Changing 5th gear ratio in a TKO

[Al G]

Is it possible to change the 5th gear ratio in a TKO-600? I've done all the research, played with gear ratio/speed calculators, considered my projected driving conditions and think I've made the right choice. But if I find out I was wrong, or circumstances change, can the 5th gear ratio be changed or is a new transmission required?

[Excaliber]

Curios, what OD gear do you currently have?

[terry251]

Al, see this thread for your answer (particularly page 2 from JB Cobra.)
.64 to .82 5th gear swap on tko600
Good Luck!
Terry

[Al G]

Terry,
Thanks for the link.

I'm going with .64 OD and 3.54 rear. Everyone has their own opinion on the best combination and may not agree with this one. I've ridden in a car with this combination with the same engine I'll be getting and it works fine for the type of driving I expect to be doing.

[wideglidejoe]

Just remember with your 3.54's and .64 OD, your final drive ratio will be 2.26. I'm sure you know that with all the calculators. With your FE, you'll have plenty of low and mid range torque, but the real question is, when you are cruising in 5th @ 60-65 mph, will you 1) be able to accel w/o pinging or down-shifting? and 2) is your cam the same as the one you rode in? Depending on how lopey/snotty your cam is, will it cruise in 5th w/o bucking? Your 5th cruise RPM is going to be really low at normal speed limits.

For all of the above discussions, I decided on .82 OD w/3.27's, for my 455 FE, for a 2.68 final ratio. For me personally, I'd rather live with a little more RPM's @ cruise speeds to make sure I stay out of 5th gear bucking, and be able to accelerate w/o downshifting to 4th.

I'm not trying to say you made a bad choice, just my opinion.

good luck!!
Joe

[Excaliber]

My engine, with the lumpy cam profile, bucks below 2,000 rpm. So, .82 for me with 3.31 rear gear. The cruise rpm is just about perfect for my engine at 70-75 with that combo (trans, rear gear, cam profile, carb, intake, timing, compression, etc.).

[elmariachi]

Originally Posted by wideglidejoe

but the real question is, when you are cruising in 5th @ 60-65 mph, will you 1) be able to accel w/o pinging or down-shifting? and 2) is your cam the same as the one you rode in? Depending on how lopey/snotty your cam is, will it cruise in 5th w/o bucking? Your 5th cruise RPM is going to be really low at normal speed limits.

I have a TKO600 with .64 5th gear behind my 427 FE with a 3.50 rear axle, which has a pretty aggressive cam but its not a wildly built engine. I too wrestled with this after building the car. A year later and 4k miles, I have no regrets. My setup has enough low-range grunt to cruise at 60 mph no sweat, but I rarely do because the package just feels better staying in forth under 70 mph. However, the rocket ride from 70 to 140 mph in 5th is better than any Six Flags ride.

[Forte's Minion]

But it is expensive! The output shaft is part of the swap. Both sides come to about $500.00 and the tranny needs to be almost completely disassembled to change
Steve