What could make my tranny shift late?
07-07-2005, 03:20 PM
#1
What could make my tranny shift late? I just got a new FLP tranny in my car with a new TCI 3800 stall converter. But it shifts WAY past where I want it to and I don't know why. It's not slipping between gears, and shifts firm when it does. But, for example, my setpoints are 1->2 shift at 37mph & 6000 rpms. But it shifts at 42mph & 6700rpms. 2->3 shift is set at 73mph & 6000 rpms, but shifts at 78mph & 6800rpms. BIG DIFFERENCE. Why? The new tranny is vacuum modulated, but shift points are still controlled thru the ECM, right. What else could effect when the tranny decides to shift. I've modified the normal shift mph, WOT shift mph, and WOT shift rpm setpoints, but it's still overshooting by a lot.
Any ideas?
Any ideas?
07-08-2005, 12:30 PM
#3
I'm using 3.73 gears now. I divided the tire diameter by the rear end ratio (per manufacturer) and let HP Tuners auto scale all the shift tables. As far as comparing them to the actual shift speeds, they seem right. But I noticed that when I'm driving 55mph, HP Tuners says I'm driving like 52. So either the needle on the speedo is off or maybe I'm off a on that ratio a little. But The numbers above were all from HP Tuners logs so that's what the ECU is seeing.
07-08-2005, 01:45 PM
#4
What year is your car?
I'm not sure about 99+ but 98's with a stall require a huge correction factor.
My 1-2 shift point is set at 5575, however the actual shift occours just after 6000rpm.
My understanding is shifts occour off of the input shaft rpm, not the motors, with the addition of a stall there is a bigger difference in rpm between the motor/input shaft thus a larger correction in the shift tables. Hope this helps.
I'm not sure about 99+ but 98's with a stall require a huge correction factor.
My 1-2 shift point is set at 5575, however the actual shift occours just after 6000rpm.
My understanding is shifts occour off of the input shaft rpm, not the motors, with the addition of a stall there is a bigger difference in rpm between the motor/input shaft thus a larger correction in the shift tables. Hope this helps.
07-08-2005, 01:53 PM
#6
LOL that gets me to thinking though. I bet that's the reason my stock tranny was slamming the rev limiter earlier this year. With the newfound 70 additional horsepower, I bet I was just blowing thru the converter... Oh well, I needed this tranny eventually anyway.
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07-08-2005, 03:26 PM
#8
you can start making sure you got everything calibrated proper (EFFECTIVE tire size especially, gearing, making sure tacho reads right).
you can make sure the hardware is right, my trans wouldn't want to do 2-3 WOT, turned out wanted a bit more trans fluid, as under full acceleration the fluid was on the other side of the trans :/
or you can just be a pragmatic bastard and keep lowering the shiftpoints till it shifts where you want it to. not recommended, but it is by far the quickest of methods.
you can make sure the hardware is right, my trans wouldn't want to do 2-3 WOT, turned out wanted a bit more trans fluid, as under full acceleration the fluid was on the other side of the trans :/
or you can just be a pragmatic bastard and keep lowering the shiftpoints till it shifts where you want it to. not recommended, but it is by far the quickest of methods.
07-08-2005, 04:27 PM
#9
Originally Posted by SmokingWS6
My understanding is shifts occour off of the input shaft rpm, not the motors, with the addition of a stall there is a bigger difference in rpm between the motor/input shaft thus a larger correction in the shift tables. Hope this helps.
The Engine RPM is right under 6200 rpms at the 1st -> 2nd gear shift. The Input Shaft RPM is at 5980.5 (97% efficient). By looking at the log, I can up my MPH WOT shift point to 46 and both the RPM and MPH WOT points will corrolate.
Last edited by Flame Throwing SS; 07-08-2005 at 04:33 PM.
07-09-2005, 05:19 PM
#10
Originally Posted by Flame Throwing SS
That is not true, at least on 2001 F-bodies. Below is a screen shot of my log from the track. I am using a B&M 3200 converter, shift points are as follows: 6200 rpms, 40 MPH
The Engine RPM is right under 6200 rpms at the 1st -> 2nd gear shift. The Input Shaft RPM is at 5980.5 (97% efficient). By looking at the log, I can up my MPH WOT shift point to 46 and both the RPM and MPH WOT points will corrolate.
The Engine RPM is right under 6200 rpms at the 1st -> 2nd gear shift. The Input Shaft RPM is at 5980.5 (97% efficient). By looking at the log, I can up my MPH WOT shift point to 46 and both the RPM and MPH WOT points will corrolate.
I think its only a 98 issue. As redhardsupra said it might be the bastard way to set shifts but so far its worked great for me and other 98 with aftermarket convertes, no trans problems at all. Mentally having to type in 5600rpm sounds messed up but i get consistant 6050rpm shifts out of first.
Another thing is I have to overcorrect, i've conversed with many 98 owners about this issue. I can flash in a 5900 rpm shift and have it occour at 6000rpm, but as weeks go by the shift pt will occour higher and higher untill I hit the limiter. If I over compensate as the weeks go by it'll stop raising its self at 6000rpm or so. Good old bastard child 98's
