3.90 gears???

lptheory96 · May 6, 2006

I saw on partshopper.com a set of 5.0 brand 3.90 gears, Been thinkin gof gearing down my 2004 GT 40th ann.... 3.73 seemed too high for the money, 4.10 seems like it'd be too steep (my old 90 5.0 lx had trouble drving on interstate, (it was auto) [After the od burned out it was useless]

ANYWAY.. 3.90 would seem perfect, Any idea why I dont see more 3.90's.. just an odd gear not too many ppl like? What do you think of the gear?

the98stang · May 6, 2006

lptheory96 said:
I saw on partshopper.com a set of 5.0 brand 3.90 gears, Been thinkin gof gearing down my 2004 GT 40th ann.... 3.73 seemed too high for the money, 4.10 seems like it'd be too steep (my old 90 5.0 lx had trouble drving on interstate, (it was auto) [After the od burned out it was useless]

ANYWAY.. 3.90 would seem perfect, Any idea why I dont see more 3.90's.. just an odd gear not too many ppl like? What do you think of the gear?

I believe only one company makes the 3.90 (motive), which makes them rare. What are your future mod plans? If you plan to stay naturally aspirated, get the 4.10's. If not, stick with the 3.73's.

Crzyhrse · May 6, 2006

If I ever decide to finally put some other gears in, I'm going with the 3.90's. Not many people use them, but I think that gear would suit me fine.

lptheory96 · May 6, 2006

Agreed... For the guy 2 post above, all the mods in my mind are posted on my sig, as far as n/a.. I figured I would be.. The day I spend $2000 on a s/c is the day I probally break my drivetrain and buy new tires every week, What is the issue with haveing 3.90's with a S/C.. Too much power being planted to the ground all at once? Constant tire spin w/o slicks and if you put clicks on it just breaks the tranny? Never had a s/c but something tell sme that would make my daily driver not to daily drivable

helty · May 6, 2006

4.10s are so popular bc mod motors have a much different power band than the old 5.0s. 4.10 isnt too steep, some guys even opt for 4.30s.

Motive and Pro 5.0 make 3.90s.

the98stang · May 6, 2006

lptheory96 said:
Agreed... For the guy 2 post above, all the mods in my mind are posted on my sig, as far as n/a.. I figured I would be.. The day I spend $2000 on a s/c is the day I probally break my drivetrain and buy new tires every week, What is the issue with haveing 3.90's with a S/C.. Too much power being planted to the ground all at once? Constant tire spin w/o slicks and if you put clicks on it just breaks the tranny? Never had a s/c but something tell sme that would make my daily driver not to daily drivable

Many people on this board have supercharged daily drivers. They are safe, as long as the tune is dead on and the air fuel ratio is good across the rpm band. And yes, a supercharged 4.6 with 4.10 gears will have a tough time with traction. The car would be better off with 3.73's.

Outlaw97GT · May 6, 2006

You can't compare driving a 5.0 with 4.10's and a 4.6 with 4.10's.
2 totally different beast.

spederman · May 6, 2006

I just ordered a set of motive 3.90's from mustangtuning. I am having them installed next saturday. I'll put up a review next weekend.

I called one of the best tuners down here in Texas and asked him how he feels about being supercharged and 3.90's. He said 3.90's would work really well for my car. He said 4.10's is definately too steep with a S/C. I figure when i get one its going to be a centri, and those dont max boost till the higher rpms 3-6k, so still having a steeper gear for the low rpms should work out for it really well. I wanted 4.10's but i'll have a S/c within a year, why spend gear cash twice, i might as well get 3.90's and i'll be set when i get the supercharger.

I would love to hear a review from people that already have 3.90's. It seems like there's hardly any people that have them, there are no good 3.90 threads.

helty · May 6, 2006

If motive made 3.90s for FRPP, a lot more people would have them instead of 3.73s. A lot of guys are scared away from motive bc of the mythical "motives whine and FRPPs dont" theory. Thats BS. ANY gear can and will whine if not set-up and installed properly. FRPPs are easier to install too, so a lot of shops recommend them.

spederman · May 6, 2006

Yeah, that motive whine myth is false for sure. I was talking to the shop doing my install and he has done a ton of motive installs and not a single one whines. He said its all about how you install them and if you are measuring out all the parameters or not.

I still want to hear some feedback, people with these, post up please.:SNSign:

damacman · May 7, 2006

too steep heh? 4.10s are the purr-fect gear for any centri set up as they let you get into the boost nice and quick. Of course, this is an issue with stock tires. I would concur that 4.10s are a little too steep with positive displacement blowers though . . .

helty · May 7, 2006

I think 3.90s will be great with a centri. More than 3.73s but not too much. Not that 4.10s are too much, but the 3.90s will help with traction compared to the 4.10s, and I dont think the accelleration difference will be too significant.

LI98GTStang · May 7, 2006

helty said:
If motive made 3.90s for FRPP, a lot more people would have them instead of 3.73s.

This is true. I just had motive 3:90s installed by my local mustang speed shop and they did a great job - no whine. The shop only carries FRPP gears and also has a very good deal on the gears and installation, so it would have been much easier for me to get either 3:73s or 4:10s. I believe a lot of shops are this way.

I had to order and bring in the Motives and also accept that the shop wouldn't warranty the install.

LI98GTStang · May 7, 2006

lptheory96 said:
I saw on partshopper.com a set of 5.0 brand 3.90 gears, Been thinkin gof gearing down my 2004 GT 40th ann.... 3.73 seemed too high for the money, 4.10 seems like it'd be too steep (my old 90 5.0 lx had trouble drving on interstate, (it was auto) [After the od burned out it was useless]

ANYWAY.. 3.90 would seem perfect, Any idea why I dont see more 3.90's.. just an odd gear not too many ppl like? What do you think of the gear?

That's basicaly the same thought process that I went through. net-net 3:73s maybe not enough, 4:10s maybe too much (for my NPI heads anyway), and 3:90s maybe just right. I'm still trying to get the speedo corrected and haven't taken it on any long trips as of yet, but my initial impression is that they are just as goldilocks hoped.

3.90 gears???

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