Like miles says above, the car want really designed for higher speeds, but it's definitely capable of them. I assure you they can go faster than what you think.
The only reason it wouldn't be able to its if it's not running well. Check your timing, give it a tune up or at least new spark plugs. Check and change your fuel filters.
And about the swap, the 3 speed auto is all mechanically operated, while the 4 speed had electronic components and that is why it would be more work to install. The 5 speed are just like your 3 auto in that they too are all mechanical.
If you want to do the swap because you just want to, by all means do so, if it's just because of the reasons you mentioned above, the transmission isn't really your problem. For one or more reasons your car isn't producing the power it should be if you can't go over 75. Especially downhill.
I did the math, in third gear (1.00) with the stock 3.9 diff, and 21 inch outside diameter tires gives 72 mph at 4500 rpm. I'd have to get it up to 6K+ rpm to hit 100 or slap some 30 inch tires.....
From what I've read I just have to swap the thrust disk for a fly wheel + clutch, change out the pedal box, and hook up the clutch cable? I think you need to snip a wire going to the ECU as well.
You think with this being a FWD I could just pull the tranny out the back without pulling the motor? Only FWD transmission I've ever pulled was on a 86 Honda.
Edited by Ionstorm66, 23 August 2013 - 07:05 PM.