[tonyvol]

Hey guys, I've posted about this before but as I look back I wasn't real clear on the intended use of my car.

I'm trying to make a decision that I won't regret. I have a brand new TKO 600 .64 OD and I'm thinking about swapping it for a new TKO 600 .82 OD. I will most likely drive this car on side roads 45-65 mph) and stay off the main highway. This car won't be an every day driver...more of a toy.

I'm having Mark Jones build a 496 650 hp motor and and I was thinking that a TKO 600 .82 OD and a 3.55 rear gear would be a good combination. With a rear tire dia. of 26 in., the rpm calculator I ran says that at 66 mph I'll be turning 2500 rpm with the .82 OD. I believe the cam Mark uses isn't too radical. What should I do guys? TKO 600 .64 OD or .82 OD.

Thanks,
Tony

 

[CDN SS]

Without cam specs and peak torque rpm its just a educated guess but 2500rpm + should be fine when you get at or below 2000 then with a big cam it can be a prpblem 26" tires ???

 

[Lusox]

If your situation is as you said, 45-60 MPH with a 468 CI motor, then who gives a crap about the OD ratio? Don't spend a dime chasing something that won't matter. Fact is, you don't need a special tranny at all. If the driving conditions are as you describe, a plain old Muncie 4 speed and the motor would outlive you.
I drive an old Corvette with a ZZ430 and a Tremec 600 (.82 OD and 336 gears) but I drive 75-80 mph on trips of 1,000 miles to events, so to me it makes a difference.

Lusox

 

[tonyvol]

CDN SS, the cam will be a HR cam 238/248 @ 50 and 590/608 lift with a LSA 110. Mark said this motor will be based off of his 650 hp 496 but it will have brodix race rite heads. He said that the rpm range will be in the good range for a street car. It will probably top out around 6200 rpm.

Lusox, You make some valid points. One of the reasons I went with the TKO was because of the HP/TQ rating. I'm not saying that on occation I won't be driving 75 - 80 mph...I guess I was looking at 90% of my driving will be cruising back roads. That's why I was thinking of the .82 OD. I was thinking I would get more use out of the 5th gear. So I wanted to see what you guys thought, since you guys have pointed me in the right direction before.

 

[CDN SS]

CDN SS, the cam will be a HR cam 238/248 @ 50 and 590/608 lift with a LSA 110. Mark said this motor will be based off of his 650 hp 496 but it will have brodix race rite heads. He said that the rpm range will be in the good range for a street car. It will probably top out around 6200 rpm.

Then you will fine down to 2000 rpm ...... 3.55 rear with 26 tire is an odd combo if that never changes go the .82

 

[d1_bradley]

My '62 has same engine and TKO-600 with .82 OD. 3.36 rear gear, 28" tire. Would be much better with a 3.70 and that's what will go in when I bust the one that's there now. I do use OD when on the highway...... 70-75 is a nice cruise. Seems that as long as I keep it up around 2000 rpm or so its calm around town.

 

[tonyvol]

CDN SS, when you say "3.55 rear with 26 tire is an odd combo" are you saying that I would better going with a 3.73 rear gear or a different dia. tire? I'm planning on changing the rear gear anyways and don't have the tires yet.

d1_bradley, since your running basically the same combination...I ran a rpm calculator for a 3.73 rear gear, 26 dia. tire, and the .82 od and at 76 mph it will be turning 3000 rpm.

 

[CDN SS]

the nice thing about an OD trans is the ability to use a low rear gear for perf and use OD for cruising ..... Before you decide on a trans ratio decide on the tire height that fits your car / look etc you want and then gear for the type of perf you want then decide on your OD ratio .your motor / cam will cruise fine down to about 2 k maybe alittle lower

 

[d1_bradley]

d1_bradley, since your running basically the same combination...I ran a rpm calculator for a 3.73 rear gear, 26 dia. tire, and the .82 od and at 76 mph it will be turning 3000 rpm.

I ran the calc with my tire radius (14) 28" tires, 2300 rpm = 69.5 mph, and that's REAL close to what I see on the tach.

If I changed to a 3.70 gear (9" Ford), it would be at 2600 rpm at 71.4 mph. I could live with that and I think it would be MUCH more drivable in the lower gears.

 

[GRN69CHV]

Vince runs the .64 trans with 3.90 gears. Pretty sure if he had to do it again, he'd have went with the .82.

 

[hjdca]

I have the .64 OD TKO 600 with 3:73s and 275x50x17 tires... I have the comp cam 292h cam, so, a lot of overlap... At 80 mph, the tach is at 2100 rpm... I drive alot of fwy, and 5th gear is too low at 50, with my big cam, I'm at around 1600 rpm, that is too low... I usually shift out of overdrive around 50 mph... I drive the fwy around 75 mph, so, the .64 is good for me, but, if I could do it over, I would put 4:11's in the rear and keep the .64 od... Sounds like for what you want, the .82 od would be better than the .64...

 

[CDN SS]

FYI I started with a TKO with .64 od 3.73 and 28" tires ...... my engine /cam wont cruise clean below 2200 .... switched to a .82 with 4.30 rear same 28 tire ......... Perfect for my car ........but its really not a freeway flyer .......cruise at 2400

 

[70 SS 454]

i think a higher rear ratio and the .64 would be great... performance down low and nice cruise rpms on the highway

i just got your PM so call me anytime

 

[tonyvol]

GRN69CHV, Thanks for the reply. I talked to Vince on Friday and he said the same thing...that he would probably go .82 OD if he had to do it over again.

hjdca, what size cam do you have?

CDN SS, how is first gear with the 4.30 rear gear. Is it too short?

 

[71454Chevelle]

I solved this overdrive selection dilemma by bypassing the TKO and going right to the T56 Magnum. :yes: I haven't got it installed yet but hopefully in a couple of months.

I know its abit more expensive than the TKO, but I was able to purchase one from Summit when they had their 15% discount a few months back. Got it for a little under $2400. :hurray:

Its the best of both worlds, 5th gear is .80 for back road driving and 6th gear is .63 for highway cruising. On top of that, the gear spreads are (IMO) for desirable than the TKO and its rated 100ft/lbs stronger. Just food for thought.

 

[CDN SS]

GRN69CHV, Thanks for the reply. I talked to Vince on Friday and he said the same thing...that he would probably go .82 OD if he had to do it over again.

hjdca, what size cam do you have?

CDN SS, how is first gear with the 4.30 rear gear. Is it too short?

1st gear too low? .......fine for the way I use my car .....but may not be for everyone if a DD etc ....... no right or wrong answer really depends on what you ulitimatley decide on tire height and rear gear and how much and what speed you drive on hwy .. with your motor I would not cruise much below 2k

 

[hjdca]

GRN69CHV, Thanks for the reply. I talked to Vince on Friday and he said the same thing...that he would probably go .82 OD if he had to do it over again.

hjdca, what size cam do you have?

CDN SS, how is first gear with the 4.30 rear gear. Is it too short?

Comp Cam 292h, dur. at .006 is 292, 292; dur. at .050 is 244,244; lobe separation 110

I also have a wideband and have my carburator dialed in very well... I still do not like cruising on the fwy below 1700 rpm... It is a little too much for my cam... I like cruising at 1900 - 2000 rpm... I am about 70, 75 mph at that rpm... 50 mph feels like it is lugging a little when you go up a slope..