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Transmission options...

2K views 8 replies 6 participants last post by  Arvin 
#1 ·
Hey guys...new here. Just doing a lot of research before I order my kit. So you may see me asking more than a few silly questions. I apologize in advance. =)

I have decided to go with a fe big block. The intention is to source an old 390 and build it up, possible bored and stroked to a bit larger displacement, only around 375 to 400hp, balanced and blueprinted to be as bulletproof as possible. The car will be driven a lot, mainly city fun driving, but also some highway. With that said, what manual transmission options are there for fe big blocks? ...and what donor mustangs could they be sourced from? Thank you in advance for your time.
 
#2 ·
No donor trans from a Mustang FOX BODY would be a good choice.. a tko 500 or 600 or a top loader would be the only way to go.
Fortes is in my opinion the best place to go for one stop shopping. Do a package deal with him . It ain't cheap. FE means Freeking Expensive.
Do plenty of home work on a FE build... it ain't that straight forward like a 302 or 351 is.
 
#4 ·
the 500 has a 3.27 first gear and the 600 has a 2.87 first gear. Big difference

Your rear ratio will play into the equation. And tire size.

Go to one of the many gear ratio calculator and check the rpm at cruise speed etc.

You cam choice will be the determining factor of where you motor can cruise at hiway speed.

Best of luck.
 
#5 ·
Mike at Forte's Parts Connection has all the parts and info you need as well as competitive prices. I bought a lot of parts from him. I am running a TKO600 with an FE427 and 3.55 ratio IRS. If I were to do it all over, I would not get the .64 overdrive though. I don't like the big RPM drop between 4th and 5th. Instead I would get the .82 overdrive and 3.27 rear end ratio. that would also give a better 1st gear and make the 4-5 shift more like the 3-4 shift.
Just my opinion.
Wayne
 
#8 · (Edited)
Keep in mind that 5th gear is usually intended to be a highway cruising gear, not a high performance gear. Some overdrive gears don't have the same strength as the others. With that in mind, plan your rear end ratio with the 1.0 final drive and appropriate tire diameter.

My car has a nearly identical 1.0 final drive ratio with a .7 overdrive. I use a 3.5 gear ratio, even with large 30.5" diameter tires. That produces an engine rpm of 1970 at 75 mph, in overdrive. In theory, it would run about 155 mph with the engine near redline with the 1.0 ratio. Whether the car could actually do that, depends a lot on wind resistance. With smaller diameter tires, I would have chosen a little taller gear, around 3.25.

If you've got a big cam that produces low power at that type of rpm, then lower gears might be needed.

With modern Corvettes, capable of 180-205 mph, the top speed is not achieved with the tallest gear ratio available - it's only there for good gas mileage when cruising on the highway.

One thing I like about new multiport EFI engines - you can't beat the gas mileage. My 430hp LS3 gets 20 mpg in city driving and should get significantly more when highway driving. The new LT1 455 hp is rated 16/28, but I get 20 mpg in city driving with it, too.
 
#9 ·
I have a 351W bored and stroked to a 408 with FAST EFI and a TKO600 that was dynode at 512 hp and 534 ft-lb torque, solid rear with 3.55 gears. I have the rev limiter set at 6500 rpm on both the FAST EFI computer and the MSD Ignition 6AL. I have 315-35ZR17 rear tires. With these numbers, the calculator shows that in fourth gear (1.0 ratio) my top speed is 140 mph (I know that to be close) and in fifth gear (.68 ratio) top speed is 206 mph (don't know that one). I also know that it likes to cruise best around 85 mph (2700 calculated and actual). No power in fifth gear though - need to downshift if you need to pass at 80 mph to fourth. I don't go any higher than 4th unless cruising on the interstate. Don't worry about fuel economy because I get at best 9 mpg anyway.
 
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