Wat Rear Gears Are You Running???

[MAXVELO]

I have 2:73 and I would like to change to something a little more light to light friendly. my first gear wraps out to about 60+ mph. I would like something a little more "FLASH" friendly (0-60). I dont really run on the highway much but If I do I would rather not be hitting 6 grand @ 60MPH. Im still kidking around installing a 5 speed with maybe 3:31 or so to get the best of both worlds. Whats your Guys suggestions on this?
Thanks Gary

[klayfish]

Yikes!! For that motor you have, I think I'd be hesitant to go much above the low 3's. I have 3.73s in my 351W w/about 400hp and it'll light up the first few gears in a hurry. That much power could get scary with the wrong set of gears.

Steve

[rdorman]

I agree. Lots of motor there. Torque multiplication not really needed! But that aside........ I would go to the low 3's. If you have a close ratio box perhaps going to a wide ratio box would be the ticket. With that much torque and intended use a wide ratio box would be my first choice.
Rick

[John McMahon]

2:88's in a Jag IRS with a Richmond Gear 5 speed (not overdrive model).

[lewismc]

I'm running a 3.73 with a Richmond 5 speed. My motor runs around 3800 rpms at 65mph. Personally I wouldn't go with a gear any taller than 3.50. If you're really worried about turning high rpms at highway speeds, get a transmission with an overdrive gear.

Lew

[clayfoushee]

I'm running 3.31 in my 427 SO, Jag-rear, 4-sp toploader, and find that set-up about perfect....just the right balance for a big block w/ that kind of HP. First gear is usable, and it's around 3K in 4th at 65mph.

[HighPlainsDrifter]

Hi,
I'm running a 3.25 possi in a 9" Ford. Good for all round use.
I don't have overdrive and would like your 2.70 gears for freeway cruising, the noise is deafening. I have 1/2 your power and can lyte the tires at will, seriously - you need to keep your gears and put a throttle stop on at 1/2 throttle on the street. Too scary !
Perry.
Gary; There is no street available manual transmission that will handle your torque, a built C-6 like you have will.

[BB427]

C.R. Toploader
3.54 posi
26.5" tall tire

Brent

[Zoom This]

So, I'm thinking that whatever gear ratio you choose should have very little to do with street/highway driving, but more with what rpm the motor needs to pull in top gear through the lights. If you make max horsepower at 6500 rpm, then do the math for tire diameter, tranny ratio and what the car "likes" through the 1/4 mile....2 gears, three gears, 4 gears? If I was racing your car I sure would feel more comfortable using an automatic or manual hydraulic shifter.

By the way, my 418 runs the standard 3.73 gears with a Tremec 5 speed with .68 overdrive. Like others, I find first gear useless unless you're caught in heavy stop and go traffic for a period. Still don't like the 3.27 tranny first gear ratio however since both me and my motor don't like stop and go heavy traffic. If I were to do it over I'd get the TKO II and a 3.27, 8.8 rear.

[MAXVELO]

Appreciate the info Gents. I really hate to pull this tranny out. It has a reverse pattern valve body for the shifter and a shift kit and I love it! What do you guys think of an OD tranny for it with 3:31's?
Reason Im even considering it is I had some clown in a WS6 Trans am start revving his engine next to me at the light. I would normally have ignered him but he was obviously determined and he was gonna do it even if I didnt! (his Girl was in the car) We took of and he jumped me on the light. When he shifted into 2nd gear he was about 1 1/2 car lengths on me. I was about half way through first gear but about that time I het my power band and pulled on him. ( wheres a camera when you need one? You shoulda seen his face when I blew by him!) Any how at the next light hes Girl said "WOW, THATS A FAST CAR!" And he proceded to get mad at her for talking to me. anyhow most of these runs are from light to light. and Im not geared for it.

[Widowmaker]

I'm running a 3.54 posi rear gear with a 393 inch engine and a Tremec TKO and a 0.68 fifth gear. My 70 mph rpms are around 1800 in fifth gear which is rarely used on the two lane mountain roads of western North Carolina. Fourth gear (1.00:1.00) works just fine there.

[maxrpm]

I have two diff. ham setups for my 9" rear. 3.50locker & 4.11 spool. I swapped the 4.11s in a year ago and won't even think of putting the 3.5s back in. With 28" tall rear tires & a heavily modified wcT-5 5spd I run thru the mph trap at approx 119mph at 6-6200rpm in 4th gear. On the street 60mph equates to about 2300rpm in 5th gear. It can still motivate top end. Once...just once I watched the 160mph speedo run out of sweep at approximately 6300rpms in 5th gear. Although I miss my big block in there I knew it would disintegrate the T-5 and my alternatives were the automatic or a HD 4-spd.
Someone stop me...I've been contemplating putting the 429C-6 w/transbrake, halo & 14x32s back in.

[maxrpm]

Maxvelo, I don't know what tire height you run but after giving it some thought I bet keeping the C-6(can't believe I said that), adding 3.50-3.73s and some good biting dragrace oriented rear street tires would be phenominal on the street in your car...never wear slippers to a footrace.

[Tom Wells]

Uh Gary,

Something just doesn't seem clear here

I have less HP than your sig says you have. I use 315/35-17 Pilot rear tires, with a C6 and a 2.88 axle. I can blow the tires away at any speed, up to and over 100 mph in a 3,000 lb car that has 50-50 weight distribution.

If I want to go, I put the gearshift in drive and modulate the tire spin with my right foot

I also have a 2200 rpm stall converter that I think really helps the overall performance. What are you using?

What kinda tires you got? Is the car tubbed and running 16" wide wrinklewall slicks or what?

Just curious,

Tom

[RallySnake]

Max,

What's the problem? You won, right? I'd leave it alone until you break something. When you HAVE to repair it, you upgrade!

If you must get out of the hole first, get a torque converter with a higher stall speed and a line lock brake setup. Very few people are going to out shift your C6 in a drag race. With a little practice, you can learn to hold the car with the brake as you gradually bring the revs up, watch the cross light, when it goes yellow, count to 6, release the brake and punch it. If there is no left turn light (oops!), you'll win!

You could step up to a 3.31 rear end but you'll be revving that big motor to death on the freeway. Gas station stops will be more frequent, too.

My small block works pretty good through the Tremec 5 speed and the Jag 3.31 rear. It's fine for rallies and the overdrive is great for freeway crusing. It's OK for autocrosses, too, just leave it in second. It shifts kinda slow in a drag race situation though.

Have fun and I hope you see that bozo again,
Paul

[exrodder]

2.73's and 2100 at 65. Pro streeted Model A sedan i had with 4.56's and it about drove me crazy when I was on an open road. Running 65 in that car on interstate was not much fun but it sure had some git up and go. Nicer to cruise in cobra with the airplane gears though.


exrodder

[John Poling]

Loaded question, you really need to select a ratio based on the power curve of your engine, the diameter of your rear tires and the final gear (non-overdrive) of your specific transmission. Basically you need to be at your intended cruise RPM and the lower end of your power curve at that RPM. For a typical street use car I have always figured a cruise RPM of around 3000 in your final "NON-O.D." gear. I used to own a 1970 Buick G.S. Stage 1 4-speed, it was a 462ci big block with an M-22 behind it and a 3.64:1 rear gear, cruise RPM in 4th was right at the 3000 RPM point and this was the factory set up.
Now my Cobra is not the large ci variant but I would think that the theory is the same. Keep in mind also that you are not trying to move the mass that a typical big block application would need to. My thought is to error on the conservative side and go with a little lower (numerically) gear maybe a 3.55:1 instead of the 4.56:1.

My current set up is a mild 351W with a C6 (2100 stall) and a 3.55 gear with 315/35/17" tires in the rear which equates to about a 25.75" tall tire. My cruise RPM is just under 3000 RPM at 60 MPH. My drive train was originally built by John York to a 350HP range and pretty much anytime I want a thrilling ride feel it's there with this set up. My basic power curve is from about 1600RPM to 5800RPM.

John

[maxrpm]

I do agree with you John. Gearing selection should be based on what your driving intentions are. Back in the good old days I had a big-block 4-spd car that I ran around town in that I installed 5.67 gears because I did alot of light to light streetracing. That was FUN! Ahhh, wasted youth! I'm gonna go reminisce.....

[Michael C Henry]

427 sideoiler+.030,Ford toploader,P255 ZR 50/16 BFG ,Jag 356

[MAXVELO]

I have the opportunity to purchase a set of 3:15 gears. Just curious what my RPMs would be @60 or 70 mph? My rear tires are P315/35ZR17's. Thanks Gary