Thanks GTOguy

I remember well being in the Navy at San Diego North Island. A buddy of mine came back to the barracks with a brand new 65 GTO. Wow what an awesome car.
Anyway next week I hope to get a date to drop off the Hemi/Vette and get started on the transmission swap, spring is coming.

 

Again, the stock TREMEC shifter location is in the middle of the transmission. You will have to modify the console to make it work. The vendors such as SST modify the shifters, as and example of the differences see below:


Stock TREMEC






Modified TREMEC:





In the For Sale section:

https://www.corvetteforum.com/forums...ec-tko600.html

 

If my lower torque 283 could move the car with the ring/pinion ratio and transmission I cited a higher torque will certainly do so; I assume the torque is relevant to establish peak shift points on a different engine....

If torque is a determinant then the people who like "the rule of 10" for the transmission selection must be wrong as that formula doesn't factor in torque... I don't pretend to be an expert in these matters - just stating what worked for me...

 

I also have a 1972 Porsche 911 that I've owned for 22 years. It has been my sports car of choice. I have 245,000 miles on it. I've driven it on over 8 different tracks (track days) on the West coast and down in the SE when I lived in Florida. I've rebuilt everything including the engine (1981 3.0L with twin plugs and webers). On a race track the key to speed is how the car pulls out of the corners. So when I rebuild this engine 14,000 miles ago I did two specific things. I built it to turn 8500 rpm like a race car. Then I had a cam cut that would lower the peak torque down to my shift points. Now when I come out of the corner I'm right on the torque peak and when I shift at the HP peak it drops right into the torque peak (245hp @ 6900 and 230 ft/lbs @ 4300, and the car only weighs 2200 lbs). This engine has been bullet proof and that's exactly what I wanted.

Now the Hemi doesn't make anything like the current engines when It comes to horsepower but 430 ft/lbs of torque at 2700 rpm is a lot. So that's what I'm going to be looking at with the TREMEC and possibly the 3.73 rearend.

 

The 'rule of 10', IMO is for a car that will be track driven. My '67 GTO comes in at 6.3 (2.56 x 2.48) with a stock 400 and a TH400 and does just fine (0ver 440 foot pounds of torque) and my '65 GTO does just fine with an 8.6 figure (3.36 x 2.56) with a 389 and a 4 speed with 440-ish foot pounds of torque. My '61 Corvette with a 383 stroker (375-ish foot pounds?) comes in at 11.5, (3.36 x 3.42), and first AND second gears are a blur. 1st gear is basically useless. So, personally, I ignore 'the rule of 10'. They even built tens of thousands of 6 cylinder Tempests with low-torque straight 6's with 2.56 gears with no worries back then. The 'rule of 10' makes great sense on a race track or a canyon road in a car with medium to low torque and higher HP (283, 302, 327 engines), but for a street driven car, it's not required at all, IMO.

 

Based on my specific experience I disagree. My 67 has a 3.36 axle and had a close ratio Muncie with the 2.20 1st gear - that’s 7.39 overall. It was a dog off the line even tho 1st was good to about 60/65 mph. Now I have the 3.27 1st gear in the Tremec - 10.89 overall. It’s very quick off the line; 1st is good to 45/50 mph. I normally shift at 30/35 mph when just cruising and when I do get on it the 1-2 shift drops in right at torque peak . What’s not to like? This set up works well for me! I guess I may have taken a tenth or two off my 0-60 time ...... oh gee!

 

I think it has to do with torque, and the kind of driving you do. A 327 with not a lot of low end torque would suffer with a 7.39 overall low in a performance situation. My '61 with the 383 has the same ratio in second gear with the trans I am running (second gear on my ST-10 is 2.20:1). I can start out in second briskly with no dogginess in sight with my 3.36 rear gear ratio. But I'm betting I have 80-100 more foot pounds of torque than a standard 327. High winding, high horsepower but lower torque engines need more gear to be responsive, but you knew that already. I suspect your '67 with the 3.36 axle would have pepped right up with a wide ratio transmission with the 2.52 first gear. Not a lot on paper, but on the pavement, big difference.

 

I believe you are correct! It’s strange that the car was ordered with the close ratio Muncie and 3.36 axle combo . That’s a lousy combo for a street car.

 

Well it gets more interesting everyday.

Talked to TREMEC distributor in Caldwell Id. Several guys in the shop where going to sit down and try to figure out how to do this. Then this afternoon I get a text message from them saying they can't do that with a Chrysler unless they custom build the bell housing for about $!200.

So I called the shop here who will do the install and they have a MOPAR guy. We talked and he pointed out another place that has an overdrive for my stock 833 Chysler Transmission.

One step forward and two back but then this is a unique car anyway.

 

Will there be enough room to fit an OD unit behind the transmission under the car body?

 

My buddy installed a Gear Vendors behind his 4 speed Hemi Box in a Challenger body. It looked to me like the Gear Vendor unit took up close to 20 inches of space, maybe a little less. The Vette has such a short driveline I am not sure there is room for a GV.

I can state the owner of GV had a late 90's Vette with an 4L60 4 speed Automatic and he installed a GV in his car. I never saw under the car but I watched it do acceleration tests. They thought with 8 speeds it would be quicker.
It actually ran a little quicker 1/4 mile without using the GV unit. The extra shifts took time away from acceleration. The GV overdrive unit was a .8 overdrive as I recall. The owner of GV wanted my buddy to have his Challenger tested for acceleration also but unfortunately on track day his clutch decided to go up in smoke so he was not able to participate but we watched everything. These GV units in the test had the push button control so you could floor it in 1st gear and when you hit red line hit the button and 1st gear now was .80 taller in overdrive. When you banged to 2nd gear you also hit the button which put you back into normal 2nd and so on. It functionally gave you an 8 speed. Which did not prove to be faster but the .80 overdrive was a nice option.
The very positive thing a about the GV units is they are really tough. Guys running over 1,000 HP engines did not break them. Same units are also used in Motorhomes. They work and are tough.
I think the availability of 5 and 6 speeds has really hurt the market for the GV units.
Mark

 

There is not, not in a C1 anyway; I looked at that closely before I went with a Tremec. The C1 driveshaft angles are severe enough and shortening them would just be problematic IMO...

 

This jogged my memory and I just verified it: from 1975 through 1987, Chrysler used an overdrive version of the 833 (also known as a New Process 440) in many of their cars and trucks for economy. It is a heavy duty unit with a 3.09 first gear and a .73 overdrive. It was made by reversing the 3-4 shift fork, using 1:1 fourth gear as the new 3rd gear, and the old third gear as the overdrive gear. This is great news, IMO....as you could source a good used unit for peanuts and it would be a direct bolt in, although you will need to verify the clutch plate input teeth. You won't have the super close ratios of a performance trans, but with your Hemi, you won't need them, either. Win-win, IMO....on the cheap.

 

FYI I just came back from my friendly local chrome shop and there was a custom truck chassis setting in one of the bays with a blown early hemi that had a TKO 600 attached to it. I will be back there Sat if you want more info. I'll try to get a pic of it, the look was awesome !

 

Pop Chevy
Yes any info is good at this point.

The guys from Modern Driveline in Idaho are still working on a solution so I've got my fingers crossed.

As long as I don't look at the stock market I'm ready to write a check, schhhhhhh!!!!!!!!!!!

 

So you are not going with the factory overdrive, bolt-in 833??

 

Well the stock market is killing me, I'm retired. So I'm going to wait on this upgrade. I did get a quote from TREMEC so it looks like it's a possible switch, just have to wait for now.

 

There's a rebuilt HD 833 4 speed overdrive on ebay right now for $950. Just sayin'.......

 

I have the same set up in my C3.. In retrospect I miss the 1st and 2nd ratios in my super T10 but love the overdrive. It makes highway driving a pleasure. I thought about the magnum but the additional cost and six gears was way more than I need. Depends on how you use the car. Silver sport was great to deal with and drop shipped the tranny to my installer avoiding the sales tax. Don't forget to buy a new shift lever like I did.

 

$4300 base price for this set up for a C2 owner worried about spending money VS a $950, bolt-in solution. Really??