I'm having new gears installed because they are going out and want to put 4.10's on my 99gt auto but don't have the money to get a programmer at the same time.. besides the speedo not being accurate, will this cause any problems? would I be able to drive or would the shift points be all screwed up? if so, is there an easier way to get around it instead of a 400$ programmer? Thanks
gears on automatic with no programmer?
- Thread starter fswd
- Start date
I'm not too sure about the shift points myself, but I know your odometer will be rolling over more miles than you are actually putting on the car. You can get a Dallas Mustang Speedcal
for pretty cheap there, or if you haven't gotten your gears yet, get this kit.
Let us know what the difference in cruising RPMs are for you between the gears. Good luck, and 'grats on the gears!
for pretty cheap there, or if you haven't gotten your gears yet, get this kit.
Let us know what the difference in cruising RPMs are for you between the gears. Good luck, and 'grats on the gears!
speed545
Member
I ve always run the car with the tune in it except for a few times. I didnt notice any majors changes in the shift point set up. I will not say it doesnt make a diff but for the few meters i did with the car, i did not remark anything.
speed545
Member
Don 95Vert
Founding Member
Shift points and converter lockup WILL be way off. This is because the shifting and converter lockup are MPH based and if the MPH is off, the shift points are off. WOT shifting does have RPM trigger points, but if the MPH shift point is reached first at high TP, then the transmission shifts at whichever it hits first - and with gears, that'll be the high TP/High MPH points at WOT.
Don 95Vert said:
I agree, with a stick you can get away with out calibrating the spedo but not in a auto.
propellerhead
New Member
I wouldn't say WAY off. I have 4.10s on a 4r70w and I ran an entire week with my stock tune. The speedometer is off, but shifting is quite normal. I don't think it really calculates it on the MPH as seen by the speedometer. I believe it calculates it via the driveshaft rotation speed or something that isn't affected much by the final drive ratio.Don 95Vert said:
I have 3.73 and an auto and NO tune or speedcal. You can get away with it for a short time being that i've driven mine like that for 5 years. My speedo is only off alittle. I did just order a speedcal.
The shift points are calulated based on VSS inputs and rpm inputs. they don;t change a lot untuned but they will change. he amount o the change depends on how steep the gears are
you can drive around with 4.10's without problems for the most part. but i wouldn't advise it.
the car will drive fine because the shift points and torque convertor functions are programmed by MPH and throttle position for normal driving. so if the car normally shifts from 1st to 2nd at 20mph with 3.27's, it will shift at what it thinks is 20mph (actually 16mph) with the 4.10's. WOT shifts are programmed by RPM. this is a little more of a concern than normal driving shifts. with the 4R70W, there are Commanded shifts and Actual shifts. what that means is that the computer "commands" the shift at say 5000rpm but it takes the transmission about 1.5 seconds to fill up the clutches needed to make the shift. in that 1.5 seconds of time, the RPM rise another 1000rpm to 6000rpm. so even tho it's commanded at 5000rpm, the actual shift is at 6000rpm. now when you add alot of power OR change the gears, it increases how fast the RPM climb. just for reference, let's say that instead of climbing 1000RPM in that 1.5 seconds it takes to fill the clutches, it now climbs 1500rpm. your new actual shift point will be 6500rpm. you'll start banging against the rev-limiter. a new tune can lower your commanded shift from 5000rpm to 4500rpm to compensate for this. so between that and the 20% or so extra odometer mileage you'd be putting on the car, i highly recommend you get it tuned. and don't forget a tranny cooler.
the car will drive fine because the shift points and torque convertor functions are programmed by MPH and throttle position for normal driving. so if the car normally shifts from 1st to 2nd at 20mph with 3.27's, it will shift at what it thinks is 20mph (actually 16mph) with the 4.10's. WOT shifts are programmed by RPM. this is a little more of a concern than normal driving shifts. with the 4R70W, there are Commanded shifts and Actual shifts. what that means is that the computer "commands" the shift at say 5000rpm but it takes the transmission about 1.5 seconds to fill up the clutches needed to make the shift. in that 1.5 seconds of time, the RPM rise another 1000rpm to 6000rpm. so even tho it's commanded at 5000rpm, the actual shift is at 6000rpm. now when you add alot of power OR change the gears, it increases how fast the RPM climb. just for reference, let's say that instead of climbing 1000RPM in that 1.5 seconds it takes to fill the clutches, it now climbs 1500rpm. your new actual shift point will be 6500rpm. you'll start banging against the rev-limiter. a new tune can lower your commanded shift from 5000rpm to 4500rpm to compensate for this. so between that and the 20% or so extra odometer mileage you'd be putting on the car, i highly recommend you get it tuned. and don't forget a tranny cooler.
speed545
Member
DBMSTNG said:
+1
This is why i lowered my 1-2 and 2-3 shift by 500RPMs. I was hitting rev limiter each time i floored it from 1st.
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