Thinking about a TKO 500 from Keisler
Thread Starter
Pro
Joined: May 2008
Posts: 582
Likes: 9
Thinking about a TKO 500 from Keisler
I will soon have to start driving my 79 Vette to work as a daily driver. This is going to be around 30 miles one way on the interstate so I was thinking about swapping my Richmond T-10 for a TKO-500 from Keisler. Wondering on what other people have experienced with there fuel mileage and reliability with this transmission?
Currently I have a 3.55 gear and at 55 MPH average 19 mpg but at 70 it drops to 15 mpg and 75 it is around 14 mpg. Speed and mileage is verified with GPS.
I am hoping to get over 20 mpg at 70 with the overdrive. Any thoughts or ideas?
Currently I have a 3.55 gear and at 55 MPH average 19 mpg but at 70 it drops to 15 mpg and 75 it is around 14 mpg. Speed and mileage is verified with GPS.
I am hoping to get over 20 mpg at 70 with the overdrive. Any thoughts or ideas?
Racer
Joined: Dec 2009
Posts: 415
Likes: 10
From: Richmond Va
Just do a search on gas mileage or plug in TKO and you will get more than you wish for as far as information. Keisler and a few other sites have a rpm calculator too that shows the drop in rpms w/ various combinations. Apparently, the wait is the issue.
Burning Brakes
Joined: Apr 2007
Posts: 1,039
Likes: 62
From: Kona Hawaii
Use 10:1 rule on first gear.Ex:rear gear 3.55 X 2.87 first gear TKO600 =10.1 ideal for takeoffs. rear gear 3.55 X 3.27 first gear TKO500 =11.6 not ideal,first gear will be very short kinda like a granny gear. On the OD you have two choices with the TKO600 an .64 which will give 70mph at 2000rpm with 255//60/15 tires.The other ratio .82 will give 55mph at 2000rpm with the same size tires.
Judging by your post looks like the .64 OD ratio would work better for you.I use a .76 OD ratio with my 3.08 rear gears so I can use OD at a lower speed and not lug my engine.I'm averaging just about 20mpg going 65mph with my set up...Good luck with your build...Aloha's
Judging by your post looks like the .64 OD ratio would work better for you.I use a .76 OD ratio with my 3.08 rear gears so I can use OD at a lower speed and not lug my engine.I'm averaging just about 20mpg going 65mph with my set up...Good luck with your build...Aloha's
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Le Mans Master
Joined: Sep 2004
Posts: 5,116
Likes: 5
From: Livonia MI
Have a friend with a 79' L-82 4 speed 3.70 axle car, that did the Keisler TKO 500 conversion. He doesn't drive the car often, so probably not paying much attention to fuel milage. Have ridden in the car on the highway at 70 mph, and a pretty nice rpm drop from 1.00 4th to 0.68 od 5th. While not 100% sure, think about 3300-3400 rpm in 4th, dropping to about 2300 rpm in 5th. If interested, PM me some contact info, and I'll get you guys in touch. Mark
Pro
Joined: Apr 2009
Posts: 650
Likes: 1
Hiya,
I'm running the TKO500 with a 3:70 diff and the first gear is quick, but not too bad. Well I'm not running it RIGHT now because I broke an inner axle, but BEFORE it broke 1st gear was useable. I had a 383 and it had pretty good low end torque.
Good Luck!
I'm running the TKO500 with a 3:70 diff and the first gear is quick, but not too bad. Well I'm not running it RIGHT now because I broke an inner axle, but BEFORE it broke 1st gear was useable. I had a 383 and it had pretty good low end torque.
Good Luck!
Le Mans Master
Joined: Dec 2009
Posts: 6,397
Likes: 649
From: Saskatoon Saskatchewan
I asked KeislerJeff if that would be the case with the RS400 3.37 first and my 3.70 rear end of if I should get an RS600, he said he drove a Corvette with the 3.70 rear and 3.37 first and didn't think it was too steep.
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Le Mans Master
Joined: Dec 2009
Posts: 6,397
Likes: 649
From: Saskatoon Saskatchewan
I've heard several people on this forum give that 10 to 1 rule of thumb but I'm skeptical as to its utility. I know the best rearend gear for drag racing can vary considerably from car to car depending on weight, horsepower and rpm where peak horsepower is produced meaning for some cars a 3.00 to 1 rear gear is best and for other's it might be a 6.50 to 1. I don't see any way this 10 to 1 rule of thumb can be applied indiscriminately to all Corvettes.
Racer
Joined: Mar 2005
Posts: 294
Likes: 1
From: Racine Wisconsin
TKO500 with 3.36 works great
When I was considering which overdrive transmission to go with I did some math. The street racers like the 4.11 rear axle with their M20 (i.e. first gear total ratio 10.3:1 or with the M21 9.04:1). I have a 3.36 rear axle behind a M20 (i.e. first gear ratio 8.46:1). I considered the TKO600 with 9.64:1 and the TKO500 10.9:1. Both acceptable and better than the either the Muncie (8.46:1) or the Richmond (11.18:1). I selected the TKO500 and it seems to be just right for my style of driving.
Pro
Joined: Mar 2000
Posts: 669
Likes: 80
From: NE USA
I run the TKO500 with a 3.55 rear gear. Over the years I have had several chevy trucks with manual trans and granny 1st gears. I have never considered the Vette to behave like those old trucks where you would rarely use 1st gear.
I would agree it is steep, (and pretty damn fun!) other than problems hooking it pulls real hard. For just cruzing around town it is very easy to drive. As for the OD ratio, a 383 carberated engine with a street performance cam will need more RPM's at the typical 60 to 80 mph highway speeds to be real useful. I would think this would be true for most carbed engines.
I have no idea what my fuel milage is at highway speed, I will say the difference of having the OD gear is amazing runnin 80 down the interstate. The car is very long legged.
I would agree it is steep, (and pretty damn fun!) other than problems hooking it pulls real hard. For just cruzing around town it is very easy to drive. As for the OD ratio, a 383 carberated engine with a street performance cam will need more RPM's at the typical 60 to 80 mph highway speeds to be real useful. I would think this would be true for most carbed engines.
I have no idea what my fuel milage is at highway speed, I will say the difference of having the OD gear is amazing runnin 80 down the interstate. The car is very long legged.
Race Director
Joined: Jan 2000
Posts: 12,399
Likes: 247
From: San Jose CA
Granny firsts in most trucks are 4.5x:1 or higher. My F250 had a 6.32:1 first which was good for getting loads moving or walking up inclines. Typically 2nd in a truck is nearly equivalent(if not a bit lower) to first in a V8 passenger car.
Pro
Joined: Nov 2003
Posts: 692
Likes: 1
From: Peabody Ma.
Any way to confirm what I have?
Racer
Joined: Mar 2005
Posts: 294
Likes: 1
From: Racine Wisconsin
Since you don't have the car yet you can't inspect underneath (i.e. rotations of driveshaft for a single rotation of axel.
If the tach and spedo work correctly you could have someone check the RPM at a particular speed in high gear (1:1) and calculate the ratio using the formula,
MPH = (Tire Dia (inches) x RPM) / (axle ratio * 336)
For example with a 27" tire and 3.55 axle an RPM of 2000 corresponds to 45 MPH in high gear.
You will like it.
If the tach and spedo work correctly you could have someone check the RPM at a particular speed in high gear (1:1) and calculate the ratio using the formula,
MPH = (Tire Dia (inches) x RPM) / (axle ratio * 336)
For example with a 27" tire and 3.55 axle an RPM of 2000 corresponds to 45 MPH in high gear.
You will like it.
Pro
Joined: Jan 2006
Posts: 526
Likes: 1
From: Millington TN
I'm running .355's with a TKO-600. 70MPH puts me just above 2000rpm. And first gear(according to Keislers calculator) behaves like a 4.04 now. I don't really get into fifth until about 50mph. So in town I don't really see the benefits but definitely on the HWY mileage goes up.
Instructor
Joined: Sep 2009
Posts: 201
Likes: 2
From: Ocean County NJ
I've got 3.55 rear with the RS500. As some have said, first gear is pretty short compared to all of the other manuals I've driven, but I do not have experience driving anything older than an 89 S10 pickup.
I don't have all the numbers yet but RPMs at 80mph are much lower than the TH350! Overall I enjoy it.
Andy
I don't have all the numbers yet but RPMs at 80mph are much lower than the TH350! Overall I enjoy it.
Andy
