I am going to pop in some 373 gears in my 94 'stang. It has the automatic with overdrive, and a shift kit. My question is, with the new gears I am thinking my shift points are going to have to be changed. Does the gears shift off the computer, or off a speedo gear? If the gears shift off the computer, does anyone know a good place that will take care of the chipping without taking too long? A place in the Seattle area would be great, but I have no problem sending it somewhere else. Thanks for the help guys!
Brandon, I have 4:10's and was concerned about this also but have come to realize that there is no need to alter the factory shift points. You should though correct the speedometer reading by using a recalibration module or a
21 tooth speedometer gear (driven gear). The shift is computer controlled and appears to be a function of engine rpm and throttle position. For example, under light acceleration the shift occurs at the same engine rpm as before but your mph is lower due to the gear change. Under heavier acceleration to WOT the same principle applies.
You have not hit the rev limiter? Your not driving hard enough or are in need of more power!
The AODE tranny's shifting is controlled by the EEC. The EEC knows how long it takes the transmission to shift. for this example I'll use one second. The EEC also has an acceleration rate programmed into it. Again for example lets say 1000 rpm per second. so in standard form if the tranny should shift at 5000 rpms (under WOT) it would need to send the signal to shift at
4000 rpm so that when it actually shifts the engine is at 5000 rpm. So what happens when you change gears? Yep the acceleration rate goes up. just to keep things simple I'll say it doubles to 2000 rpm per second. (don't we wish!). With no mods to the EEC the tranny is going to send the signal to shift at 4000 rpms expecting it to shift at 5000 rpms. the only problem is in that 1 second that it takes for the tranny to shift your engine will pick up 2000 rpms, or be at 6000 rpms. Your probably asking what's the problem with raising the shift points? The problem is that Ford used cheap POS torque converters that started to balloon over 5500 rpm. Instead of fixing their design so it could run the same 6200 rpm limit as a 5 speed car they just set the rev limiter down to 5250. So now that the shift points have moved up they have actually went passed the rev limiter so when you kick it in the ass and it comes up on that 1-2 shift whamo! the rev limiter kicks in until the tranny shifts and the rpm drops.
If your car original had 3.27 gears and go to 3.73 gears your going to be borderline on this happening with a stock engine. If you car had 2.73s like mine did and/or more power than stock you'll hit it pretty easy.
I know this because I own a 95 GT that had a 342 cid engine and an AODE. Needless to say it wasn't pretty. If anyone is interested I still have the "good" AODE EEC unit and a Level 10 tranny chip for 3.73 gears (will work with 4.10s, but will shift a little higher). I don't need it anymore since swapping to a 5 speed over the winter.
Well, I do drive it hard probably more often than I should. Came with 3:27 gears so the only time I've hit the rev limiter is by locking it in a gear and/or turning off the OD. You are correct about the shift. My 1-2 shift at WOT occurs at about 5200 rpm and the 2-3 at 5000 rpm. As I've installed a High Stall torque converter I would like to find an inexpensive way of over-riding the factory limit of 5250. Will that level 10 tranny chip help me? Let me know.
Richard
'94 GT 'vert Under Drive Pulleys Transgo HD2 Reprogramming Kit High Stall Torque Converter
4:10 Gears Gripp Sub Frame Connectors (welded) Laser Red
Because your car came with 3.27 you would have a little quicker acceleration rate programmed in so that's what keeping you just under the 5250 mark. Since your car is shifting at 5200 on the 1-2 shift your not far from running into trouble. A few more upgrades and you can be hitting a lot more. If you don't plan on any more upgrades than you are probably all right.
As for the chip it changes the acceleration rates as well as shift points. It also raises the shift point to 6500 IIRC. I'm not sure if it does anything with the fuel and timing curves or not. You can check out Level
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