The 993 re-gear challenge - The Street version
11-02-2009, 09:31 AM
#31
Bill ,your last example where you keep 1 and 2 and move 6th to 5th is great only wondering if i have 275- 40 -17's in rear versus your example of 265 35 18's if 6th will drop even more ,,cause if so think i need to make it slightly taller for track such as VIR ? would you aggree ? Thanks for all the information very enlightening ...everyone knows i need that 
here's the #s w/ 275/40x17 instead of 265/35x18
Set # Ratio Max RPM @ Max RPM Next Gear RPM Drop
1st 11 : 42 3.818 6800 38.0 3647 3153
2nd 21 : 43 2.048 6800 70.8 5181 1619
3rd 27 : 38 1.560 6800 93.0 5409 1391
4th 34 : 38 1.241 6800 116.9 5699 1101
5th 25 : 26 1.040 6800 139.5 6022 778
6th 38 : 35 0.921 6800 157.5
11-02-2009, 02:28 PM
#32
Rennlist Member
Cheapest most effective way retains original R&P
-- New 3rd gear at about 1.65
-- existing 3rd becomes 4th
-- New 5th gear at about 1.117
-- existing 5th becomes 6th
Gives best spread and makes the ratios closer and more usable. Not to tall a 6th for cruising and you are never going to run out of top speed on the track-- but the gear becomes usable.
-- New 3rd gear at about 1.65
-- existing 3rd becomes 4th
-- New 5th gear at about 1.117
-- existing 5th becomes 6th
Gives best spread and makes the ratios closer and more usable. Not to tall a 6th for cruising and you are never going to run out of top speed on the track-- but the gear becomes usable.
11-02-2009, 02:57 PM
#33
I like the re-use of this approach. Saves $$$. But it doesn't address the 1-2 RPM drop which is my biggest issue with the stock gears. Perhaps there are TWO ideal geariing solutions - one for the track (close 2-6), one for street (less 1-2 RPM drop, tall 6, whatever else needs to be adjusted in the middle).
You are correct. The needs of the street car are different than those of the track car. I think that is why Erik opted to create a unique thread for the "street" version. A streetcar will definitely benefit from the race setup, but it will not address what we feel is the greatest shortcoming in the gearbox for the street.
Erik,
I like your proposal but don't like the R&P change due to cost reasons and also am leery of any first that is taller than what I have.
I completely agree that a one size fits all approach here probably does not work. I know what the correct approach is, but honestly can't afford it. Therefore, I have to decide whether what I can afford will work, or if I need to leave the 'box alone. Others willing to spend the $$$ can do it "right" and get a killer box. Fortunately for me, I can experiment a bit more freely because I'm not paying a mechanic to swap parts.
I really appreciate your input and will certainly contact you when my reserves of disposable income begin to grow again. Then we can determine the option that will work for ME. I'm hoping the 2nd and 3rd regear option will work but only the graphs will tell...
Thanks!
11-02-2009, 04:43 PM
#34
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Personally I would never use an 8:32 R&P in a road car because of the 1:4 wear pattern of the teeth - putting it bluntly they wear out a lot faster than the standard R&P which constantly varies the mesh of the teeth.
My advice would be similar to Bill's in that I would definitely change out 1st & 2nd to be more active, then look to achieve sequentially reducing rpm drops through the rest of the gears. In practise this usually means that you get approximately even mph changes through each gear. Around 50mph in 1st gear is ok for street use, it's approximately what Porsche fitted to the 993RS as standard with either the dual mass or lightweight flywheel.
My advice would be similar to Bill's in that I would definitely change out 1st & 2nd to be more active, then look to achieve sequentially reducing rpm drops through the rest of the gears. In practise this usually means that you get approximately even mph changes through each gear. Around 50mph in 1st gear is ok for street use, it's approximately what Porsche fitted to the 993RS as standard with either the dual mass or lightweight flywheel.
11-02-2009, 04:45 PM
#35
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I am confused as to who is who here. Gt Gears in Boulder and Gbox also in Boulder? Is this different than Paul's outfit Guard Transmission?
11-02-2009, 05:46 PM
#36
11-02-2009, 08:01 PM
#37
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My favorite thread on re-gearing is this one.
https://rennlist.com/forums/993-foru...hlight=gearing
GR8nine93 replaced 2 through 4th with 16:38 = 2.375,18:32 = 1.78 ,23:27 = 1.17.
Wonder if Bill can post up one of his famous graphs for this gearbox. I do not think it has been posted.
Eric, don't give up on us.
Thanks
https://rennlist.com/forums/993-foru...hlight=gearing
GR8nine93 replaced 2 through 4th with 16:38 = 2.375,18:32 = 1.78 ,23:27 = 1.17.
Wonder if Bill can post up one of his famous graphs for this gearbox. I do not think it has been posted.
Eric, don't give up on us.
Thanks
11-02-2009, 08:37 PM
#38
My favorite thread on re-gearing is this one.
https://rennlist.com/forums/993-foru...hlight=gearing
GR8nine93 replaced 2 through 4th with 16:38 = 2.375,18:32 = 1.78 ,23:27 = 1.17.
Wonder if Bill can post up one of his famous graphs for this gearbox. I do not think it has been posted.
Eric, don't give up on us.
Thanks
https://rennlist.com/forums/993-foru...hlight=gearing
GR8nine93 replaced 2 through 4th with 16:38 = 2.375,18:32 = 1.78 ,23:27 = 1.17.
Wonder if Bill can post up one of his famous graphs for this gearbox. I do not think it has been posted.
Eric, don't give up on us.
Thanks
11-03-2009, 01:00 AM
#39
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11-03-2009, 01:57 PM
#41
Nordschleife Master
Gbox is a builder, in addition to manufacturing certain niche specialty parts. They are also a Guard Transmission customer.
Guard Transmission is essentially the same business it was when Paul was at the helm, a manufacturer of gears and LSDs for Porsches.. In fact, Paul is still a minority partner in the new business. Since Paul is returning to Hawaii it made no sense to move me and my family to CA. So, instead we moved the business to me.
It can get a bit confusing, since both myself and the owners of Gbox (not to mention their employees) ALL have worked for both Carquip and Powerhaus at one time or another over the last decade. It's one of those fringe markets that develops it's own group of specialists.
Regards,
Matt Monson
Guard Transmission LLC
11-03-2009, 01:58 PM
#42
Nordschleife Master
11-03-2009, 02:10 PM
#43
Rennlist Member
Given the experts involved in that particular example, I would think that it would be a good setup. I guess it works well for that individual but might not be great for others (big 3-4 drop not good on track?).
11-03-2009, 03:02 PM
#44
That's what due diligence is all about. Before I embark on any project I try to learn as much as I can about it.
11-03-2009, 03:56 PM
#45
BTW, I just wanted to say thanks to Bill for the awesome charts and graphs. I have printed out most of these to get a feel for what I would be looking for when the time comes.