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Old 10-08-2008, 09:28 AM   #1
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Transmission swap

I've been doing a little research and decided that my next FE modification will be a transmission swap. But not to a manual transmission.

I'm going to pull the A44DE Aisin transmission out and put in an A350E Aisin 5-speed automatic. Surprisingly, aside from a tail shaft, it bolts right up! This is also giving me an opportunity to build a custom transmission controller and have a REALLY good FE focused transmission shift scheme. I plan on having two schemes. Normal(FE oriented, WOT only takes you to peak torque) and Power (more like your normal automatic transmission shift patterns except WOT will actually take the engine to 100 or so rpm before fuel cut).

Old Gears
1st - 2.45
2nd - 1.45
3rd - 1.00
4th - 0.73
70mph - 3017rpm
40mph - 1724rpm

New Gears
1st - 2.804
2nd - 1.978
3rd - 1.531
4th - 1.000
5th - 0.705
70mph - 2914rpm
40mph - 1665rpm

I get a wider set of gear ratios. Taller first gear and a better overdrive ratio which only drops my rpms by about 100 on the freeway but the 5 gears gives me more wiggle room. This is getting done before the turbo gets slapped on.

I'd wanted to sell the car but I won't get much of anything for it so I might as well just modify it to hell and back. This is obviously a longer term project. Much like the turbo project. Probably going to get installed after winter when I don't need the car full time anymore.
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Old 10-08-2008, 11:25 AM   #2
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Looks like fun. Being able to modify shift patterns is great for FE.
You're actually getting a shorter first gear with the auto trans. Dropping 100rpm at 70mph isn't a big difference, and the torque converter might consume enough power to offset the benefit of the gear ratios. For comparison, I swapped 5th gear in my trans and the rpms dropped by 600 at 70mph, from 3500 to 2900rpm.
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Old 10-08-2008, 12:08 PM   #3
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I'm thinking about trying a 4.10 rear end in the car with this swap, as opposed to the 4.62 currently in it.

A 4.10 rear end would have me turning 2586 @ 70 (431rpm less) and 1478 @ 40 (246rpm less) with the new transmission and I currently top 1st gear (6500rpm) at 44.93mph and with the new transmission and 4.10s i'd be looking at... wait for it... 44.23. So I'm not losing any low-end gearing whatsoever!

At that low of a highway gear the little 4 banger will definitely want a turbo as it has trouble as it is sometimes turning 3000 at 70. BUT the new transmission with a 4.10 when the car is out of overdrive into 4th is still only 3700 rpm at 70 (instead of the 4200 on the 4.62 rear end). That's actually almost perfect.

If I want to get REALLY advanced on it I can also make the mode selection switch change the way a standalone engine management unit behaves as well. Including turbo boost levels.
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Old 10-08-2008, 01:28 PM   #4
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That's some cool stuff. It's fun when you have control over more parts of the car. A nice thing about an auto trans is that you can run really tall gearing and still get nice power on the freeway because the trans will automatically downshift when you need it. So you can be cruising in top gear, then when it's time to pass or climb a hill you get 4th gear.
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Old 11-06-2008, 09:30 AM   #5
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This is just a note for my own info(thinking out loud). But, I would like to say that I'm happy where the engine lands after a shift more on the 5 speed than i do the 4.

4-speed gear ratios -> Final w/ stock 4.62 -> Top road speed @ 6500 -> RPM after WOT shift
1st - 2.45 -> 11.31 -> 44.9
2nd - 1.45 -> 6.70 -> 75.9 -> 3846
3rd - 1.00 -> 4.62 -> 110.0 -> 4482
4th - 0.73 -> 3.37 -> 150.7 -> 4742

5-speed gear ratios -> Final w/ 4.10 -> Top road speed @ 6500 -> RPM after WOT shift
1st - 2.804 -> 11.48 -> 44.2
2nd - 1.978 -> 8.11 -> 62.4 -> 4581
3rd - 1.531 -> 6.28 -> 81.0 -> 5006
4th - 1.000 -> 4.10 -> 124.0 -> 4245
5th - 0.705 -> 2.89 -> 175.9 -> 4581

Lowest possible TC lock speeds by gear(MPH@1500rpm*) <- Actual programmed lockup logic per gear.
1st - 10.2 <- set 'tccl' = "0"
2nd - 14.5 <- if 'vss' gte "14.5" and 'tps' gte "50" and 'sss' gte "1" set 'tccl' = "1" else set 'tccl' = "0"
3rd - 18.7 <- if 'vss' gte "18.7" and 'tps' gte "50" and 'sss' gte "1" set 'tccl' = "1" else set 'tccl' = "0"
4th - 28.6 <- if 'vss' gte "28.6" and 'sss' gte "2" set 'tccl' = "1" else set 'tccl' = "0"
5th - 40.6 <- if 'vss' gte "40.6" and 'tps' neq "0" and 'ssl' gte "2" set 'tccl' = "1" else set 'tccl' = "0"
(*Lower locked TC rpm results in shuddering under load)
VSS - Vehicle Speed Sensor
TPS - absolute Throttle Position Status
SSS - Seconds Since last Shift
SSL - Seconds Since last Lockup

Most driving will not see TC lockup until 40.6 mph unless held out of overdrive in which case 28.6 is the lowest. WOT minimum lock speed is 45MPH and each gear will lock as they are shifted into(lockup waits 1-2 seconds after gear is entered before activating unless in overdrive, then there is a 2 second delay after last lockup).

Overdrive will unlock TC at idle to allow longer coasting and TC will lock under heavy load in all gears except 1st to increase power transfer and lengthen the amount of time spent in a lower gear. 2nd and 3rd must be under heavy load to lock to keep unpredictability of torque transfer during TC lockup from causing winter drivability issues.
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Old 11-11-2008, 02:04 PM   #6
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I gotta admit, I'm not liking the in-town overdrive lockup speed. Most roads around here are 35 and 40.

I think I'd prefer the 5 speed in front of the stock 4.62 rear. Won't give me much of a freeway rpm drop(100rpm) but that'll allow me to lockup overdrive as low as 36mph as opposed to 41. hmm

Locking 4th on the 5 speed with a road speed of 36 gives me 1887rpm or I stay in overdrive with an unlocked converter. boo.
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