ap2 5th and 6th gear in ap1 tranny
 

Im not sure if this is the right place to post this but i was wondering if the gears are interchangeable between the ap1 and ap2 gearboxes. I want to put the ap2 5th and 6th for their lower ratio into the ap1 gearbox and possibly run a 4.4 rear end. this is of course in effort not to wind my motor to the moon on highway drives. it is from my understanding that the ap2 tranny while 5th and 6th are lower, the highr ratio reduction gear puts the rpms at about the same. hence why id like to swap them to the ap1 tranny.

You might consider a second option and just swap the ap2 trans in all together. The primary gear reduction of the ap2 trans will give you some gear multiplication (not as much as a 4.44) But works out to a 4.22 equivalent over the stock 4.10. Then you still get the better 5/6 overdrive gears. Its actually a nice factory improvement for the F20 if the factory did it in hindsight.

Hardly seems worth the effort, IIRC the AP2 6th is only ~4% taller than AP1. AP1 has closer ratios throughout, which IMO is better, but it's not a huge difference and again hardly worth the $$$/effort if you ask me...

Save your time and money, you'll only be going from 4000rpm to 4300rpm at 75 on the highway.

Why do you want a 4.44 diff anyway? If it's for any reason other than specifically improving 0-40 acceleration, maybe you shouldn't... Power/weight doesn't change, overall performance doesn't either. 0-40 will improve, but 0-43 will be slower due to having to upshift. Same thing through the gears. Changing diff gearing is IMO one of the most overrated mods.

The F20 is a pretty low trq motor, so I get the desire to snap it up a bit with a lower ratio to a degree. 4.44 is a good option because it will still get you to 60mph in one shift, improving your 0-60 acceleration and still maintaining a decent mph spread between gears. With the added trq of an F22 (especially a lowered vtec/tuned one such as myself) I would not touch the gears, especially when considering the lower rpm/mph. In fact with the 315 rear I'm on it effectively dropped my final drive to a 3.97 and I actually like it quite a bit. If I had a stock f20 under the hood I likely wouldn't, so there is some room to play around in there. These mods all cost something though, so should weigh everything out to see if its really worth it. Ive had my car so long, I just wait till something blows and make the change then. No sense in modding/replacing good working parts prior to that is my feeling.

I currently have an ap2 tranny in the car. My ap1 tranny is sitting in my garage in good shape. It was just an idea. Im pretty mechanically inclined as ive rebuilt motors, but ive never taken a tranny apart before. Im just looking for a little more punch from a 4.44 but dont want to raise my cruising rpm too high.

So you would be basically running a 4.56 rear end then with that combo for the first 4 gears. Not sure id care for that myself, but some like the way it feels. 0-60 will suffer because you will no longer make it to 60mph in 2nd gear.

If you want lower (numerically higher) 1-4 gears and longer 5-6 gearing, you've already got that with the AP2 gearbox. Putting AP2 5th and 6th into the AP1 gearbox and running that with 4.44 diff gearing isn't going to be terribly different overall from AP2 trans with 4.44 gears. The taller transmission gearing partially negates the change from 4.1 to 4.44. I get this for speeds in gears:

AP2 trans with 4.10 diff = 42/65/90/114/141/174, 75mph cruise at 3841rpm
AP1 trans with AP2 5 and 6, with 4.44 diff = 41/62/86/110/135/167, 75mph cruise at 3995rpm

It's essentially the same thing as if you just kept the AP2 trans and went with 4.26 diff gearing.

You're making two changes, one of which is canceling more than half the effect of the other! Seems a lot of effort to not change things much...

So between ZDan and I you should be armed with enough info to decide if its worth the cost and trouble to you. I think you know what our opinion is on the matter - and yet, we still managed to dodge your original question. Your welcome :p

We've been doing AP1 tranny with AP2 secondary gear to get the shorter gearing of the AP2 gears...but, you can also do the reverse.

AP2 tranny with AP1 secondary gear will give you 1st-4th like an AP1 (good if you have a high hp motor, or for most tracks in CA), yet gives you the longest 5th and 6th possible for highway cruising.