Transmission Advice

[66vette]

I am considering a transmission upgrade from my current four speed to either a 5 or 6 speed. My 66 has the original 327 engine 300 hp build up to approximately 350 hp. I am running 4.11 rear gears. Keisler is recommending their RS 400 transmission, Hurst Driveline is recommending their TKO 600 since I am running 4.11. Hurst is recommending their TKO 500 only if I was running 3.04 or 3.36 gears. There is quite a price difference between the Keisler and Hurst. I have asked for a quote from Tremec but they have ignored my request for the last two weeks. What recommendations does this forum have based on those that have upgraded to either of these transmissions? I appreciate your input to allow me to make the correct decision.

 

[LLC5]

I am considering a transmission upgrade from my current four speed to either a 5 or 6 speed. My 66 has the original 327 engine 300 hp build up to approximately 350 hp. I am running 4.11 rear gears. Keisler is recommending their RS 400 transmission, Hurst Driveline is recommending their TKO 600 since I am running 4.11. Hurst is recommending their TKO 500 only if I was running 3.04 or 3.36 gears. There is quite a price difference between the Keisler and Hurst. I have asked for a quote from Tremec but they have ignored my request for the last two weeks. What recommendations does this forum have based on those that have upgraded to either of these transmissions? I appreciate your input to allow me to make the correct decision.

With 4:11 rear gears I would definitley want the 6 speed. Hurst gave you accurate advice, the lower engine speeds will absolutely help drivetrain durability. Good luck with either choice.

 

[66vette]

Hurst is also offering their TKO 600 in either the .64 or .82 for the same price, which one would be better? I believe the .64 would provide lower cruising RPM.

 

[LLC5]

Hurst is also offering their TKO 600 in either the .64 or .82 for the same price, which one would be better? I believe the .64 would provide lower cruising RPM.

The .64 with a 5 speed transmission might have too big of a big gap between 4th and 5th gears so the .82 might be a better choice for that transmission, but with a 6 speed transmission I would go with the .64 as you stated, for the lower cruising rpm and maximizing the benefit of the 6 gear ratios. My C5 6 speed manual has a .50 6th gear and it is a great package. After driving it for 7+ years I am not sure that I would want to go back to a 5 speed in any vehicle if I were given a choice. Good luck deciding.

 

[66vette]

Both the TKO 500 and 600 are 5 speeds, I did not have them quote 6 speeds.

 

[orlandjoe]

I did the swap from a Muncie M21 to the TKO 500 in 2004 and I am very pleased with the result. I have a 3.55 rear gear, 454 cu. in. engine and use an 11 inch clutch. My rpm is about 2300 in 5th gear at 70 mph and I get 14 miles per gallon at that speed. Works for me. Car is very driveable now on the interstates. Bought from Keisler and had no problems with them at all. Had to get a different speedo gear from them for the trans to correct the MPH. No charge for the extra speedo gear and they mailed it out pronto.

 

[66vette]

My concern with the Keisler RS400 or 500 is first gear 3.37, I believe it will be like a granny gear and will not be usable.

 

[71hcc]

My concern with the Keisler RS400 or 500 is first gear 3.37, I believe it will be like a granny gear and will not be usable.

You are right. With a 4:11 gear and a 3:37 first gear you will end up with a rear ratio of around 5:14. I put a TKO 500 with a 3:37 first in my Chevelle that had 4:11 gears. It made it a pain to drive, you just get the car moving and you have to shift. I changed the rear gear to a 3:42. If you don't want to change your rear gears I would use a trans that has the 2:87 first gear. As far as the gap between 4th and 5th, it's not a problem because 5th is your cruising gear. What I mean is, your usually not power shifting into fifth, even though I have it works fine. If I had it do do over again I would have went with the 2:87 first instead of the 3:37.

 

[orlandjoe]

I agree with 71hcc, the tall 1st gear gives my 3.55 a feel like 4.56 off the line. I do shift half-way through the intersection or so it seems. I still think it's well worth having the 5th gear available for cruising. Get the 2.xx 1st gear if you are not changing rear gears.