What is the best cruising RPM ?? I need a good rear ratio and tranny!

[smoknbarrels]

Hi, I have some problems with tranny and rear selection..
I have been trying to cut corners and determine a tranny that will hold up to my moderate perf 454, it has lots of cam and I will be going with a standard tranny..
I have been looking at Tremec 6 speeds, all the gears are great ratios until the 6th.. it is 0.50. so with my 29 inch tall tires I will only be doing 1500 RPM at 65 MPH. This is far to low isn't it?? I know corvettes run at 1300 RPM on the hiway(same tranny), but this can't be done with my carburated engine can it? people say I need my engine at a minimium of 2000 RPM.

I really would like an overdrive but I don't know of any other popular affordable Trannys that will hold up to 500lbs of torque..? muncies are great, but they lack an over drive, I don't want to drive down the hiway doing 3300 RPM.
I wanted a Tremec TKO-600 but they are too much (would have been perfect).


Have any ideas!??

[cooters]

i dont know what you have for a motor combo, a 454 with an rv style cam would be awesome at 2000rpm.

[smoknbarrels]

My 454 has ported heads, intake, headers, with a few other goodies, but the big thing affecting my RPM would be my cam , which is 292 adv. duration and 550 valve lift. so it is much larger then an RV cam. its power band is about 2500-6500 RPM.
I don't nessisarily think that I need to be cruising in that range do I?

would it run good under 2000 RPM on the hiway? perhaps someone has tried this before...

[RACINJASON22]

here are some #'s for ya. Hope they will help. I'm not real sure about the bigblock stuff cam seems a little big just the #'s
Ratio = (rpm x tire diameter) divided by (mph x 336)

RPM = (mph x gear ratio x 336) divided by (tire diameter)

MPH = (rpm x tire diameter) divided by (gear ratio x 336)

Tire Diameter = (mph x gear ratio x 336) divided by (rpm)

[smoknbarrels]

yea, i have been using some good online calculators, but I just don't know what would be a good RPM to run my big block with on the hiway..?
Does anyone know of a good strong manual tranny that has good ratios?

I can get my hands on a cheap Borg Warner super T-10, if I have to go to a 4 speed (is it as strong as a muncie?) but then I also go to a 3.08 ratio rear end.

[cooters]

you should be in the power range while cruising. Depending what you are doing, a new process 4500 is ok, or a T5

[71Chevy4-speed]

http://www.richmondgear.com/01sixspeed.html

5th is 1:1
6th is overdrive.

[smoknbarrels]

that looks good, you can even pick all your ratios.. also looks expensive.. i think i looked at these richmond 6 gears before.. but they were in the $3000 range.. which is unfortunately a little out of my range. since they are not common i would have to buy it new..
I have been looking at the T-56 that LS-1's use.. its a 6 speed.. all gears are good but 6th is too low of ratio, so I was thinking of just only driving with 5 gears. since those trannys are popular and cheap.

perhaps call 6th gear a "police interceptor passing gear" since I would be doing 230 MPH @ 5000 RPM with my set up. LOL..! sounds like a waste thou.

[Longhorn Man]

a T 5 can't hold up to a strong 305, there's a reason GM never bolted them to a 350... ever.
Are you racing your big block, or just want a kick ass strong motor?
You should have enough torque to not need real deep gears. A normal old 4 speed stick, or a Th400 if you are sick of shifting, would be idea with a 3.07 gear. You'll cruise at 2500 or so.

[1968SWBBigBlock]

Hey longhorn - are you on 315 doing 90mph? That could be to slow

[Longhorn Man]

west side on I 270 north bound, had it at 100 for a mile or so, had to lift for the exit to I 70 west.


I can't remember where the first photo was taken, that's when the old GMC rolled 500,000 miles.

[67ChevyRedneck]

If you really want OD, why not a tremec 5 speed and a 3.73 rear end? That should give you what you want, right?

[smoknbarrels]

I will be running about 470 HP in my 454 (Flywheel HP) so i have been trying to find a decent manual tranny that will hold. I also want to determine what RPM is good to cruise at, (being I have lots of cam).

sounds crazy but i am trying to get the best of both worlds, I want it to be a tough street machine, but also have an over drive gear so it will see pleanty of use on the hiway.

[Longhorn Man]

If I'm not mistaken, the tremec 5 speed is not an overdrive.
2000 - 2500 RPM is what I would say you should shoot for.
Any idea on what kinda torque numbers this engine will pull? If it has a bunch of torque down low, then a low gear would be wasted. The caddy motors make so much low end power that you can run real low gears, like a high 2.something, and it'll still pull like crazy from the lights, yes loaf along at 2000 RPM in a one to one final gear. With a tall gear, there is no need for an overdrive, and you indicated cost being an issue... there are no low cost overdrives that'll handle your engine... not for a long peroid of time anyways.