Does having a supercharger mean a higher rear end gear ratio is better than N/A?

[Makahveli]

I've had my explorer for over 10 years now, back then I planned on having and upgrading to 33-35 inch tires and lifting it as high as I could so I then installed 4.56's gear ratio's at front and rear. I did gears early because when I got the explorer it came with 32's with just the stock 3.27 gears on it. Of course throughout the years my thoughts on the ex have changed and now I'm happy with the look of 31's and 32's on 22" rims and also reduced the lift I had on it and did major engine work to it. It's now just a street driven ex and with 4.56's it revs/raps out so fast and I wanna fix the ratio back to a daily driver but still good performer type. I was thinking of 4.10's but is it enough to tell a difference? A local drivetrain shop I went to told me with a supercharger go another step lower which I think is 3.73's he agreed to. I was looking for the 3.91 or 3.93 gear set but can't find one for the front. any knowledge or opinions you guys can give me? Thanx in advance!!!

 

[Dono]

Id think you have a ton of power right now, so going with a lower ratio wont hurt you. It will make your truck slower though.

 

[Maniak]

I would say it would make it "less quick", but faster. By faster, I mean faster at a given RPM.

If/when we do the Forced induction to the mustang we may bring our gear ratio back down to 3.31 to get the RPMs back down. We won't need to be spinning 2700 rpms when crusing at 80 mph all day long if we have more power.

~Mark

 

[Makahveli]

yeah it have alot of torque now, like when I try to race joe nobody at a stop light I always beat them off the light then they catch up I shift up leave them again then they catch up again and i shift up and leave them again over and over again.

 

[Dono]

The new gears will help your gas mileage if you care. Your motor is plenty strong to be able to pull its self quickly with the 3.73's im sure.

Isn't 3.73 stock ratio on 2nd gen's with 15 inch rims and 235/75R15's? If so, thats what I have and I wouldn't have problems with 31"s or 32" tires Im sure.

 

[Makahveli]

I'm not sure at all on the second gens, but I do plan to pul a rear end from one at a junkyard as a rear disc conversion. Having 3.27's with a 5 speed I went through 2 clutches in 4 years.

 

[Anime]

4.56's seem to be the thing for 33's, so they might be a bit much for 31-32's, especially if they're closer to 31 inches in diameter. Stock 3.73's with 31's are close to the 'factory' setup yours had with 28/29 inch tires and 3.27's.

Generally for street use, you want a middle-of-the-road ratio, which is not the low gears for off-road, or the tall highway gears for high speed/mileage. 31's are still a little taller than stock, so the 'performance' 3.73 gears would be good for higher speed, 4.10's if you want better takeoff.

The best thing to do might be to find out where the engine is now making it's torque, and doing the math with gear ratios, tire diameters, and engine RPM to figure out which gears will keep it below and up to that range.

You could also just re-gear the rear end for now with what you choose, and just not use 4WD (obviously no need to on the street anyway), then if you decide to switch again, you only have to get the front done once rather than twice.

The rear end 3.73 gears are rather inexpensive, even new from Ford, and obviously even less used, so those might be the ones to go with. If it's too sluggish, you know 4.10 is what you want.

Really it depends on how you're using it. If you're drag racing, you want the higher gears so when the supercharger catches and spools up, you can keep going to 75-85 and maybe a bit beyond. Those low gears (especially 4.56's and maybe even 4.10's) work great for low end, but you run out of gear (or risk the engine flying apart at high RPM) before you even hit the speed limit.

The tradeoff is that the high gear that works great under boost might feel sluggish under regular use, and the ones that feel right just driving around might be too low to take full advantage of the supercharger. You'll have to decide what's more important or what feels best to you for how you use it.

 

[jd4242]

4.10 all day for your tire and wheel size.you go any lower you will regret it.you need that tq for those heavy rims,as you know they eat up alot.if you went back down to a 16 or even 18 you would gain a ton of power and then i would suggest 3.73 with 5speed.im going to be running 4.88 and 33s street tire.whats your top speed in 2nd and whats you rev limiter set to?do you know where you make most power at?you must have some long roads around there,i can hit 88mph in 2nd at 6,000 rpms(4.88&36)i need more gear(5.13) or smaller tires

 

[Makahveli]

does anyone know about if there is a gear ratio for our fronts that will match with the rear ends 3.9sumthing gears?

 

[jd4242]

does anyone know about if there is a gear ratio for our fronts that will match with the rear ends 3.9sumthing gears?

Nope 3.73or4.10

 

[jd4242]

I would find a nice 2nd gen with 4.10.do the swap and if its still to high then 3.73 are dime a dozen.i even have a set laying in the garage.

 

[Makahveli]

I would find a nice 2nd gen with 4.10.do the swap and if its still to high then 3.73 are dime a dozen.i even have a set laying in the garage.

Doubt I can find a 4.10 sitting already in an axle, I went to the track last month was was dissapointed at best running high 18's. Then again I could learn to shift better being my first time ever at the track and I was told at sea level it would be in the 17's too!

 

[jd4242]

Doubt I can find a 4.10 sitting already in an axle, I went to the track last month was was dissapointed at best running high 18's. Then again I could learn to shift better being my first time ever at the track and I was told at sea level it would be in the 17's too!

O wow that is slow.i ran 18 flat NA with 3.73 and33s.you was tuned at that altitude and its fuel injected,shouldn't make HUGE difference.your be even slower on the track if you change your gears out.you should be running easy in the 15s with your setup.

 

[Makahveli]

my shifting was bad too, but yeah it chirped every time i shifted but rapped out quickly in each gear. I was tuned at this altitude but the shop i used aimed more at being conservative (reliability)than max power so I guess thats good in a way so they only did two out of the allowed 4 tunes the chip will hold.

 

[Makahveli]

JD you really think 5.13's will get you a faster time? And when my chip was don the rev limiter was turned off. Are you running disk brakes on your rear axle yet? My rears are pretty useless, makes me not even want to drive the explorer right now, This multple project thing sure is creating alot of worries....

 

[Makahveli]

Think I just answered my own question.... I bought this wheel and tire combo from a guy that had a F150 (late 90's body) and it wasn't lowered or lifted. So I'm assuming my tire size is close to their stock size, if so I'll try and see what they use for there supercharged trucks, I'm not sure but off the back I'm assuming the lightnings have a smaller tire diameter but I'll look into those too!

 

[jd4242]

JD you really think 5.13's will get you a faster time? And when my chip was don the rev limiter was turned off. Are you running disk brakes on your rear axle yet? My rears are pretty useless, makes me not even want to drive the explorer right now, This multple project thing sure is creating alot of worries....

For my 36x14.50 tires yes 5.13 would make me faster.my gears are to long and 5.13 would get me through them faster and keep me at my peak rpm range.i cant afford to redo gears so im getting a set 33s street tires.4.88 &33 is perfect for my truck.yea i have cross drilled and sloted rotors on all 4.

 

[Dono]

At the track, what were you 1/8 mile times? They should have been killer low.
Im just trying to figure out if you run out of gearing/high rpm rev's before the end of the 1/4 mile.

You should be super quick in the 1/8 mile. If you run out of steam towards the end of the 1/4 mile then a gear change would benefit your times.

Looking at your specs, Id have thought you would be way faster than you are. Of course, I have no idea what my times are either. Still though, high 18's/low 19 seconds is close to factory with no mods isn't it?

 

[jd4242]

Think I just answered my own question.... I bought this wheel and tire combo from a guy that had a F150 (late 90's body) and it wasn't lowered or lifted. So I'm assuming my tire size is close to their stock size, if so I'll try and see what they use for there supercharged trucks, I'm not sure but off the back I'm assuming the lightnings have a smaller tire diameter but I'll look into those too!

You cant compare the two at all.one is a v8 &you have 20" rims .as far as i know you cant remove the rev limter on our trucks,just raise it and i would go over 6500 rpms.that's if you have you motor blueprinted and balanced.

 

[jd4242]

At the track, what were you 1/8 mile times? They should have been killer low.
Im just trying to figure out if you run out of gearing/high rpm rev's before the end of the 1/4 mile.

You should be super quick in the 1/8 mile. If you run out of steam towards the end of the 1/4 mile then a gear change would benefit your times.

Looking at your specs, Id have thought you would be way faster than you are. Of course, I have no idea what my times are either. Still though, high 18's/low 19 seconds is close to factory with no mods isn't it?

Before i did 422&high compression and still had 33&3.73.i ran 3.05 in 60ft-11.76@1/8 & 18.1@1/4.if you compare that to what a stock ex runs you will see my 60ft and 1/8 mile are super slow but on the top end i made up for it.i have plenty of top end gear,i need to get up out the hole faster and stay in peak rpms range 3500-4500