well i havnt been here in a few years but im back for now...
my gta needs a new trans, i can get one with this spec list for 1500cad give or take:

Master Overhaul Kit, High Energy 3-4 Frictions, High Energy Extra Wide Band, Brand New "Lazer Straight" 2-4 Brake Drum, Unbrakeable Sun Gear Shell, .500 Boost Valve, .378 Lo/Rev Boost Valve to increase Line Pressure in Manual 1st and 2nd Gear, Corvette Servo Piston, B&M Street & Strip Shift Kit, Teflon Pump Bushing, Filter, a 1-2 super servo, rebuilt heavy duty stock TC.

im mechanically inclined but know next to nothing about transmissions. i know all that stuff is essentially what i want in a trans. if im doing it once do it right.

is there a taller fourth gear i can use to keeps the rpms lower at highway speeds?

thanks for the help! reading everything on this forum again is making me regret not driving my baby.

 

The only aftermarket gears that I am aware of change first and second gear. Pretty sure you are stuck with 1:1 for third and .70 for fourth gear.

 

Your easiest upgrade to get a lower final drive ratio would be to swap your 3.73 rear end out for a 10-bolt 3.42/3.23/3.08 or 2.73. Or got 9-bolt equals of 3.45/3.27(what i have & have hit 21mpg from my TPI/350/700R4)/3.08 or 2.72.

Depends on how much off-the-line "grunt" you are willing to sacrifice to get highway mpg. If you are mainly a city driver.....Go too low & it could be worse mpg because of the engine having to work harder during constant stop & go.

 

Or grab you a http://www.gearvendors.com/index.html unit, slap one on & get Double Overdrive out of it, but those aren't real cheap, especially for a car that is barely driven.

 

that .37whatever int/rev valve is a lil big. i'd probably only go .3 max, normally a .296 with the corvette servo is enough to break the tires loose on a manual 1-2 upshift with the plate drilled to b&m specs and their spacers at the 1-2 accumulator installed. honestly i only really like a .3 and larger valve for 200 4-r's. while the separator plate is off you could block 4th accumulator with an extra checkball into the case at the channel hole into the piston/tap it in and stake it in a lil. that will firm up 4th a lil but hardly noticeable. as a bonus it will increase your band life on the fourth gear shift.

 

oh man i didn't see you listed the servo twice. a super servo is great, so is a corvette and it's a lot cheaper. the super servo gives 90% versus the 60% corvette. the vette is rated over 600hp and with the wide band it will be snappy enough.