OK, time for some thoughts and ramblings on engine & gearing options.
In current format the car runs and drives great, but in my limited adventures so far (playing in a construction site with some good steep dirt hills) I found myself wanting for a low speed/high torque gear as I was essentially revving up the engine and dumping the clutch to get over some obstacles. In considering my options I compiled the following data from around the web:
basically the 1st and 2nd gear from a b5 1.8T 01a transmission is only very slightly shorter, and 3-5 are identical. When you calculate out the difference it comes out to a delta of 3 MPH at 6,500 rpm which hardly seems worth the effort. Without doing something radical like having custom gears and shafts made for the 01a or trying to adapt a full set of subaru running gear with a real transfer case, I am left looking at other combinations of engine and transmission which would be better suited for the intent of this car.
It just so happens that the day after playing with this car in the dirt, I was out in my V8 swapped CQ playing on the street. Naturally I started thinking about how amazing it would be to have that kind of torque in the lifted car. Then I looked at my spreadsheet with the total cost of that swap and quickly put the idea out of my head. LOL
OK, so if not a V8 then the natural next ideas were (in this order) 5 cylinder 20vt, 2.8 VR6, or 1.8T. AAN/3B is fairly simple but also becoming harder to find and pricy even for a stock motor. 2.8 vr6 is completely do-able but heavy, somewhat more complicated and expensive with adaptation, wiring, engine mounts, etc. That leaves me with thinking about an AEB 1.8T on stock engine management. The AEB is cheap, plentiful, makes great torque (especially with a basic chip tune), and a complete b5 donor car would be very easy to source for ~$500 where I live.
Thinking further outside the box, I think this car is likely one of the rare times when an automatic is actually more fun and a lot more functional than a manual transmission.
An automatic will allow me much better control at low speed and I can tune lockup to the motor by using a higher stall torque converter if needed. This is all pretty important for technical driving in challenging conditions and should help smooth out normal/daily driving with this thing as well. Win-Win.
Wanting to make sure I wasn't going crazy and missing something, I called Scott @ Advanced Automotion for some expert advice. We had a long conversation and he confirmed that had already found the lowest gearing available in compatible audi gearbox. He also posed out the idea of using the a 30v 2.8 V6 from a b5 for powerplant since it makes good torque and is quite reliable, but is about 40-60 lbs heavier than a 1.8T. Scott also gave me some great insight on the 5-speed auto gearboxes from the b5, saying that with just a simple fluid change and new seal kit in the valve body I can expect it to be reliable, robust, and not a complete slush-box. Encouraging.
Ultimately we settled on what seems like it will be the best option: chipped 1.8T, 5 speed tiptronic transmission, and a custom higher stall torque converter from Scott to exploit maximum torque output of the 1.8T at torque converter lockup. As you can see in the table posted above, the gear ratios for the auto box are near-as-makes-no-difference identical to those of the manual trans, and actually even has a slightly taller 5th gear for freeway cruising. I think this is a good plan.
Now to start looking for cheap donor cars without my wife killing me.... I may need to wait a little while and let her forget that she didn't hardly see me for the last 4 months while building this thing to where it is now
