.82 or .64 TKO?

[Flash68]

Hey guys. I have to send back my TKO 600 to get the shifter location changed, so I have the opportunity to switch to the road race version with the .82 overdrive/5th gear. Wondering if I should do it. Here is my setup and welcome comments and suggestions.

68 Camaro
Currie 9" rear with 3.70 gears
TKO 600
Procharged 406 small block = 650-700rwhp
Air Bar 4 link
275 front/335 rear tires

Intended use: 95% street driving, maybe some road course or 1/4 mile for fun occasionally

Thoughts?

[Josh69]

Have you driven it yet as is to see what it behaves like in OD?

I have the TKO600 with the .64 and a 3.73 in a Moser 12 bolt with 25.5" tires. I would have gone with either the .82 or a 3.90/4.11 if I had it to do over. I'm around 1900rpms, and it wants to load up. I'm running a single plane and a quick fuel 750 race carb built for E85. I'm looking to supercharge mine as well, and have some of the same concerns. I imagine it'd be worse with the blower drag on it in my situation. I'm heading to the dyno room to try to sort it out. If not, I'll be dropping in some 4:11's.

My cam is a hydraulic flat tappet 236/242 @ .050, 108cl, .516/523 lift. I guess it really comes down to how your motor wants to run under load at 2K rpm's or less. Right now you'll be in the 1800-2000 range at 55-60. Fourth gear can be pretty annoying with a 3:70 at 60mph if you can't hit 5th. I drive 30 miles each way to my office on a 2 lane where it's hard to get past 60mph.....it sucks not using the OD in those situations.

[mazspeed]

.64. I wish I had a .50 in mine with a 3.73 gear set.

[Flash68]

Have you driven it yet as is to see what it behaves like in OD?

I have the TKO600 with the .64 and a 3.73 in a Moser 12 bolt with 25.5" tires. I would have gone with either the .82 or a 3.90/4.11 if I had it to do over. I'm around 1900rpms, and it wants to load up. I'm running a single plane and a quick fuel 750 race carb built for E85. I'm looking to supercharge mine as well, and have some of the same concerns. I imagine it'd be worse with the blower drag on it in my situation. I'm heading to the dyno room to try to sort it out. If not, I'll be dropping in some 4:11's.

My cam is a hydraulic flat tappet 236/242 @ .050, 108cl, .516/523 lift. I guess it really comes down to how your motor wants to run under load at 2K rpm's or less. Right now you'll be in the 1800-2000 range at 55-60. Fourth gear can be pretty annoying with a 3:70 at 60mph if you can't hit 5th. I drive 30 miles each way to my office on a 2 lane where it's hard to get past 60mph.....it sucks not using the OD in those situations.

Car is not done so no I have not driven it yet. I shouldn't have loading up problems at low rpms since I have EFI. I failed to mention that I guess.

[Flash68]

.64. I wish I had a .50 in mine with a 3.73 gear set.

Really? Why do u wish for .50? U like to cruise at 95mph on 280 or something? :D

[MtotheIKEo]

if it's going to be mostly a street car/cruiser I would go with a .64

[Blown353]

I shouldn't have loading up problems at low rpms since I have EFI. I failed to mention that I guess.

Depends on the cam-- regardless of induction some cams just aren't happy being loaded under a certain RPM and the engine will surge and buck no matter what combination of timing and AFR you give it.

With 3.70 gears and that tire diameter, my preference to make it a freeway-friendly car would be the .64 gears unless the cam is really big. But knowing you have Don's old motor the .64 OD should be just fine, I seem to remember that cam "cleaning up" around 1600-1700 rpm from the few times I was in the car, so you should be able to shift into 5th around 50-55 mph and it will be happy.

Why are you having to send the TKO back to move the shifter? You can easily switch the shifter location yourself between the 16.25 and 19" location; you just unbolt it and rotate it 180. The only more complex shifter relocations are if you have the shifter located really forward under one of the midlength covers instead of on the tailhousing, that gets more involved and needs extra parts.

[Flash68]

Depends on the cam-- regardless of induction some cams just aren't happy being loaded under a certain RPM and the engine will surge and buck no matter what combination of timing and AFR you give it.

Makes sense. I don't think is cam is really huge based on what I know.


With 3.70 gears and that tire diameter, my preference to make it a freeway-friendly car would be the .64 gears unless the cam is really big. But knowing you have Don's old motor the .64 OD should be just fine, I seem to remember that cam "cleaning up" around 1600-1700 rpm from the few times I was in the car, so you should be able to shift into 5th around 50-55 mph and it will be happy.

That's a pretty low rpm so yeah that should be okay.

Why are you having to send the TKO back to move the shifter? You can easily switch the shifter location yourself between the 16.25 and 19" location; you just unbolt it and rotate it 180. The only more complex shifter relocations are if you have the shifter located really forward under one of the midlength covers instead of on the tailhousing, that gets more involved and needs extra parts.

I am sending it back to Keisler cuz they have to modify the tailshaft or some part that apparently only they should do. I asked them it is more work than just switching that plate around. This will also allow me to run the Pro 5.0 shifter base that I want to run now, which I cannot in the tranny's current form. It's pretty cheap actually and they are just gonna switch this tranny out for a new unmodified one from Tremec where they have not messed with it yet except for the 19.25" shifter location (currently it is 16" - so, a 3.25" difference).

[mazspeed]

Really? Why do u wish for .50? U like to cruise at 95mph on 280 or something? :D


I'm going a lot faster, trust me :lol:
You really do want the .64. It's a bigger jump from the 4th gear, but well worth it on the freeway. You won't be sorry.

[Flash68]

I'm going a lot faster, trust me :lol:
You really do want the .64. It's a bigger jump from the 4th gear, but well worth it on the freeway. You won't be sorry.

I believe it. And I hope to join you soon! :P

Yeah I think the .64 is the one to stick with.

[The WidowMaker]

i went with the .82 version, but i have a 28.5" tire in the rear and 3.73's. i debated it for a while, but i determined that freeways around here are too slow to worry about cruising at 90. the .82 was perfect for a 75 mph cruise.

how tall is that 335? i think there is only one size 335, but i wasnt sure.

Tim

[Flash68]

i went with the .82 version, but i have a 28.5" tire in the rear and 3.73's. i debated it for a while, but i determined that freeways around here are too slow to worry about cruising at 90. the .82 was perfect for a 75 mph cruise.

how tall is that 335? i think there is only one size 335, but i wasnt sure.

Tim

My 335 is 26.06" tall, so quite a bit shorter than yours.

And I have no problem cruising over 100+ in my area. ;)

Yeah I am pretty set on going with the .64 now.

[ChevyThunder]

Really? Why do u wish for .50? U like to cruise at 95mph on 280 or something? :D

All the time , and then some :)

[Flash68]

All the time , and then some :)

Yeah, I figure I will be doing some high speeds in my Camaro, but the REALLY high speeds will be seen in my 996TT. :D

[bobhamilton15090]

I would go .64 that is what I did in my mustang w/ 3.73 gears and I run 2k rpm at 80 mph and 3k rpm at 100

[Flash68]

I would go .64 that is what I did in my mustang w/ 3.73 gears and I run 2k rpm at 80 mph and 3k rpm at 100

Wow, I like those numbers. How tall is your rear tire Bob?

[Blown353]

I would go .64 that is what I did in my mustang w/ 3.73 gears and I run 2k rpm at 80 mph and 3k rpm at 100

Wow, I like those numbers. How tall is your rear tire Bob?

In order to spin 2K engine RPM at 80mph with 3.73 gears and a .64:1 OD, that requires a 32" tall tire.

However, with that same combination 100mph would be 2510rpm, so something doesn't add up.

[bobhamilton15090]

im running a 275/40/17 rear tire, my od gear is actually .63, but thats close enough to the topic for me!

[Blown353]

im running a 275/40/17 rear tire, my od gear is actually .63, but thats close enough to the topic for me!

Bob, a 275/40/17 tire is 25.7" diameter when new; so with your 3.73 rear gears and a .63:1 OD ratio (and also assuming there is no slip anywhere, and there shouldn't be with a stick) your RPM/MPH is as follows:

RPM / Speed
7000 RPM 228 MPH
6500 RPM 212 MPH
6000 RPM 195 MPH
5500 RPM 179 MPH
5000 RPM 163 MPH
4500 RPM 146 MPH
4000 RPM 130 MPH
3500 RPM 114 MPH
3000 RPM 97 MPH
2500 RPM 81 MPH
2000 RPM 65 MPH
1500 RPM 49 MPH
1000 RPM 33 MPH

So your 3000 rpm @ 100 mph observation is very close, but at 2K rpm you're going 65.

[Flash68]

Bob, a 275/40/17 tire is 25.7" diameter when new; so with your 3.73 rear gears and a .63:1 OD ratio (and also assuming there is no slip anywhere, and there shouldn't be with a stick) your RPM/MPH is as follows:

RPM / Speed
7000 RPM 228 MPH
6500 RPM 212 MPH
6000 RPM 195 MPH
5500 RPM 179 MPH
5000 RPM 163 MPH
4500 RPM 146 MPH
4000 RPM 130 MPH
3500 RPM 114 MPH
3000 RPM 97 MPH
2500 RPM 81 MPH
2000 RPM 65 MPH
1500 RPM 49 MPH
1000 RPM 33 MPH

So your 3000 rpm @ 100 mph observation is very close, but at 2K rpm you're going 65.

I look forward to hitting 7000rpm in 5th gear. :lol:

[Vegas69]

Thread should have ended at 95% street car.:D

[Flash68]

Thread should have ended at 95% street car.:D

yeah yeah yeah... :willy:

[Blown353]

I look forward to hitting 7000rpm in 5th gear. :lol:

LOL... it was a copy/paste from a spreadsheet. :lol:

[Flash68]

LOL... it was a copy/paste from a spreadsheet. :lol:

I hear ya. And thanks for posting it!

[bobhamilton15090]

So your 3000 rpm @ 100 mph observation is very close, but at 2K rpm you're going 65.

You can tell I drive at 100mph more than I drive at 65mph let alone 80mph

Did I mention speed limit is 55mph?

[sikryd]

I have the same type of question...
I have a 67 Camaro with an iron headed big block, tire is a 275/60/15 for now, and I have 4.10 gears. From looking at speed calculators, it seems that with the .64 unit, I will be doing 73 MPH @ 2300 RPM. With the .82 unit, I will be doing 57 MPH @ 2300 RPM.
I live in Hawaii, and traffic is sh!t on oahu, plus freeways are not very long. So I'm wondering if I should get the .64 or .82... Jeff at Keisler said I should get the .64, but I'm really wondering if that is the correct choice. My cam in the 468 is pretty big, 290/625 108 solid roller, have a single plain intake, and motor is built to go higher RPM. When I built the motor, we had a 1/4 mile track here, but no more.

[The WidowMaker]

if you are buying the overdrive because it has one, make sure you can use it. figure out what your cruising speed will be and then make sure your rpm is high enough for that cam.