kzibjj

I have a 1972 LT-1, which I love. Only problem is it has 4.11 gears in the rear, which I knew when buying it. Only thing missing is a 5th gear and a cup holder...lol. Acceleration is great. Highway mileage, not so good...lol. Being new to the Vette world, do they make a 5 Speed tranny for this car? That way, I still have the acceleration and better highway mileage. Or would it make better sense to swap rear end gears? Thank you.

Bikespace

I'm assuming you already have 4 speeds with your LT-1? Good choice!

There are numerous threads here for 5-speed conversions (Tremec TKO-600 or similar), and even 6-speed (T56), and several companies that bundle complete solutions. Search on those parts to find some inspiration.

My 80 4-speed came with 3.08 gears (Still VERY quick with the wide ratio ST-10), and at some point a PO put 3.08s in my 79 auto. The latter is less quick, but fine on the highway.

c3_dk

The 4.11 is not the "problem", the "problem" is, you need a 5th gear.
Install that, and you will love your 4.11 gears.

Find a nice T5WC transmission !

ddawson

Questions to ask yourself. Will I be reducing the value of a real LT1 with a five speed swap?
Do you not care and would rather enjoy the car during your time with it?

Then does the rear end need rebuilding anytime soon. Yokes are in good shape and not worn down?

With a 4 speed 1:1 At 70MPH right now your turning 3580 RPM.
With a 5 speed 1:82 your now at 2936 which is about what a 3.36 rear end gear turns.
Now if you get the TKO with a .64 5th gear your at 2291 RPM which would work well.

I'd go 5 speed myself.

Barry's70LT1

I have 3:70 gears, I installed a TKO-600 over 10 years ago. Best thing I ever did.
I know a 5-speed is an expensive option, however if you plan on keeping the LT-1, you'll never regret spending the money.
Best of both worlds, enjoy the performance of the 4:11's and the overdrive for cruising.
https://shiftsst.com/

Gordonm

5 speed all the way. I have done a dozen of these conversions. Nobody has ever regretted doing this. I liked the 5 speed so much in my car I went with a 6 speed. Its a weekend job. I have it down now from a 4 speed to 5 speed in about 10 hours.

kzibjj

Thank you everyone for the responses. Existing rear and yokes seem to be fine. I do plan on keeping it for a while. Sounds like a 5 or 6 speed is the way to go. I'll look into this. I'll keep the existing, matching numbers 4 speed on the side.

C3 4ME

If I had your car and the funds to do it, there wouldn't even be a post here. I'd have installed the 5 speed already. I wouldn't consider changing out the 4.11 gears. Also, the 5 speed conversion kits are completely reversible, so it would be a no brainer to me.

C3w4sp

Installed a tremic tko 500 in my 75 back in 2005. Can't believe it was that long ago, so don't recall the specific gear ratios. But homework is necessary. You must consider the entire gear set ratios in the tranny and compliment the gearset to the rear gear ratio. First gear ratio and the splits are as important as the o.d. gear ratio. My rear gear is 3:55 and at 80 mph the rpm is about 2,400.

With your 4:11 rear gear, a very low 1st gear ratio could behave like a granny gear in an old truck. The first gear ratio of my tko with my 3:55 is the equilvalant to having a rear gear ratio of something like a 4:40 + -. It would be worthless with a 4:11. And yes, it will light the tires, hit red line, grab second, and I haven't crossed the street. It's stupid fun.

Also, because my stroker motor is carbed and has a moderate cam, I stayed away from 6sp trannys and bigger (smaller #'s)o.d. ratios in 5sp`s. Unlike today's fuel delivery systems my setup likes a little rpm. At highway speed anything less than 2,000 rpm causes it to lug a bit. With a carb the tip in throttle response at low rpms at highway speed will suck.

Mako72

Installed a Keisler TKO-600 (.64 OD) kit years ago. Besides the 383 stroker, absolutely the best thing I have done to the car. I can run with late model vettes on the interstate.

PainfullySlow

If you decide not to go with a 5 speed, depending on where you are located I may have a 3.08 rear that I would be willing to trade for your 4.11.

kzibjj

I will keep that in mind. I see you're in Tolland, Ct. I'm in Danbury, Ct....pretty close to each other.

Crimson Thunder

Just be aware of the first gear ratio of your new 5 speed. You want to achieve a 10:1 first gear ratio with your 4.11 gears.

A TKO 500 with its 3.27 first gear will be 13.43 which will drive you crazy shifting into second 30 ft after leaving a red light.

A TKO 600 will be better (but not ideal) with its 2.87 first gear giving you 11.79.

FYI your M21 gave you a weak 9.04.

kzibjj

Maybe this is a dumb question, but would I even bother using first gear with a TKO 500? Would it be practical to start out in second?

PainfullySlow

Wow, that is close! Very cool!

Anyway, my recommendation would be with the others: install a 5 or 6 speed manual. If that is either cost or time prohibitive and a rear swap makes more sense, my offer still stands.

zwede

I don't know where that "10:1 1st gear ratio" came from. I've heard it for years and in my opinion it's completely bogus.

I have the Tremec TKO with 3.27 1st gear. I used to have 3.08 rear gears. 1st gear ratio 3.27 * 3.08 = 10.07:1. Should be perfect, right? I hated it. It was way to tall and I had to slip the clutch all the time at low speeds.

Swapped the 3.08s for 3.73s. 1st is 3.27*3.73 = 12.2:1. I love it now. Actually all the gears work much better and I'm not in between 3rd and 4th at city speed (45-50 mph) any longer. Now it's always in 4th until I need to stop at a light. I can also go to 5th at 55mph rather than 65.

EarlyC34me

It comes from drag racing and preferred launch ratio off the line not street setup

GregX1

Did you ever consider adding an overdrive?
Just asking, as nobody in talking about it.

I did drive a C3, with a ZZ454 engine, a 3-speen auto, + OD, and the OD was a fine 4th gear.

I don't know if anybody is using an OD behind a manual transmission, and not sure it would fit, but it could be an option

69ttop502

Well back in the day, Motion used to put Hone overdrive units in some of their C3 builds. Don’t know if those are still around.

derekderek

You are looking at 2 ratios. Overall in high gear, and your launch ratio. That is total ratio between crankshaft and rear wheels in 1st gear. 9:1 is good for a street car. 10:1 if you are actually launching. If too high a 1st gear with a high numerical rear, you will be shifting into second in 2 car lengths.