Can i drive my auto after having gears installed but not having the ECU reflashed?

aj1025

New Member
Jul 4, 2003
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Tyler Texas
I 'm going to order some 4.10 gears tommorow and found a place to install them for $200.00, i'm just wondering can i drive my automatic gt around with just the gear change until i can have the ecu reflashed, or will the car not shift right? I know the speedo will be affected until the relash, but what about the shifting of the tranny, will the 4.10 gears mess up my tranny without having the reflash done to adjust for new shift points. I just don't want to mess up my tranny, i know i should have all this done at once but i can probaly come out in the long run having the install and reflash done seperately. How much is the average reflash for having gear change, just curious? Thanks for any info.
 
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Hey I'm planning on getting my 4.10 install next week also.. I've also found a shop that will install them for $200.. are you talking about The Mustang Shop in Dallas? Because that's where I'm going..

As for the ECU reflash.. I'm going to send it to T&J Performance in Georgia and have them do it for $300.. :nice:
 
aj1025 said:
As far as having the shift points changed could i just use a HYPERTECH to change my shift points after having the gears installed? Hey thanks for all the info everyone.


Yeah you can change your shift points and correct speedo with a programmer.You're looking at 300+ dollars any route you go.
 
GTvert01 said:
I wouldn't think it would affect your tach, but your mileage odometer will be off.

That's what I thought. It brings another question though, doesn't the ECU rely on the RPM and not the speed to decide when to shift ? :shrug: If so, why would a different gear mess with the shift points.

BTW, I know the shifting decision takes throttle postion and load into account.
 
Avenger said:
That's what I thought. It brings another question though, doesn't the ECU rely on the RPM and not the speed to decide when to shift ? :shrug: If so, why would a different gear mess with the shift points.

BTW, I know the shifting decision takes throttle postion and load into account.

I would say both and probably more input are needed to advise the tranny to shift. Your auto tranny never shift at the same RPM depending on how hard you get on the gas pedal. :)
 
auto trans has a vehicle speed sensor that the ecu uses for shift point as well as rpm so your trans will shift at the same point as stock but in reality your ecm will think the car is going faster than what it actually is until you get the recal
 
Avenger:

The '98 uses a vehicle speed sensor (VSS) and an output shaft sensor (OSS). My understanding is the VSS is for the speedo/odo and the OSS is for the shift points. The OSS 'table' will not be correct for the engine speed vs. OS speed with the new gears.
 
aj1025 said:
As far as having the shift points changed could i just use a HYPERTECH to change my shift points after having the gears installed? Hey thanks for all the info everyone.


i believe you can....i used my superchips to reprogram mine after i had the 4.10's installed...but if you don't do it and wait, your car will be shifting funny...
 
If I remember right it will effect your top speed too. I remember someone posting a dyno run that wouldn't go over 73 or something like that and it was due to his lack of speed cal after changing gears...
 
Drive as little as possible before you get a ECU reflash for shift points and speedo. It will really mess up your transmission... I found this out the hard way after only driving about 1,000 miles I had to have my transmission rebuilt (had 80,000 and it was an auto).

Go ahead and do it right- send you computer to T&J for a reflash.
 
Looks like i want be getting a gear change as soon as i thoought i would, since i know i can't drive the car with just a gear change and not having the reflash. Autos suck on the gear change because it cost so much more than the 5 speed gear change, i can't come up with $600.00 for a gear change plus reflash all at once. I'm glad i didn't order my gears yet because they would be collecting dust in the closet because of how much the total install will cost all at once.