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New Owner
Hi Everyone -
Been scouring for a few months but am now an official owner of a Superformance Mark III (SPO #2632). I will be picking up the car on 9/15/07 and will be doing the install myself (with help from a good friend who has one under his belt). The specifics: Black and Titanium 15" Wheels Roush 402SR Tremec TKO 600 (undecided on the overdrive ratio) I look forward to making some new friends and learning from those who have been there before. Thanks to jwoodard, BLUE427, CBattaglia, and wtm442 for answering some of my questions prior to my purchase. |
Ekrupa,
Glad to hear you are joining the fraternity of owners. Go with the .82 overdrive. I really think you will be much happier in the long run. If you have time why don't you come to St. Louis and check out Run and Gun. The dates are October 10-13, 2007. You are welcome to participate but you probably won't be ready by then. It would give you a chance to meet some of the Cobra, GT40, Coupe, and other kit owners. Several are from your area (Steve Pass (cobra), Jim Pass (corvette), Fran Hall (RCR Mfg). Here is our web site and be sure and check out our forum: http://www.runngun.net Congratulations again! Clois Harlan |
Unless you plan on lots of highway cruising, I too suggest the .82 OD. I have had both and preffer the .82 all day long. In BDR #198 I rarely used 5th (it had the .62) even when on the Hwy.
Also, your rear axle ratio will have a significant contributing factor of which ratio to use... |
Which rear end do you have and will you primarily track the car or do a fair amount of highway driving? with a 3:54 or 3:77 rear the OD will be nice for highway driving at 80 mph and rpm's (without checking a calculator) in the 2200-2500 rpm range. On a track, 4th gear at 6000 rpm's will get you to 130 mph, so unless you're on a long straight, you won't use 5th very much. I am going with a tko600 and .63 OD for the highway benefit, witha 3.54 rear.
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I have a 0.68 OD gear Tremec with 3.73 rear gears. In 5th gear at 100 MPH, its only reving 3000 RPM. The 0.68 gear is great for good gas mileage on a loooooong highway trip. I do not like to go over 65 MPH on highway (too much wind buffeting) so the RPM's in 5th gear are about 1800 RPM at that speed. It also cuts down on the noise, but I still use ear plugs on a long highway trip.
There are advantages and disadvantages of both overdrive ratios. If you intend top do a lot of highway driving, go with the 0.68. If very little highway driving or if you intend to race the Cobra, go with the 0.82. If you are going with a numerically low rear gear, definitely go with the 0.82. Here is a good calculator. Play around with the various numbers to see what RPM's you will have at different speeds in various gears. http://www.secondstrike.com/Technical/GearCalc.asp At 7000 RPM, my Cobra should be going 221 MPH in 5th gear. Too bad its an airplane at 160 MPH. |
Thanks Everyone. Looks like I need to find out what rear end gear the car comes with...assuming all the Superformance come with the same but maybe thats not the case.
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Superformance Transmission Ratio
Well I found my answer on the rear end ratio...now for some advice. Since the rear end ratio is 3.46, and I will be driving mostly on the road versus the track with some long distance driving, .82 or .64??? Any thoughts from someone who has driven both?
Thanks! Quote: |
I've only had the 0.64 Tremec. The drop in revs from 4th to 5th gear is a lot.
Using the calculator link, you would be doing 72 MPH with the 0.64 at 2K RPM or 57 MPH with the 0.82 at 2K RPM. When I'm on the highway, I'd like to see the revs at 2K and above, because when the traffic slows down, my RPM's drop down so much that I have to shift into fourth or listen to the engine lug at those low RPM's. And the shift pattern of a Tremec from 4th to 5th (or visa versa) is not the best. One time I downshifted from 5th very fast and hit second instead of 4th. :o :o Can you say Compression Rubber? Yow! Therefore, I only use 5th on the major highways when I'm doing at least 65 MPH. With your lower numerical rear end as compared to mine, I would suggest the 0.82 overdrive. You'll be at 2K RPM at 57 MPH and 2500 RPM at 71 MPH. Good RPM's for highway cruising. Of course, if you live in a state without speed limits and want to cruise at 100 MPH, then go with the 0.64 :LOL: :LOL: :LOL: |
Thanks Warren. You have made my decision for me... .82 it is. If it had the 3.73, i would have chosen the .64. By the way, I just received my Poly mounts from Olthoff Racing...wow are they solid!!! Glad i made the choice to upgrade those. The pics posted on here dont do them justice as far as weight and quality. As i start my installl project, I will post some pics along the way.
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Sounds like your really moving right along. My "local" rep is in NY and after talking with him twice on the phone ... sorry, no business from me.
My Cobra was originally purchased by the first owner from Olthoff. I've also purchased parts from them and talked numerous times with Dennis. Fantastic service. Many of the parts developed by Dennis Olthoff are now standard construction on an SPF. |
FWIW:
I have the 15" tires and a .64 (actually .68, I think) fifth gear. My car originally came with 3.73's and first gear was pretty much useless. I considered changing to 3.55's but was persuaded to drop down to 3.27 which was the perfect choice for me and for the way I use my car. I put on about 5K miles per year with a fair amount on Interstate highways, although I usually try to take two lane roads whenever possible. I have a pretty mild-mannered motor, so I can use 3rd or even 4th gear in town and can pull 5th gear from well below 50 MPH without any fuss as long as I don't try to accelerate too hard. If I tracked my car, I might not be happy with the taller OD but it's great for the way I use it. I like being able to putt along at 60-70 MPH at 1,800-2,000 RPM and haven't ever wished for a lower 5th gear. Congratulations and good luck with your new car. Lowell |
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