Any way to improve shift into 2nd on 915?

[pete3799]

Originally Posted by 500_19B

OK, I know this seems really fundamental, but I just want to make sure I understand. I routinely do what I think is double-clutching for downshifts. Is this the correct sequence of events for double clutching:

1) Press clutch pedal, shift out of 1st gear into neutral.

2) Release clutch pedal.

3) Blip throttle.

4) Press clutch pedal and select second gear.

Let me know if there is something wrong with that.

I notice that in my DD (Subaru WRX), there is a LOT more driveline inertia and I never have to double clutch while upshifting as I usually need to wait for rpms to drop to the appropriate level as it is.

I noticed that in my short spell of driving the 911 before I tore things apart that it had much less inertia and the rpms would drop very quickly between shifts. Is that the crux of why we should double-clutch on upshifts?

Skip step 3 on up shifts....blip throttle on down shifts only.
Your trying to match engine RPM to trans. RPM.
When you let the clutch out after placing the trans in neutral (up shift= no blip)your allowing the trans. to slow down to match the engine RPM.
Likewise on a downshift you need to raise the RPM (blip) to match the lower gears RPM

[island911]

Originally Posted by don hopkins

I have a 1981 911SC which I have had for over 5 years. There is one thing that I really dislike about the car. That is shifting from 1st to 2nd gear on its 915 transmission. The transmission was rebuilt recently so I'm sure its performing as designed. ....

My 81 SC supposedly had a rebuilt 915 when I bought it. It had the same problem that you describe. One day it got stuck in gear . . took it to John Walker's workshop, and he did a rebuild. --it's awesome now.

The thing is, some will 'rebuild' with only new syncro's but re-use the sliders (which are likely worn) or re-use the worn dog-teeth.

A well sorted 915 is fast to shift.

[kodioneill]

Not to boast or say anyone is wrong but, all three of my cars shift into second up and down with no problems. I use kendall and all the linkages are tight and adjusted properly. The adjustments are the key and they are finicky.

[calling911]

Originally Posted by pete3799

Skip step 3 on up shifts....blip throttle on down shifts only.
Your trying to match engine RPM to trans. RPM.
When you let the clutch out after placing the trans in neutral (up shift= no blip)your allowing the trans. to slow down to match the engine RPM.
Likewise on a downshift you need to raise the RPM (blip) to match the lower gears RPM

Mine grinds 50% of the time upshifting if I dont blip.. so while Id normally agree with you I disagree

BUt mileage may vary.... I guess if you shift fast enough a blip is not needed but my 2.7 as previously stated spins down too quick.

[tcar]

Originally Posted by Steve@Rennsport

With all due respect, I'd kindly disagree,.....

Synthetic gear oils are not advisable with any 901-915-930 transmissions since those lubricants do not work properly with the Porsche baulk-ring syncros.

Non-synthetics such as Swepco #201, #210, Lubrication Engineers 703-704, and Kendall are the preferred products for these unique gearboxes.

Sorry if you thought I meant using a synthetic was OK, I did NOT mean or say that... that's totally the wrong thing for a 915.

Royal Purple, I've heard good things about.
Kendall, too.
Better than Swepco.

[jwakil]

Originally Posted by calling911

No.. not at all. In fact, you are wearing out your trans doing this.

Which one do you mean? Is it the pausing in neutral or the shifting at low RPMs that wears out the trans?

[Swoboda]

In reading about SW chips, I'm under the impression that the new mapping reduces the quick drop in engine revs.

Would this aid in shifting?

I don't have a SW chip in my car. Just based on what I've seem here.

[Joe Bob]

I run SWEPCO.....happy with it....

[kiwiokie]

I find all upshifts go a little easier if I do not lift completely off the gas while shifting such that the revs stay a little elevated. 1-2 has always been fine for me. 3-4 on the other hand can be a little difficult but my 915 is not the awful beast that some seem to be burdened with.

[calling911]

Originally Posted by kiwiokie

I find all upshifts go a little easier if I do not lift completely off the gas while shifting such that the revs stay a little elevated. 1-2 has always been fine for me. 3-4 on the other hand can be a little difficult but my 915 is not the awful beast that some seem to be burdened with.

You know, most modern cars do that automatically.

[Wil Ferch]

1.) regarding double-clutching upshift....all sequence shown is correct *except* don't blip throttle.....you are not rev matching going up...only down.

2.) What?....Swepco 201 , a non synthetic....has been the "de-facto" recommended lube "precisely" for the baulk-ring type synchromesh that the 915 box has. You're getting this goofed up with G50 trans, with it's Borg-Warner style (cone?) synchros....which DOES cater to synthetics. Make sure it's GL-5 rated.

Oops....didn't read all the subsequent responses...answers already noted.

[DanielDudley]

If you really have problems shifting, and it is not the box or the linkage, consider that your clutch or pilot bearing may be dragging.

[Va_Powerman]

Originally Posted by jwakil

Which one do you mean? Is it the pausing in neutral or the shifting at low RPMs that wears out the trans?

x2 - how is this wearing out the trans?

[kach22i]

Swepco, new shift ball bushing and coupler bushings...........and most importantly a Seine System shifter spring thing a ma jig.

PEL-SEINESHFT
Seine Systems Gate Shift Kit, 911 (1973-86)
Porsche 911 & Carrera Shift Linkage - Page 2


The best $150 you will ever spend.

[500_19B]

Thanks to everyone for the replies to my double-clutching upshift question. When my 911 is back together I will try that without a throttle blip on the upshift.

[Jack Olsen]

Originally Posted by island911

My 81 SC supposedly had a rebuilt 915 when I bought it. It had the same problem that you describe. One day it got stuck in gear . . took it to John Walker's workshop, and he did a rebuild. --it's awesome now.

The thing is, some will 'rebuild' with only new syncro's but re-use the sliders (which are likely worn) or re-use the worn dog-teeth.

A well sorted 915 is fast to shift.

I agree with all of this.

A good rebuilder like John Walker will know how to source replacement parts (and even to sometimes correct the currently-being-produced ones that are sometimes not to spec as they come off the shelf).

And a 915 shifts just fine when it's in spec.

Mine has been running Swepco forever and it shifts great. I don't need to 'think about' shifting at all -- much less double-declutch or count out numbers in my head or play with the throttle.

[calling911]

Originally Posted by Va_Powerman

x2 - how is this wearing out the trans?

If you are pausing in neutral with the clutch in you are wearing it out.. if the clutch is out then you are not.

[jdawg]

Can someone please give me concrete data on Swepco vs. Kendall. I have 2 Porsche mechanics & they are on opposite sides of the fence on this. My 915 seems to get harder to shift into 2nd as it gets hotter. I was told the thickness of Swepco would help w/ this but I have read on this site that it may shorten tranny life. My 911 is @ Eurowerks in Charlotte as we speak. If you guys can make a case for Kendall I am gonna have them change it while it is there.

[na2ub]

Originally Posted by Va_Powerman

x2 - how is this wearing out the trans?

Anytime you push the clutch pedal in, you are spinning the throwout bearing. This also goes for sitting at a red light with the pedal in. No big deal, until you have to replace the clutch only because the thowout bearing dies, which really sucks by the way.

Also, don't forget, if you upshift (of course) AND downshift, you are putting double the use on the clutch / trans. I usually let my brakes take the beating as I am slowing down, as they are much cheaper to replace. I only downshift when I am in speed-racer mode.

Doug

[Drisump]

915 shifting threads are always interesting to read, most guys experiment with technique and some want to improve it through component changes and adjustments. Some guys seem to be so comfortable with their 915, I think they must not notice the subtle things they do versus jumping into the wife's new Jetta. I've driven a number of examples of this tranny (a few having been recently rebuilt), and although there is definitely smoother action and faster shifts on some of these cars, I've never driven one yet that shifts close to modern standards. By that, I mean, Joe average jumping in a car and making it go smoothly with no instruction or experience. Guys with lots of experience with this tranny can shift pretty quick and smoothly.... but it requires time in the saddle. I personally find the fastest way between first and second is modifying engine speed and not allowing it drop off completely (as was said earlier), not a "blip"...... but a maybe you could call it "an extended quarter blip". Cheers