Jag Rear Gear

[Russ Dickey]

Is the 3.31 rear-end ratio the standard for Unique cars? My 1997 FIA accelerates so slowly, and runs such a low highway RPM (1700 @ 60mph in 5th gear with Tremec 3550), that I'm wondering if my ratio is higher than that.

A local Cobra builder told me that he thought Uniques came standard with 2.80 or 3.00, and I just want to get a little more info. I'll try the old "spin the tire and watch the driveshaft trick", but it's probably pretty hard to tell when the possible ratios are that close.

Thanks,
Russ

Unique 289FIA - Viking Blue

[pgermond]

Russ,
I don't know if Unique has a "standard" ratio or not. I ordered 3:31's with mine and did the "spin the tire and watch the drive line" trick and it was easy to determine that's what I got (there is a noticeable difference between two revolutions and three-n-third). It's simple enough and dosen't cost anything - give it a shot. The five speed may be the issue.. I went with a top loader 4-speed.

Phil

427 Roadster
Southern Automotive FE
Toploader

Roseville (N.Cal)

[pgermond]

Russ,
I don't know if Unique has a "standard" ratio or not. I ordered 3:31's with mine and did the "spin the tire and watch the drive line" trick and it was easy to determine that's what I got (there is a noticeable difference between two revolutions and three-n-third). It's simple enough and dosen't cost anything - give it a shot. The five speed may be the issue.. I went with a top loader 4-speed.

Phil

427 Roadster
Southern Automotive FE
Toploader

Roseville (N.Cal)

[Copper01]

Russ,

When I ordered my 427SC deluxe pallet kit in December '02, the "standard" gear ratio was 3:31 and there was a no-cost option to have 3:54 gears. I picked the 3:54 even though Alan assured me that a 427 side oiler would have no problem getting me where I wanted to go with the 3:31 gears.

Ben
Unique 427
SA 427SO w/ Toploader
Guardsman Blue

[Copper01]

Russ,

When I ordered my 427SC deluxe pallet kit in December '02, the "standard" gear ratio was 3:31 and there was a no-cost option to have 3:54 gears. I picked the 3:54 even though Alan assured me that a 427 side oiler would have no problem getting me where I wanted to go with the 3:31 gears.

Ben
Unique 427
SA 427SO w/ Toploader
Guardsman Blue

[brfutbrian]

russ, from what ive read on the other forums, the opinion seems to be that 3.55 or 3.73 is the ideal rear end ratio with a tremec transmission. it seems to me 3.73 might be alittle too low a ratio unless you like to autocross. as far as being able to tell the difference between 2.8 vs. 3.0 by spinning the driveshaft , like phil said, youll have no trouble. its nearly a quarter turn differnce.
later, brian

[brfutbrian]

russ, from what ive read on the other forums, the opinion seems to be that 3.55 or 3.73 is the ideal rear end ratio with a tremec transmission. it seems to me 3.73 might be alittle too low a ratio unless you like to autocross. as far as being able to tell the difference between 2.8 vs. 3.0 by spinning the driveshaft , like phil said, youll have no trouble. its nearly a quarter turn differnce.
later, brian

[TurnpikeBoy]

<img src=images/icon_speech_ok.gif border=0 width=17 height=15 alt=Insert Speech Icon: OK>, gotta sound off on this one.

I paid extra to get 4.09's in my diff; with a 302 under the hood I wanted to give up as little as possible to youse bigblock people.

And it works. Big time. 0-60, hand-timed, is in the 3.3 -3.4 second range. With a Tremec 3550, .68 o/d final, 80 mph is about 2600 rpm. 60 mph in 4th is about 3000 rpm. Very comfortable to drive, either around town or out on the pike.

Monster torque will permit toploaders and 3.31 / 3.54 rears - but little motors NEED gearing to make up the difference. 3.73's with a big block might result in more wheelspin than you want but will curl your hair once it hooks up...3.73's with a small motor (re: under 351) are about the minimum that ought to be considered. Even in a light car there just isn't enough torque to keep you grinning - especially once you are at highway speed.

Go with 3.73 / 3.92 / 4.09 ratios and you will NOT be disappointed - either in acceleration, around town flexibility, or highway cruising (with o/d trans).
[:P]

Yeehah

[TurnpikeBoy]

<img src=images/icon_speech_ok.gif border=0 width=17 height=15 alt=Insert Speech Icon: OK>, gotta sound off on this one.

I paid extra to get 4.09's in my diff; with a 302 under the hood I wanted to give up as little as possible to youse bigblock people.

And it works. Big time. 0-60, hand-timed, is in the 3.3 -3.4 second range. With a Tremec 3550, .68 o/d final, 80 mph is about 2600 rpm. 60 mph in 4th is about 3000 rpm. Very comfortable to drive, either around town or out on the pike.

Monster torque will permit toploaders and 3.31 / 3.54 rears - but little motors NEED gearing to make up the difference. 3.73's with a big block might result in more wheelspin than you want but will curl your hair once it hooks up...3.73's with a small motor (re: under 351) are about the minimum that ought to be considered. Even in a light car there just isn't enough torque to keep you grinning - especially once you are at highway speed.

Go with 3.73 / 3.92 / 4.09 ratios and you will NOT be disappointed - either in acceleration, around town flexibility, or highway cruising (with o/d trans).
[:P]

Yeehah

[TurnpikeBoy]

One other thing. When Unique gets the rears from their supplier, the supplier puts a small aluminum tag under one of the cover bolts that has the installed ratio stamped into it.

Check that tag - it'll tell ya just what you have. Just an alternative to spinning your wheels.

;)

Yeehah

[TurnpikeBoy]

One other thing. When Unique gets the rears from their supplier, the supplier puts a small aluminum tag under one of the cover bolts that has the installed ratio stamped into it.

Check that tag - it'll tell ya just what you have. Just an alternative to spinning your wheels.

;)

Yeehah

[Brent]

What rpm range is your motor built and tuned to run at?

[Brent]

What rpm range is your motor built and tuned to run at?

[TurnpikeBoy]

Brent, I bought a long block 302 from Ford Motorsport with the B-303 roller cam; specs for that cam (degreed straight up) have it coming on at about 2500 - 2700 rpm and signing off at 6000 - 6100 rpm. I ran calcs in determining final drive ratio by knowing intended tire diameter and desired rev range. After this it's pretty easy to figure out what you want in terms of final drive.

Some people will tell you 3000 rpm in 4th. gear is too high; That's a matter of opinion - I personally do not have any discomfort with it. The drop in engine speed between 4th. and 5th. is 1000 - 1100 rpm - crank 'im up to 5500 in 4th and you're right back up on the cam to keep on hauling your meat. And - the 1st./2nd./3rd gear rush has to be felt to be believed - I can tell you that you hit the rev limiter in 1st. so fast (mine is set at 6200) that you have got to pay attention to the tach. 2nd. comes up almost the same way, and in 3rd. you can actually pay attention to where you're going.

I confess I have not wound out 4th. or 5th. gears yet....my cojones just not that big. If it really matters, 5600 rpm in 5th. is 166 mph - and I truly believe this is reachable. If your cojones are that big.

Yeehah

[TurnpikeBoy]

Brent, I bought a long block 302 from Ford Motorsport with the B-303 roller cam; specs for that cam (degreed straight up) have it coming on at about 2500 - 2700 rpm and signing off at 6000 - 6100 rpm. I ran calcs in determining final drive ratio by knowing intended tire diameter and desired rev range. After this it's pretty easy to figure out what you want in terms of final drive.

Some people will tell you 3000 rpm in 4th. gear is too high; That's a matter of opinion - I personally do not have any discomfort with it. The drop in engine speed between 4th. and 5th. is 1000 - 1100 rpm - crank 'im up to 5500 in 4th and you're right back up on the cam to keep on hauling your meat. And - the 1st./2nd./3rd gear rush has to be felt to be believed - I can tell you that you hit the rev limiter in 1st. so fast (mine is set at 6200) that you have got to pay attention to the tach. 2nd. comes up almost the same way, and in 3rd. you can actually pay attention to where you're going.

I confess I have not wound out 4th. or 5th. gears yet....my cojones just not that big. If it really matters, 5600 rpm in 5th. is 166 mph - and I truly believe this is reachable. If your cojones are that big.

Yeehah

[Brent]

You are right. These cars are ill when they start to catch alot of air and everybody better respect them. There is not alot of tubing above the frame rails to protect the pumpkin either. As far as gear goes I went for the 3.54 an the only time she hooks up is when I take my foot out of it.

Brent
427 S/C
402 FE
Toploader

[Brent]

You are right. These cars are ill when they start to catch alot of air and everybody better respect them. There is not alot of tubing above the frame rails to protect the pumpkin either. As far as gear goes I went for the 3.54 an the only time she hooks up is when I take my foot out of it.

Brent
427 S/C
402 FE
Toploader

[TurnpikeBoy]

<img src=images/icon_speech_yeah.gif border=0 width=29 height=15 alt=Insert Speech Icon: Yeah!>!!
That, amigo, is why you need a small block!

At 1500 rpm in 1st, I can put the throttle to the water pump and all that happens is: (1)the assend squats about 4", (2) the nose sails up about a foot, and (3) the passenger's head hits the rear deck even when warned. No display, no wheelspin, just hauls the mail.

Powershift second and just a smidge of wheelspin but still - that Godawesome acceleration. I have a buddy with an SPF, with 427s/o done by Olthoff and he cannot believe how this car accelerates in the low gears...he's used to lotsa tire smoke too.

'Course, by the time I'm wound out in 3rd. he's about to kick my butt pretty convincingly. Oh, well, there's a 408 stroker in the future - just gotta love small blocks.

:D:D:D

Yeehah

[TurnpikeBoy]

<img src=images/icon_speech_yeah.gif border=0 width=29 height=15 alt=Insert Speech Icon: Yeah!>!!
That, amigo, is why you need a small block!

At 1500 rpm in 1st, I can put the throttle to the water pump and all that happens is: (1)the assend squats about 4", (2) the nose sails up about a foot, and (3) the passenger's head hits the rear deck even when warned. No display, no wheelspin, just hauls the mail.

Powershift second and just a smidge of wheelspin but still - that Godawesome acceleration. I have a buddy with an SPF, with 427s/o done by Olthoff and he cannot believe how this car accelerates in the low gears...he's used to lotsa tire smoke too.

'Course, by the time I'm wound out in 3rd. he's about to kick my butt pretty convincingly. Oh, well, there's a 408 stroker in the future - just gotta love small blocks.

:D:D:D

Yeehah

[Brent]

Build'em light and wind'em tight. If I had a FIA it would be a Windsor stroker for sure but to have the 427 emblem on the side and a 302 under the hood just did not seem right. I guess a 427 Windsor would have been cool.

Oh well mabye next time (-:

[Brent]

Build'em light and wind'em tight. If I had a FIA it would be a Windsor stroker for sure but to have the 427 emblem on the side and a 302 under the hood just did not seem right. I guess a 427 Windsor would have been cool.

Oh well mabye next time (-:

[GeorgiaSnake]

I have the FIA car with 3:31 gear, 4 spd toploader and 396 stroker with many goodies. The car hooks up if I roll into the throttle and just hauls ass. If I hammer the pedal it lights them up and dances sideways. I usually shift at 5000 rpm as I still have the 5500 rev-limiter in it, no powers shifts are needed. I haven't come close to winding out 3rd or 4th yet - still learning the car and breaking in the motor (800 happy miles to date).

I can't imagine a shorter gear helping that much and highway cruising would suck.

Randy

Unique 289 FIA
Southern Automotive 396
Team III 16's
Brilliant Silver

[GeorgiaSnake]

I have the FIA car with 3:31 gear, 4 spd toploader and 396 stroker with many goodies. The car hooks up if I roll into the throttle and just hauls ass. If I hammer the pedal it lights them up and dances sideways. I usually shift at 5000 rpm as I still have the 5500 rev-limiter in it, no powers shifts are needed. I haven't come close to winding out 3rd or 4th yet - still learning the car and breaking in the motor (800 happy miles to date).

I can't imagine a shorter gear helping that much and highway cruising would suck.

Randy

Unique 289 FIA
Southern Automotive 396
Team III 16's
Brilliant Silver

[TurnpikeBoy]

Well, Brent, you can get 302 badges for the side...if you really want 'em. Car looks exceptionally clean without ANY badges, but, hey, whatever it takes.

Randy, you need to experience what shorter gearing does for ANY car - bang for the buck, this is untouchable when it comes to performance. Highway cruising in 5th. gear is no different than steep gears and a toploader. Powershifting is a holdover from old drag racing days :) but certainly not necessary...just fun. I think that stroker makes a tad more torque than the 302, no? - so I shift a bit more often than you need to. For me, a big part of the fun.

But - with the birth of 5 speeds, with selectable o/d ratios, there ain't no good reason whatsoever (except good tires, maybe..)to turn away from lower gearing. Got Torque? - great, use higher gears and a 4-speed. Got RPM? - you know which way to go.

Th only unhappy people out there are the ones without a Unique!
[:P];)

Yeehah

[TurnpikeBoy]

Well, Brent, you can get 302 badges for the side...if you really want 'em. Car looks exceptionally clean without ANY badges, but, hey, whatever it takes.

Randy, you need to experience what shorter gearing does for ANY car - bang for the buck, this is untouchable when it comes to performance. Highway cruising in 5th. gear is no different than steep gears and a toploader. Powershifting is a holdover from old drag racing days :) but certainly not necessary...just fun. I think that stroker makes a tad more torque than the 302, no? - so I shift a bit more often than you need to. For me, a big part of the fun.

But - with the birth of 5 speeds, with selectable o/d ratios, there ain't no good reason whatsoever (except good tires, maybe..)to turn away from lower gearing. Got Torque? - great, use higher gears and a 4-speed. Got RPM? - you know which way to go.

Th only unhappy people out there are the ones without a Unique!
[:P];)

Yeehah

[dmiller]

i'm not sure that i know what i'm talking about, but it seems that the advantage in a lower rear(larger number) end ratio is lost once one reaches the point that the available torque is sufficient to spin the rear tires. anything lower, making more torque available to the rear wheels is lost. if one then changes tires to wider, softer, slicks, etc. then one could justify a lower gear ratio. is my thinking correct?

my plan is to continue putting my car together, at this rate, i hope i have enough days left in my life to complete. i have a 289 fia with a 351 stroked to 408, using the 3.31 rear end with a tremec 5 speed.

[dmiller]

i'm not sure that i know what i'm talking about, but it seems that the advantage in a lower rear(larger number) end ratio is lost once one reaches the point that the available torque is sufficient to spin the rear tires. anything lower, making more torque available to the rear wheels is lost. if one then changes tires to wider, softer, slicks, etc. then one could justify a lower gear ratio. is my thinking correct?

my plan is to continue putting my car together, at this rate, i hope i have enough days left in my life to complete. i have a 289 fia with a 351 stroked to 408, using the 3.31 rear end with a tremec 5 speed.

[Brent]

My perspective on this is from an ex-drag racing point of view. Your right about about reaching the point of diminishing return on too much gear. In our S/Comp car we used a computer to monitor Rpm,driveshaft rev., tire rev front and rear, and G force, among other things. Sometimes a gear change felt great by the seat of the pants, but was actually slower in 330 ft and e.t. Everyone is correct about lower gears being cheap mechanical horsepower but as you stated when you can't put it to the ground whats the point? As light as these cars are I think letting the motor pull may actually produce better performance numbers than shifting every thirty feet.

But you know what they say about "opinions"

Brent

[Brent]

My perspective on this is from an ex-drag racing point of view. Your right about about reaching the point of diminishing return on too much gear. In our S/Comp car we used a computer to monitor Rpm,driveshaft rev., tire rev front and rear, and G force, among other things. Sometimes a gear change felt great by the seat of the pants, but was actually slower in 330 ft and e.t. Everyone is correct about lower gears being cheap mechanical horsepower but as you stated when you can't put it to the ground whats the point? As light as these cars are I think letting the motor pull may actually produce better performance numbers than shifting every thirty feet.

But you know what they say about "opinions"

Brent

[TurnpikeBoy]

<img src=images/icon_speech_yeah.gif border=0 width=29 height=15 alt=Insert Speech Icon: Yeah!>
DM, you got it right. The whole point in final drive gearing is a compromise - do you need acceleration or top end? If acceleration, go to higher-numerical ratio; if top end, go to lower-numerical ratio.

Of course, with higher-number ratios you get equivalent torque multiplication...which can lead to traction problems on typical street-type tires. Motor got big torque (i.e., over 425-450 ft-lb)numbers you really do not need higher-number gearing - install lower-number set and make the motor produce results. Your 408 most certainly doesn't need 4.09's, and 3.31's will work great. You'll have lots of oomph all over the scale, including top end.

I am partial to the 0-100 mph range, not too terribly bothered by giving something up above that range since noplace I can run that fast around here anyway. Track use would give reason for lower gearing but I'm not there yet - and I want to use this thing.

Besides, leaving damn near anything you find at the stoplight in the dust is just terribly viscerally satisfying. :D:D

Yeehah

[TurnpikeBoy]

<img src=images/icon_speech_yeah.gif border=0 width=29 height=15 alt=Insert Speech Icon: Yeah!>
DM, you got it right. The whole point in final drive gearing is a compromise - do you need acceleration or top end? If acceleration, go to higher-numerical ratio; if top end, go to lower-numerical ratio.

Of course, with higher-number ratios you get equivalent torque multiplication...which can lead to traction problems on typical street-type tires. Motor got big torque (i.e., over 425-450 ft-lb)numbers you really do not need higher-number gearing - install lower-number set and make the motor produce results. Your 408 most certainly doesn't need 4.09's, and 3.31's will work great. You'll have lots of oomph all over the scale, including top end.

I am partial to the 0-100 mph range, not too terribly bothered by giving something up above that range since noplace I can run that fast around here anyway. Track use would give reason for lower gearing but I'm not there yet - and I want to use this thing.

Besides, leaving damn near anything you find at the stoplight in the dust is just terribly viscerally satisfying. :D:D

Yeehah

[dmiller]

a lower rear end ratio would help my Honda S2000, it has no torque, launches are laff slow, but thinks do get quicker at 6000 rpm.
in first gear, one doesn't make any progress until passing 20 mph, which is about when the second cam lobes get switched on. then it has lots of acceleration.

however, a lower rear end would stress the already marginal clutch and tranny. honda didn't think those components thru very well.

[dmiller]

a lower rear end ratio would help my Honda S2000, it has no torque, launches are laff slow, but thinks do get quicker at 6000 rpm.
in first gear, one doesn't make any progress until passing 20 mph, which is about when the second cam lobes get switched on. then it has lots of acceleration.

however, a lower rear end would stress the already marginal clutch and tranny. honda didn't think those components thru very well.

[Okiesnake]

I just had the rear gear ratio changed from 3:31 to 3:71 and I'm glad I did! I have a 351W that puts out 400+HP and a Tremec 3550. The 3:71 feels like an adrenaline shot after the 3:31. In hindsight I think the 3:31 is too high for a SB.

[Okiesnake]

I just had the rear gear ratio changed from 3:31 to 3:71 and I'm glad I did! I have a 351W that puts out 400+HP and a Tremec 3550. The 3:71 feels like an adrenaline shot after the 3:31. In hindsight I think the 3:31 is too high for a SB.

[rdorman]

I don't know what come standard but I have a 3.75 with a wide ratio toploader. Driving the car back from Arizona, all 2000 miles. The motor (a Cleveland) is happiest above about 3500. At 80 MPH almost all the way back the engine was turning about 3800-3900 RPM. All the while returning 15.25 MPG (documented over 2000 miles). I now run a taller set of rears so it turns about 3500-3600 at 80. The low gears and wide ratio are certainly a kick in the pants but you better learn to shift quick!
Rick

[rdorman]

I don't know what come standard but I have a 3.75 with a wide ratio toploader. Driving the car back from Arizona, all 2000 miles. The motor (a Cleveland) is happiest above about 3500. At 80 MPH almost all the way back the engine was turning about 3800-3900 RPM. All the while returning 15.25 MPG (documented over 2000 miles). I now run a taller set of rears so it turns about 3500-3600 at 80. The low gears and wide ratio are certainly a kick in the pants but you better learn to shift quick!
Rick

[bluoval]

Someone said it depends on what your engine is tuned for, he's exactly right. A larger cubic in. engine will probably produce a lot of torque and require a lot less gear. A smaller engine will need more gear to help the lack of torque. Another consideration is overdive. You can get the Tremec trans. with two different overdrive gears. The standard is .68 and it's almost overkill, unless you have a big block or a 3.54 or 3.73 rear gear. The other option is the new Tremec 3550-2 or the TKO-2. These have roadrace gears. The gears themselves are stronger than the regular Tremec, and the syncronizers have been improved for better shifting and abuse from racing. The overdrive or fifth gear is .82. This keeps your RPMs up a little to help accelleration in top gear.

[bluoval]

Someone said it depends on what your engine is tuned for, he's exactly right. A larger cubic in. engine will probably produce a lot of torque and require a lot less gear. A smaller engine will need more gear to help the lack of torque. Another consideration is overdive. You can get the Tremec trans. with two different overdrive gears. The standard is .68 and it's almost overkill, unless you have a big block or a 3.54 or 3.73 rear gear. The other option is the new Tremec 3550-2 or the TKO-2. These have roadrace gears. The gears themselves are stronger than the regular Tremec, and the syncronizers have been improved for better shifting and abuse from racing. The overdrive or fifth gear is .82. This keeps your RPMs up a little to help accelleration in top gear.

[eliminator]

All I can say is with a 500 HP/500+ ft lbs of torque 427 FE a 3.31 gear works just fine. Will set you back in the seat through all the gears with a Toploader close ratio.

Eliminator

[eliminator]

All I can say is with a 500 HP/500+ ft lbs of torque 427 FE a 3.31 gear works just fine. Will set you back in the seat through all the gears with a Toploader close ratio.

Eliminator

[clayfoushee]

I'm sure it does depend on what engine you're running. I have a 427 side oiler with 500+ and I'd be scared with something more than a 3.31.

Unique 9929 427 side oiler

[clayfoushee]

I'm sure it does depend on what engine you're running. I have a 427 side oiler with 500+ and I'd be scared with something more than a 3.31.

Unique 9929 427 side oiler