3.90 Final Drive Ratio - Gauging level of interest


nota4re

GT Owner
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Le Mans 2010 Supporter
Feb 15, 2006
4,281
OK for those of you "forum old timers" who missed out and for those of you who perhaps are too new here to remember, I'm asking for a show of hands of who may be interested in a new (3.90) final drive ratio for your FGT. If you want to learn more about this mod, please use the search capability. In summary, Ford knew that the magazines testing the GT would undoubtedly benchmark 0-60 times against rivals. To help mitigate human error, they equipped our beloved GT's with an unusually tall final drive ratio which enabled the GT to perform 0-60 acceleration tests using only 1st gear. Fortunately, our GTs have exceptional low-end torque and over time we probably can easily forget how tall the GT is geared.

Several years ago Stillen teamed with Ricardo and offered a limited number of 3.90 final drive kits for owners. In a relatively short period, they sold-out. I had the opportunity to briefly drive a GT with this gear set a couple of years ago. I still remember this experience. The car is a LOT more playful and energetic. 3.90 owners are welcome to chime in here as I would welcome input - both good and bad. I'd be pretty certain that those lucky few who did this mods have absolutely no regrets.

At Cool Tech, we have teamed with a thoroughly experienced transaxle-only race shop. 30+ years in the business. A shop that the OEMs go to in the US. They are extremely qualified and familiar with the Ricardo. The bottomline is that if we can amortize costs over ~12 or more firm orders, we can offer owners this mod. Approximate cost would be $10,000. Cool Tech would R&R the transaxle and the aforementioned transaxle shop would do the gear change. Cost would be lower for those that would find it easier to ship us their transaxle.

Chime in if you would have an interest.
 

bonehead

GT Owner
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Aug 18, 2012
2,827
Houston, TX
Cool stuff, Kendall!
I just did a quick search and found the original thread which provides a good bit of info. (no, I'm not doing it for cost alone, but it is tempting!)

http://www.fordgtforum.com/forums/showthread.php/6774-Stillen-3-90-Gear-Info
 

BlackICE

GT Owner
Nov 2, 2005
1,416
SF Bay Area in California
A great mod!

The car drives more like it should, stock 1st always felt too high. It did slow me down at Mojave through, had to make a shift into 6th. I shift much slower than Bonehead and lose 2 to 3 MPH during the shift. :ack
 

Lorenzo

GT Owner
Mark II Lifetime
Dec 28, 2008
626
U.S.A.
Most of my driving is in town or within a few miles from home so they have worked out perfectly for me. I wouldn't trade back that's for sure.

I believe the original run of these was 25 and some of the cars with them are no longer on the road. Currently 20 of us left last I knew.
 

BM SoCal

GT Owner
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Jan 2, 2009
240
Orange County, CA
I'd be in Kendall. Need to get in touch with you to get routine servicing done too.
 

FBA

GT Owner
Dec 5, 2010
1,672
31.022340° N / 44.846191° W
While I would love it, I feel 10k is steep and amount to justify that. I changed my Viper rear end from a 3.08 to a 3.55 for $2500 installed. Great mod and sorely needed on that car, but 10k even for a GT is what I would consider too steep for my interest.
 

CJ428

Farm GT
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May 21, 2008
1,475
NJ
Like BlackICE said it makes the car like it should have been in the first place. Much more responsive to petal input at any rpm in any gear.
 

PeteK

GT Owner
Mark II Lifetime
Apr 18, 2014
2,470
Kalama, Free part of WA State
For a few thousand, I'd be interested. For $10K, not so much.
 

fjpikul

GT Owner
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Jan 4, 2006
11,680
Belleville, IL
FYI, gas mileage goes down. Larson has it, loves it, but has to pull over for gas more often. He then has to speed to catch up to the rest of us casue we don't wait for him.
 

Gulf GT

GT Owner
Mark II Lifetime
Feb 9, 2006
1,539
California
First gear in the stock car is way too tall. The 3.90 change was one of the best mods I did to the car, much more playful on the street. Stillen swore by it on the track. All around made the car better to drive. Should have come this way from the factory. Looking back I would do it before adding more power even. Not so great for mile events or high speed runs, but lovely for everything else.
 

PL510*Jeff

Well-known member
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Nov 3, 2005
4,900
Renton, Washington
FYI, gas mileage goes down. Larson has it, loves it, but has to pull over for gas more often. He then has to speed to catch up to the rest of us casue we don't wait for him.


your are correct Frankie….best mod I have on my GT along with Stillen HD clutch. Mileage does go down a bit, +- 2-3 less on highways.

And of course you wouldn't wait! Something about the ice melting for the drinks you ordered to be waiting for your arrival.That's what Mikey said and seconded by Storm kitten.

See you in October.
 

nota4re

GT Owner
Mark IV Lifetime
Le Mans 2010 Supporter
Feb 15, 2006
4,281
For those of you commenting on the price - I agree with you. I just don't want anyone to think it is us doing the "gouging". The preliminary quotes for such a small run of gear sets suggests that they might be in the 7500-8000 range just for the parts. Then you have the transaxle R&R, and the labor to tear down the transaxle and install the gears. In summary, what is driving the costs (by far) is the custom manufacturing of the gears. Again, all of this is prelim but I just wanted to set expectations....
 

bonehead

GT Owner
Mark II Lifetime
Aug 18, 2012
2,827
Houston, TX
For those of you commenting on the price - I agree with you. I just don't want anyone to think it is us doing the "gouging". The preliminary quotes for such a small run of gear sets suggests that they might be in the 7500-8000 range just for the parts. Then you have the transaxle R&R, and the labor to tear down the transaxle and install the gears. In summary, what is driving the costs (by far) is the custom manufacturing of the gears. Again, all of this is prelim but I just wanted to set expectations....

Price is pretty close to what Stillen was charging with the initial run.

Way before my time, so there is probably an obvious answer. But will Riccardo not do another run? They've already done the R&D with proven results. Why reinvent the wheel?
 

paulo5656

GT Owner
Feb 18, 2006
85
with trans r and r how much?
 

nota4re

GT Owner
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Le Mans 2010 Supporter
Feb 15, 2006
4,281
Way before my time, so there is probably an obvious answer. But will Riccardo not do another run? They've already done the R&D with proven results. Why reinvent the wheel?

All I should say is that there are multiple options... and I'm very impressed with the contacts we've been able to develop. However, the first step is to see what the level of interest is. If/when we can get past this step then we can get serious about the various options and the pros/cons of each. So far there is consistently positive if not rave comments from owners with this mod but only 1 person expressing a serious interest.
 

Brombear

GT Owner
Mark II Lifetime
May 16, 2013
1,405
Frankfurt Area, Germany
Can anyone tell what is happening to final speed, how much is going to be lost ?
 

FBA

GT Owner
Dec 5, 2010
1,672
31.022340° N / 44.846191° W
From the thread back in 2007 --

Factory 3.3 Ratio Redline Speeds
1st: 62mph
2nd: 95mph
3rd: 131mph
4th: 171mph
5th: 210mph
6th: 255mph

STILLEN 3.9 Ratio Redline Speeds
1st: 53mph
2nd: 81mph
3rd: 112mph
4th: 146mph
5th: 180mph
6th: 220mph
 

Brombear

GT Owner
Mark II Lifetime
May 16, 2013
1,405
Frankfurt Area, Germany
I guess this is a theoretical list at engine redline ... can't remember reaching 255 mph :)
 

Brombear

GT Owner
Mark II Lifetime
May 16, 2013
1,405
Frankfurt Area, Germany
Having read a bit through the old threads for me a whipple upgrade seems more desirable (both combined seem to call for serious traction problems)
 

BlackICE

GT Owner
Nov 2, 2005
1,416
SF Bay Area in California
Having read a bit through the old threads for me a whipple upgrade seems more desirable (both combined seem to call for serious traction problems)

Not if you add a traction control system.