TKO 600 BBC Which gear?

[jeff198901]

I have a 66 biscayne with a 510hp 427 big block chevy. I am currently running some 3.73 gears in the car but I feel like i need some more gear. My car has an operating rpm range of 2200-5800rpm. These gears were fine for my old motor with a much less aggressive cam. If i go into 5th gear now(.64OD) the car starts to lug.

Has anyone run a 4.30 gear with this transmission and a big block chevy?

Thanks!

[andrewb70]

I have a 66 biscayne with a 510hp 427 big block chevy. I am currently running some 3.73 gears in the car but I feel like i need some more gear. My car has an operating rpm range of 2200-5800rpm. These gears were fine for my old motor with a much less aggressive cam. If i go into 5th gear now(.64OD) the car starts to lug.

Has anyone run a 4.30 gear with this transmission and a big block chevy?

Thanks!

I guess I would want to know the tire size and what kind of speed you like to maintain on the highway. With a big block and 4.30 gears, I would think 1st gear would be useless. The lugging at lower RPM could also be a tuning issue.

Andrew

[jeff198901]

I guess I would want to know the tire size and what kind of speed you like to maintain on the highway. With a big block and 4.30 gears, I would think 1st gear would be useless. The lugging at lower RPM could also be a tuning issue.

Andrew

I guess I should've included that! It is a 28" tire. 275/60/15. The car just came back from a reputable shop. It goes like crazy. Desired RPM is 60-65mph for cruising in 5th. (if possible)

it runs 1-4 just fine. Just likes to lug in 5th

[ilikeike]

I run the RR TKO with the .82 5th. Mine doesn’t like to cruise below 1800rpm or so. It bucks a bit due to the lumpy cam if go much lower than that on the rpm.

[andrewb70]

I guess I should've included that! It is a 28" tire. 275/60/15. The car just came back from a reputable shop. It goes like crazy. Desired RPM is 60-65mph for cruising in 5th. (if possible)

it runs 1-4 just fine. Just likes to lug in 5th

If you went with 4.11 gears, that would put you just over 2050rpm@65mph and at about 2360@75mph...

If you went with 4.33 gears, that would put you just over 2160rpm@65mph and at about 2500@75mph...

Andrew

[Lonnies Performance]

4.30's are pretty steep for a car that peaks around 6000 rpm.

Find the minimum RPM the car is currently happy with in 5th, & work your way backwards to calculate the gearing/minimum speed you can comfortably use 5th.

I would think a 4.10 is getting pretty close to max for the 1-4 gear ratio combination.

[jeff198901]

my OD is .64

I took some notes today while out in the car.

50mph is 2500rpm in 4th
60mph is 2800rpm in 4th
70mph is 3300rpm in 4th


75mph is 2200rpm in 5th

Trans Ratios: 2.87, 1.89, 1.28, 1.00, .64

[Lonnies Performance]

With a 2.87 low, I would not want much more gear, making 1st very short.

Unfortunately the OD ratios suck in this trans.
.64 is too much & .82 is not enough for many vehicles... a .75 would be nice. (hope someone is listening)

I would love one of these in my Camaro instead of the Muncie with 4.10's.
I have a similar problem with a large solid roller cam that is not happy under 2500.

For approx $500 in parts, you can get the .82 OD main shaft & gear set for your trans.
This knocks your 3.73's down to a 3.06 whereas your current final gear ratio is a 2.39.
Unfortunately, this only takes your 70 mph, 3300 rpm cruise down to 2700, which is still pretty high, but you can still cruise in OD at 50 turning approx 2000 rpm.

Your current 1st gear is deep with a 3.73, similar to a T56 Magnum with 4.00's (2.66 1st), but it has .8 5th & .63 6th for more OD choices.
I'm currently building a pickup with 4.10's & the T-56 Magnum, hoping it gives me the best combination across the board.

[slammed68]

Are you running an aggressive cam? I have a mild 468, 3.55 gears, 25.6 tire. With the .64 overdrive I run 5th gear down to 50 mph or so.

[jeff198901]

Are you running an aggressive cam? I have a mild 468, 3.55 gears, 25.6 tire. With the .64 overdrive I run 5th gear down to 50 mph or so.

ItÂ’s a muthr thumpr cam. The car goes like crazy 1-4. Just likes to lug in 5th. If IÂ’m going 75 in 5th it seems to feel okay!

My old motor which had a much smaller cam would cruise all day at 50mph in 5th.

[andrewb70]

ItÂ’s a muthr thumpr cam. The car goes like crazy 1-4. Just likes to lug in 5th. If IÂ’m going 75 in 5th it seems to feel okay!

My old motor which had a much smaller cam would cruise all day at 50mph in 5th.

Is this carbureted or EFI?

[jeff198901]

Is this carbureted or EFI?

carb