my tranny oil to swepco and see if i join the long list of converts.

I was skepical also. I am glad I did the changes one at a time to see how they helped. The SWEPCO helped but not as dramatic as the new coupler or new cable.

New cable and clevis...Swepco...bushings... New clutch and helper spring... all made a difference.

Taking it to a real pro for the adjustment though, was the capper. I had it adjusted "right",,,but this guy made it perfect. Saved my tranny some unnecessary wear. its still notchy, but Ive learned to coax it through some really tough LA traffic.

I went through the processes one at a time too. One thing I did that seemed to make a big difference, especially when shifting fast, was putting the sport engine and transmission mounts in. My car used to be harder to go from 1st to 2nd when the car warmed up. The sport mounts fixed that too.

I've done everything mentioned above, which helped, but here's where I am as of last night...

http://forums.pelicanparts.com/uploa...1076509453.jpg

The Wevo stuff looks like a great idea. But so much $$$ for all that? I saw the ad in the back of Excellence...$595 for the shifter, $895 for the internal kit and PSJ (precision shift joint- it's a u-joint for Pete's sake...) I dunno. I'd be interested to hear more feedback on the kit...I can't see how it would speed up a 1st to 2nd gear shift because of the inherent design of the 915 synchros, my biggest complaint.

-BG

A bit of an update.

I have been driving Smokey pretty regularly all spring and summer and the shifter/transmission feels better today than it did when i first completed all the "upgrades".

For the relatively low cost, if you are not happy with how your 915 is behaving, I would definately suggest you try these steps and wait few months before you rebuild.

I'm not so sure that the Seine kit would completely solve the 915 occasional missed shift problem. I'm sure it would work just fine under "normal" driving conditions. But, I think that under hard acceleration, sometimes the gears would not actually be in the correct positions for the gate... if the gate is on the shifter.

For example, I find that hard acceleration can actually move my 3rd gear position slightly to the right... enough to hit no-man's-land between 3rd and 5th. Could the torque of the engine be twisting the gearbox enough to do this? I think possibly yes.

I think Car and Driver or Road and Track suggested this in one of their 911 reviews from the '70s.

A quick search for WEVO will give you many opinions. But the my thought is a full monty WEVO 915 setup beats a early G50 hands down.

In that situation it makes the WEVO stuff look inexpensive.

Just so there is no confusion - none of the WEVO products are designed with the intent of speeding up the the shift speed of the 915.

The products completely change the precision and feel of the 915 - that translates into more gear selection confidence - but not necessarily speed.

As BGCarrera32 rightly states - 915 shift speed is a function of the Porsche synchronizer architecture.

Regards

Hayden

When you swap the fluid in the 915, be sure to drop the shift plate at the bottom and check the condition of the four studs that hold the fork. When they loosen, and they do, you get sloppy shifting.

Pull the studs and clean with Chemtool or Gumout. Dry, Loctite the studs in and carefully thread on the nuts.

John

There are only three M6 studs holding the guide fork in place!

Either studs or nuts can work loose ... so I vote for Red Loctite on the end of the stud going into the cover plate, and Blue Loctite on the end with the nut on it!

Another incremental improvement in shifting feel and control can be had by replacing the OEM elongated-hole shift coupler bushings with either the 914 parts, or the Weltmeister bushings! A bit more noise will be introduced into the cockpit via the shift rod and shifter, but the improvement is worth it!