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I just converted my 64 383 powered roadster to a 5 speed, a great addition for highway driving.
I felt that the 6 speed in my c6 was kind of redundant, I would use 5th or 6th but really not both
EDIT: I just looked at you profile and see you have a 350 engine but unknown h.p. If you would have added you signature to your post I would have known this.
My 1957 383 car has a 1961 T-10 with what ever 1st gear ratio is in that? No problems taking off on a hill for me but my 57 only weighs 2850 lbs. What engine do you have in your car?
Tires are 215/65R16.
Engine is Ram Jet 350, 350 HP, 400 ft.lbs. Good low end torque
I have a 6 speed in my 67, I need to be going at least 80 before I can use it. It was already in my car when I bought it as a project but if I was going to change a 4 speed out, a 5 speed is perfect.
I have my 6 speed purely for performance potential. At around 6500 rpms with street tire OD and can sustain that, I am at 175 mph roughly. Slowing down in top gear, at 80 mph I am about 600 rpms out of the cam. I am inside my cam range in 5th gear at 80mph, any slower I fall out of the cam range again. If I want to drive leisurely on the freeway with pedal potential, I pull it down to 4th a 1.24 ratio thru a 3.70 and I cruise the speed limit.
My ROD gears are 3.04, 2.22, 1.57, 1.24, 1.00, special .80 (actually called a road race gear).
My rev limiter is set at 8200rpms.
Last edited by TCracingCA; 10-08-2021 at 12:32 PM.
I have my 6 speed purely for performance potential. At around 6500 rpms with street tire OD and can sustain that, I am at 175 mph roughly. Slowing down in top gear, at 80 mph I am about 600 rpms out of the cam. I am inside my cam range in 5th gear at 80mph, any slower I fall out of the cam range again. If I want to drive leisurely on the freeway with pedal potential, I pull it down to 4th a 1.24 ratio thru a 3.70 and I cruise the speed limit.
My ROD gears are 3.04, 2.22, 1.57, 1.24, 1.00, special .80 (actually called a road race gear).
My rev limiter is set at 8200rpms.
Good info for people that track their cars but I would be surprised if any other posters in this thread are tracking their cars. Most are looking to reduce rpms at freeway speeds to reduce engine wear, engine noise and for better gas mileage.
My C6 has 3.42:1 rear versus a 3.36 in my 67. Sixth gear is 0.5 OD. I have to be going near 80mph in 6th for the engine to have any throttle response at all, and my 67 engine is way weaker.
That little chart showing above my ROD Owners manual was just an accident, getting into the picture. I was looking up my ROD gearing, and sat the Manual on top to picture the manual.
But I had installed a 3.36 planning on a potential 200mph Silver State Classic Nevada run, to rich of a dream for my budget. Those were ratios for that.
Here is that handwritten chart just in case someone is trying to see what I did.
At the time of doing this, could find 15 inch diameter tires in Z ratings anymore. I had one new set left in a 25.67 diameter. In the modern I will be running Michelin TB-5s rated 168mph. Thus recalibrating to new top speeds, dropping the 200 mile death wish.
Last edited by TCracingCA; 10-10-2021 at 12:55 AM.
I considered a 6 speed for my 65 but went with the TKO 5 speed when I discovered that you have to trim the fiberglass dash below the radio to make it fit. .
3:70 gears and I cruise at 75 at about 2100 RPM. I get 22 mpg on the highway. Very happy with my decision.
There are a few different 6 speeds out there. In my 85 , I have a Richmond that 5th is 1 to1 and 6 is .62 overdrive with a 383 and 3.70 rear.
I have a 5 speed in my 71, approx., 400 hp, 400 tq. Its a .6 overdrive in 5th. I cruise at 2000 at 80. I get 25 mpg highway.
Silver Sport shows a variety if overdrive ratios. If you motor is low tq then go with a .76 overdrive.
I find the 5 speed more useful on the street and usually just drive it like a 4 speed until I hit the highway. I put a 6 speed in a friends Camaro , 5 and 6 are overdrive , and find the extra gear and work is not worth it for street use.
If the RPM are too low at Cruising speed the gas mileage will suck as the engine is lugging. Also there will be no throttle response.
As a guess I would want to be at 1400 to 1500 at 60 mph,
The GM LT1 7th is .5 its very tall. I cant use it unless Im really flying...now it does have large cam but still.
Steady state cruising is all its good for at "get a $$ ticket speed". .8 is much better
Dont regret it but if I had to do it over a 5 spd would be perfect. Back in those days they didnt have Z06 gearsets to put in...too much $ for me at the last time I had the trans cracked open.
The Tremec 6 speed is a modern transmission and has a short throw between gears, one of the best shifting manual transmissions around. No one has mentioned shift feel, as well the Tremec can be shifted quickly at high rpm's and can handle more torque than most most LS engines make.
I have a 65 coupe with a six speed Richmond. It is a 427 with a 4:11 rear. it cruises very nicely in 6th. I find it offsets the rear gears well. Had a 6spd in my 04 Z06 and liked that immensely. Hated that I sold it.
Also have a 2018 with an A8 and that seems really fine. I use the paddle shifters to keep from becoming bored.
10-08-2021, 01:35 AM
