Ratios, tire diameter, final drives, oh my

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twinkletoes

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Has anyone or does anyone know of someone who has installed a 7 s.p. 2nd gen auto trans. in there 1st gen? I don't care if it's an fx, g or z.
If it's not reasonably($) possible, I suppose the h.r. would just have to go in with it.
 
fx35 awd 03-08's got 30.6" diameter tires, 3.69 final drive w/3.54 1st and 2.26 2nd gears producing 280/270 @ 4200lbs. w/a 1/4 mile of 15.7.
ex35 awd 2008 has 27.6" diameter tires, 3.69 final drive w/3.84 1st and 2.35 2nd gears producing 297/253 @ 3900lbs. w/a 1/4 mile of 14.8.
qx50 awd 2015 has 27.6" diameter tires, 3.13 final drive w/4.92 1st and 3.19 2nd gears producing 325/267 @ 4000lbs. w/a 1/4 mile of 14.2.

This may not be exactly breaking news to anyone, but nonetheless I find it interesting and thought I'd share. I could go on w/g's and 2nd gen fx/qx's, but my comparison w/the ex35 and qx50 is because their in my current weight class @ 4000lbs. Look at the top two, the fx and ex. The ex gives up a little torque but get a little hp in return. The torque must be more than made up for by the gearing. No big deal between 1st and 2nd gears BUT the tire diameter is 3 inches smaller. My question is, is it factor fixed into the final drive outcome of 3.69? I don't see how it could be. The only difference between the two is 300lbs, a modest shift in power and tire size. I highly doubt that rotating mass reduction (3" diam. smaller wheels) is responsible for that big a difference in acceleration.
The comparison between the ex and qx is just as odd, to me @ least, but in a different way. It's 100lbs. heavier (no big deal), has the same tire diameter yet a much weaker final drive. But look at the 1st and 2nd gears which are much more aggressive. Ain't no way 100 xtra pounds + 28 xtra hp/14 xtra tq is going to propel that thing .6 sec. faster. It's all in the gearing, hence so many gears, too make up for the lost mpg's.
An bone stock 03-08 fx35, all things being equal, with a similar tire diameter OR a more agressive r&p (27" tires on an fx wouldn't look too hot) with the 2nd gen trans, it would be solidly in the 14's all day long. Moded w/bolt-ons and tuned, low 14's, all day long. Modest quality f.i. w/ water inj., very low 13's to high 12's all day long. When did all the auto manufacturers figure this out, because they're all doing it, and who did so first? Go ahead, tell me where I'm wrong.
 
I think automakers have known this for a long time but the transmission technology wasn't there yet. It was 3 speeds forever and then 4, then 5 and now it went from 6-9 very rapidly. Even have 7 speed manuals now. It's really common sense that if the transmission can keep the engine in it's powerband longer it's better for performance and/or economy.

Also a lot of automakers don't make their own transmissions. For instance ZF makes an 8 speed basically used by everyone from BMW, to VW, to Chrysler, and on. So until the transmission maker is onboard, the theory really doesn't matter.

It would probably just be easier to swap in a diff with higher final drive. Or swap in the 6mt and higher final drive. There are trade offs but if you want a better 1/4 time... If you try to swap in the 7 speed not sure how you'd get the ECU to work with the TCM. I think that would be a bigger limitation than any of the hardware. It's easy to machine adapters, much harder to work on the ECU. Good luck if you try though.
 
Not much unless you were really into drag racing and wanted to drop your times. To me if you really want to run the 1/4, the FX is a poor choice as a starting platform.
 
shadow191 said:
I think automakers have known this for a long time but the transmission technology wasn't there yet. It was 3 speeds forever and then 4, then 5 and now it went from 6-9 very rapidly. Even have 7 speed manuals now. It's really common sense that if the transmission can keep the engine in it's powerband longer it's better for performance and/or economy.

Also a lot of automakers don't make their own transmissions. For instance ZF makes an 8 speed basically used by everyone from BMW, to VW, to Chrysler, and on. So until the transmission maker is onboard, the theory really doesn't matter.

It would probably just be easier to swap in a diff with higher final drive. Or swap in the 6mt and higher final drive. There are trade offs but if you want a better 1/4 time... If you try to swap in the 7 speed not sure how you'd get the ECU to work with the TCM. I think that would be a bigger limitation than any of the hardware. It's easy to machine adapters, much harder to work on the ECU. Good luck if you try though.
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I discussed this with a shop owner today after the tune. What you mentioned regarding the ecu/tcm would be an, if not the issue. He suggested swapping the 3.5 w/trans for the 3.7 w/trans along w/the ecu and sensors. That sounds like a pain in the ass. I've got some things to think about and hey shadow191, thanks for the reply!
 
shadow191 said:
Not much unless you were really into drag racing and wanted to drop your times. To me if you really want to run the 1/4, the FX is a poor choice as a starting platform.
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To myron02, the point is that transmission is far superior in terms of it's agressive gearing than the 1st gen 5 spd. a.t.. It's the transmission that's responsible for damn near 1/2 the reason why a stock qx70 is a second faster than a stock gen 1 fx35. Considering advances made from the 1st to the 2nd gen., bringing my old and busted (but much better looking) up to par with the new hotness (they butchered the fx, just killed it) will provide me with a great increase in acceleration without adding stress to anything, just simply multiplying the torque to the wheels. Without this aggressive gearing = light weight/built fx in the mid-low 12's. With this aggessive gearing = light weight/built fx in the 11's, especially assuming the 7 speed, one might as well up the final drive ratio.
To shadow191, you're right but I don't want to run the 1/4 mile as a pass time or hobby. Sure, on rare occasion for fun. I want to take what is essentially a free fx to me as I've had it for 11 years and couldn't get what, 14k for it now, and turn it into what I'd like it to be rather than buying another auto of whatever sort. If I wanted to go the 1/4 fast and cheap, I go american muscle all day long, like I did years ago. There's just something about taking a fast car and making it faster that to me is just boring. It's expected. Thanks for showing interest and replying!
 
twinkletoes said:
To myron02, the point is that transmission is far superior in terms of it's agressive gearing than the 1st gen 5 spd. a.t.. It's the transmission that's responsible for damn near 1/2 the reason why a stock qx70 is a second faster than a stock gen 1 fx35. Considering advances made from the 1st to the 2nd gen., bringing my old and busted (but much better looking) up to par with the new hotness (they butchered the fx, just killed it) will provide me with a great increase in acceleration without adding stress to anything, just simply multiplying the torque to the wheels. Without this aggressive gearing = light weight/built fx in the mid-low 12's. With this aggessive gearing = light weight/built fx in the 11's, especially assuming the 7 speed, one might as well up the final drive ratio.
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I know what you're saying, but I think that you can have a faster car for less money by going FI. That's why I was asking what's the point of transmission. Since I doubt you will be able to swap that 7 speed tranny, due to mechanical stuff, computer stuff and/or funds. There is a SC for sale in the market place, buy it and go fast.
 
Understood, do what makes you happy. It would be cool if you got the 7 speed working. I originally had big plans for the FX, was going to boost it and so on. Then got a modded 335 and realized the FX was never going to be remotely as fast and I was going to ruin it by trying to make it that way. So I've left the FX as the city cruiser with just bolt ons and aggressive wheels. I get trying to make a regular car fast (had a custom turbo Maxima) but there are so many tradeoffs that you do have to take them into consideration. Also I took a ride in a friend's X5M and realized my FX wasn't ever going to be that so that factored into the decision to leave well enough alone.
 
myron02 said:
I know what you're saying, but I think that you can have a faster car for less money by going FI. That's why I was asking what's the point of transmission. Since I doubt you will be able to swap that 7 speed tranny, due to mechanical stuff, computer stuff and/or funds. There is a SC for sale in the market place, buy it and go fast.
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I cannot argue with you. There's no doubt FI will do me more good than this trans., well, unless it's a low-stage stillen and which brings me to my point. I could max everything out to the point where I could do no more, the point to where if I pushed for one more hp out of the vq, pop! Now, being the reasonable person I am, I want power but not to the point where reliability is an issue. I've planned on a stroker + no2. I'll be bummed if this isn't what I end up doing, and I don't see why I would change my mind, but I'll stay flexible. Throw this trans. in the mix and guess what, I just got 1/2 sec. + more acceleration without pushing the trans. or engine. I can have someone make the stock 5 speed stronger and shift faster which many have done and I may have to do as well. I find out in the not-too-distant future.
Put it this way, take Rookies fx, toss in this trans and some modestly sized tires = high 11sec. suv all day long and the same with jumbosrule. Thanks myron02.
 
shadow191 said:
Understood, do what makes you happy. It would be cool if you got the 7 speed working. I originally had big plans for the FX, was going to boost it and so on. Then got a modded 335 and realized the FX was never going to be remotely as fast and I was going to ruin it by trying to make it that way. So I've left the FX as the city cruiser with just bolt ons and aggressive wheels. I get trying to make a regular car fast (had a custom turbo Maxima) but there are so many tradeoffs that you do have to take them into consideration. Also I took a ride in a friend's X5M and realized my FX wasn't ever going to be that so that factored into the decision to leave well enough alone.
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For sure, I get and agree w/your sentiment. This is why it's so rare to see something like the fx's or anything else w/30-100k worth of customization done. It's daunting. I've done it before but that was a mustang which had multiples of everything one would ever want. The hard part was choosing. The FX is a rare bird in that it shares a platform w/the 350/g and gained a following.
It's not hard to forget that the fx45 was the fastest suv/crossover out there for awhile, and the fx35 wasn't so far behind. The fx started this race. Automakers all got wood when it came out. I know it and so did I. I remember seeing one in 2002 in CA for the first time. I was like damn, that's radical.
My goal isn't to have the fastest fx. Honestly, I cannot put the fx back at the top of the food chain, but I can with mine and can do so in a detailed, functional and professional way that will do it justice. I just need to shave a few seconds off.
As far as your fx never being as fast as an m series, whaaaat??? Why's that? The things (x5m) a pig, it's a german fucking tank man (I"m part german). Sure, big power but my God, could they not have made it any heavier? Now there's an auto to hold onto for awhile and watch the bills add up. Best to trade it in before the warranty runs out imo.
Recently, I read an article in an auto mag. where a guy popped his 7k mile gtr, stock. Shit happens. There's no reason why one cannot give a respected shop 30k, look the other way, no participation whatsoever, and have an fx35 that will surpass an m. Say you paid 40k 10 years ago for your fx, put 30k in for a total of 70. Take the 30+ difference and buy some stocks.
Now an x5 m w/water/meth + a tune's gonna dip into the 11's just a bit. Add a bunch of goodies to an fx, don't take anything off and one might forget what one set out to do, naa mee?
 
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