[400TT]

My brother runs a Tremec 3550 in the black Harrison. Was running with only 230rwhp, but has been putting 330rwhp through it for last 6 months.

The car is circuit raced every few weeks or so. The car is drag raced monthly/bi-monthly. And street driven.

3550 has been rebuilt once and will require rebuilding every couple of years or earlier for this sort of use/abuse.

Personally I think the T5 is a better shifting box, smaller, lighter, quieter, less power loss...but with 3550 you would never have to worry as much about the abuse you give it. Anything stronger would be overkill unless your thinking some serious forced induction. T5's are normally rated around 300ft, where as 3550 is 425ft. Just make sure you get world series T5.

T5 is much smaller and would be an easier fit. Not familiar with the G-Force, but shifter location will be fine. Tail shaft will be fine. The only problem you will have is clearance in the tunnel for rear part of the gearbox housing. We had to remove the strengthening ribs to get enough clearance in Harrison, but we moved the engine back a lot further than usual. I seriously doubt it's going to be a problem.

Here are the ratios:

TR-3550 3.27 1.97 1.34 1.00 0.68
(.68 5th makes for a perfect cruise gear, not useful for track use).

3550 was designed as a replacement for T5's, so ratio's are comparable and quite good for the street.

Also TKO & TKOII versions of 3550. Ratios are the same, just some improvements & extra power handling 525ft.

That rear end gearing looks a little tall to me, but see how it drives. If you want a cruiser, then it will drive fine. I expect it will still be able to handle slow corners in 2nd gear. If you want it to faster and more tractable off the line etc you will be heading for 3.5 -> 3.9 with 26" diam. rears. As you start moving away from a stock engine and losing your bottom end driveability, you will need lower gearing(3.5+).

The later TKO 500/600 are available with taller 1st gears and more even spread of ratios and lower overdrive ratio.

$2000 for a new 3550 here in Aus sounds like a bargain to me, I would snap it up. T5's used to be cheap, but are getting harder/more expensive to find now.