External Gear Reduction

[Christ]

Originally Posted by cRiPpLe_rOoStEr

Compact-wise, nowadays a Subaru dual-range 5-speed stickshift is an interesting option.

Problem being they dont like to operate without equal loads on all 4 outputs.

Also, if using a gearbox, only the gears with a ratio value higher than 1:1 would be of use. The rest would be splitting the existing ratios without providing much in the line of help, instead adding extra driven mass and friction/fluid shear. Consider something like a T5 gearbox with all but 4/5 removed. I believe both are OD gears.

[cRiPpLe_rOoStEr]

Some months ago a friend of mine was considering to buy a 1st-gen Kia Sportage, and we were debating about the possibility to adapt an electrically-activated overdrive unit. We've considered the one out of some old Aisin transaxle used in the 7th-gen Corolla, with a .76 overdrive ratio, which would get the rear-end ratio of the MT version close to the AT version without any permanent compromise to drag times or uphill driving.

[RiderofBikes]

Originally Posted by Christ

Also, if using a gearbox, only the gears with a ratio value higher than 1:1 would be of use. The rest would be splitting the existing ratios without providing much in the line of help, instead adding extra driven mass and friction/fluid shear. Consider something like a T5 gearbox with all but 4/5 removed. I believe both are OD gears.

Your pretty much right on it, a Chart found The T5 Transmission Swap Thread
Provides a Key to the ratios.

The vehicle in question:
1352-247.....09................(1995) Firebird V6 3.4L

Ratios: 3.76.....2.18.....1.42.....1.....0.72, 3.73 rear end
This is also a Non-WC Tranny.

What i was thinking of, is using no higher than 4th, and basically having a (0.50:1, or 0.60:1) external reduction case.

Even then, there still might be a chance to use 5th+(0.72:1) External Reduction Case

Gear Ratio Calculator allows me to play around with options, and find the best matching RPM's/speed, compare Stock to added Reduction Case side by side...

5th(0.72) Stock.......................................2164rp m.....65mph
5th (0.72) + Reduction case(0.72)...........1558rpm.....65mph
T56 swap
6th (0.50) ...............................................150 3rpm.....65mph
respectively

Effectively all you'd be doing is adding that 2nd OD gear without doing any sorta swap/internal change. Only thing would be is you wouldn't be dissabling it at anytime unless you swapped out shafts and removed the case. But giving the fact its only a work daily driver without any planned mods to performance or handling i don't think there would be an issue. chugging along around 55-60mph might produce some interesting results

EDIT:
Example:
The straight shaft would be best, and the actual Gears for the external case can be found in other T5 parts piles for ease and cut cost on the gears themselves., All that would need to be done is have a Case CNC'd by your local College for the WIN!
The other two offset shafts would require the axle to be flipped for the wheels to rotate the correct way....

[metromizer]

If you were experimenting with a rear wheel drive, solid rear axle car, you could fit it with what is called a 'quick change' rear end. Real common in dirt track racing, a 'quick change' allows the pit crew to change rear end final drive ratios in about 10 minutes. The teams carry several set of inexpensive quick change spur gears in the trailer, to accommodate different sized/configured tracks.

For FE experiments, there is no reason a guy couldn't pick up a used quick change rear end and some sets of gears at a roundy-rounder swap meet for $500. New gear sets are only $70/set retail, there are at least 60, count 'em 60 different ratio available!

Once the fab work of outfitting the car for the new rearend housing, shock mounts, spring perches, whatever, gear changes become a snap.

http://www.youtube.com/watch?v=Xw1CZoyfrb0