Shifting the 915 gearbox
01-14-2009, 09:11 AM
#31
Burning Brakes
Tons of good advice here. IMO, best steps are:
1. Replcace the cheap bushings and the coupler. For now, use stock everything. If you have a short shift kit, dump it. The longer throw slows the action inside the trans, taking it easier on old synchros and dogteeth.
2. Have your shift coupler and clutch adjusted by a 915 expert mechanic.
3. Drive, drive, drive. When shifting, be patient and shift slowly. I try to two-count, with a pause in neutral. The key point is gentle pressure as you are shifting into the next gear. You wll hurt nothing (assuming the clutch is disengaged) by shifting quickly out of a gear, but shifting into the next gear should be done gently. Now, you can force the shift into the next gear but that will just reduce the longevity of your gearbox.
As time goes on, it becomes a feel thing, and you will get quicker as you become more precise. Then you can focus on matching revs. Others have suggested heel-toe, but I would suggest thay heel-toe can seldom be accomplished on the street because you are seldom braking as hard on the street as you would on the track. So, to me, it is more rev-matching than actually blipping the throttle while under heavy braking.
One more recomendation to avoid the money shift: when up-shifting, rotate your hand counter-clockwise so that your palm is facing away from you. This will automatically put pressure to the right, towards upshifting. I learned this after yanking it into second instead of fourth, from redline in third: the result was about 9000 rpm, a broken rocker arm and six bent exhaust valves.
Ive been driving mine for six years both street and track (52 days) and have rebuilt the trans, replaced the clutch, installed the Seine Systems Robotech gate, and an 86 shifter (33% throw reduction). All good mods, but I would stick with the stock components until you learn the car.
Mi dos centavos.
1. Replcace the cheap bushings and the coupler. For now, use stock everything. If you have a short shift kit, dump it. The longer throw slows the action inside the trans, taking it easier on old synchros and dogteeth.
2. Have your shift coupler and clutch adjusted by a 915 expert mechanic.
3. Drive, drive, drive. When shifting, be patient and shift slowly. I try to two-count, with a pause in neutral. The key point is gentle pressure as you are shifting into the next gear. You wll hurt nothing (assuming the clutch is disengaged) by shifting quickly out of a gear, but shifting into the next gear should be done gently. Now, you can force the shift into the next gear but that will just reduce the longevity of your gearbox.
As time goes on, it becomes a feel thing, and you will get quicker as you become more precise. Then you can focus on matching revs. Others have suggested heel-toe, but I would suggest thay heel-toe can seldom be accomplished on the street because you are seldom braking as hard on the street as you would on the track. So, to me, it is more rev-matching than actually blipping the throttle while under heavy braking.
One more recomendation to avoid the money shift: when up-shifting, rotate your hand counter-clockwise so that your palm is facing away from you. This will automatically put pressure to the right, towards upshifting. I learned this after yanking it into second instead of fourth, from redline in third: the result was about 9000 rpm, a broken rocker arm and six bent exhaust valves.
Ive been driving mine for six years both street and track (52 days) and have rebuilt the trans, replaced the clutch, installed the Seine Systems Robotech gate, and an 86 shifter (33% throw reduction). All good mods, but I would stick with the stock components until you learn the car.
Mi dos centavos.
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silverlock (07-25-2023)
01-14-2009, 10:26 AM
#33
Burning Brakes
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2-3, 3-4, 4-5, 5-4, 4-3, in mine is just as smooth and quick as any Toyota/Honda out there.
1-2 and 3-2, is slowed but deliberate. 2-1 is done at a very slow speed...just to be safe, that shift for me is done at under 5mph, although I can get it nicely into 1st at 10mph.
I had alot harder shifting prior to replacing my clutch cable. Like others have said, let someone drive your car that is very familiar with the 915.
1-2 and 3-2, is slowed but deliberate. 2-1 is done at a very slow speed...just to be safe, that shift for me is done at under 5mph, although I can get it nicely into 1st at 10mph.
I had alot harder shifting prior to replacing my clutch cable. Like others have said, let someone drive your car that is very familiar with the 915.
01-14-2009, 10:29 AM
#34
Team Owner
My Trnasmision acts the same as Michaels with the shifts to second being the delicate one Figure I am due for a second gear synchro , but it is not ooo bad. I always fo into first as I am just rolling to a stop and this has worked very well for me.
01-14-2009, 10:47 AM
#35
Burning Brakes
Ed. The problem with clockwise rotating your palm toward you is that as you pull back, as from 3-4, you naturally pull toward you. With your plam rotated away, although awkward at first, you will never hit second by mistake. Also, as you push up from 2-3 it naturally pushes over toward 3, and from 4-5 toward 5. The chances of hitting 3 by mistake on the 4-5 are also greatly reduced.
I described my money shift to a club/pro racer with many years of experience racing various types of cars including 911s. He told me he had NEVER missed a shift and described this method. I have had surgery on my right shoulder resulting in arthritis and other painful stuff, so this rotation causes me some pain, but it is well worth the benefit. I spent the following winter rebuilding my engine, so the painful result of the missed shift is indelible.
I described my money shift to a club/pro racer with many years of experience racing various types of cars including 911s. He told me he had NEVER missed a shift and described this method. I have had surgery on my right shoulder resulting in arthritis and other painful stuff, so this rotation causes me some pain, but it is well worth the benefit. I spent the following winter rebuilding my engine, so the painful result of the missed shift is indelible.
01-14-2009, 11:19 AM
#36
Rennlist Member
Ed. The problem with clockwise rotating your palm toward you is that as you pull back, as from 3-4, you naturally pull toward you. With your plam rotated away, although awkward at first, you will never hit second by mistake. Also, as you push up from 2-3 it naturally pushes over toward 3, and from 4-5 toward 5. The chances of hitting 3 by mistake on the 4-5 are also greatly reduced.
I described my money shift to a club/pro racer with many years of experience racing various types of cars including 911s. He told me he had NEVER missed a shift and described this method. I have had surgery on my right shoulder resulting in arthritis and other painful stuff, so this rotation causes me some pain, but it is well worth the benefit. I spent the following winter rebuilding my engine, so the painful result of the missed shift is indelible.
I described my money shift to a club/pro racer with many years of experience racing various types of cars including 911s. He told me he had NEVER missed a shift and described this method. I have had surgery on my right shoulder resulting in arthritis and other painful stuff, so this rotation causes me some pain, but it is well worth the benefit. I spent the following winter rebuilding my engine, so the painful result of the missed shift is indelible.
01-14-2009, 12:39 PM
#37
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CW, CCW, secret palm rotating money shifts 
Great advice guys
I will take everything you mentioned into consideration. To be a little more specific, what i notice when N-1 or 1-2 shifting, there's a slight resistance before it pops into gear. I need to place more pressure on it that i would like before it goes in, keep in mind no grinding and im taking a great deal of care/time before engaging the next gear. Im under the impression this may be caused by worn bushings etc. Something i will look into. The first thing i'll do is use Swepco #201.
I just got my Bentley last night and was up into the morning reading it. How much i've learned! Now i only wish i had a place/tools to work on the car myself.
Great advice guys
I will take everything you mentioned into consideration. To be a little more specific, what i notice when N-1 or 1-2 shifting, there's a slight resistance before it pops into gear. I need to place more pressure on it that i would like before it goes in, keep in mind no grinding and im taking a great deal of care/time before engaging the next gear. Im under the impression this may be caused by worn bushings etc. Something i will look into. The first thing i'll do is use Swepco #201. I just got my Bentley last night and was up into the morning reading it. How much i've learned! Now i only wish i had a place/tools to work on the car myself.
01-14-2009, 03:21 PM
#38
I haddah Google dat
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nikkoa,
take your time, buy tools according to need. I noticed that a lot of pro quality tools are available now on Craigslist. I'd stay AWAY from cheap tools made in China as much as possible. Changing the gear oil is easy. Be sure to use jackstands to support the car.
Replacing the busings and checking the adjustment of the shift coupler will go a long way. For a better understanding of what they're talking about in terms of shift technique, "High Performance Driving" by Bob Bondurant is a good read.
take your time, buy tools according to need. I noticed that a lot of pro quality tools are available now on Craigslist. I'd stay AWAY from cheap tools made in China as much as possible. Changing the gear oil is easy. Be sure to use jackstands to support the car.
Replacing the busings and checking the adjustment of the shift coupler will go a long way. For a better understanding of what they're talking about in terms of shift technique, "High Performance Driving" by Bob Bondurant is a good read.
