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47re Overdrive discussion


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2001 24v auto 47re

truck seems to not want to shift into overdrive untill 55+ mph at light throttle. Wondering what other people experience with their trucks. I have 36" tires and 3.55 gears but my speedo is only 2mph fast verified with gps. It will shift most times at 57mph on the speedo and 55mph shown on my scanner reading the VSS.  

From what I've researched overdrive is controlled by PCM once the apps, trans temp, output speed sensor parameters have been verified and not by the adjustment of the tv cable or fluid pressure. (Could be wrong). I drove with the scanner hooked up and verified the overdrive shift happens when voltage drops to the 3-4 shift solenoid at 55mph so it's working as designed. Is there a way to lower the overdrive shift speed? Even with the tall tires and tall gears it seems I'm always driving around town in 3rd gear locked around 2k rpm. I can get it to shift into 4th by letting off the throttle quickly above 40 mph but that gets annoying. I've searched and searched for days but didn't really come up with a solution.

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I had the speedo calibrated perfectly when I had the smarty tuner but recently sold it and bought a quad adrenaline. It seemed to shift around 50mph when I had the speedo perfect. I'm not sure if it had been calibrated before I got the truck and is 3mph off or what. I'm trying to figure out a way to fix the speedo calibration without having to go to the dealer but not coming up with much luck. Is the only way to reflash the abs for speed correction with a dealer DRB3 is another question I guess.

Trying to get an idea where other peoples 4th gear shift is. Driving it with the 4th shift @ 55mph doesn't feel normal. It's @ 2k rpm and just feels like I'm waiting for it to shift the whole time I'm driving. Most of my driving is 45-50mph so it's in the top of 3rd gear all the time. I can get it to shift if I let off the throttle for a second over 40mph but that gets annoying. 

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I believe that TOS speed vs throttle is what's used to determine when the trans will shift in OD, which means speedo calibration doesn't have much to do with it. The higher the throttle the higher TOS is needed to shift, which is why it will shift if you release the throttle. 

 

 

 

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29 minutes ago, AH64ID said:

I believe that TOS speed vs throttle is what's used to determine when the trans will shift in OD, which means speedo calibration doesn't have much to do with it. The higher the throttle the higher TOS is needed to shift, which is why it will shift if you release the throttle. 

 

 

 

In my 3rd scanner screen shot the output shaft speed (1960 rpm) is very close to engine rpm (1952) in 3rd gear which makes sense because 3rd is 1-1. In the 4th screen shot you can see the shift happened because output shaft speed went to 1980 rpm but now engine rpm is 1344. I took pics at both those moments because the shift happened @ exactly 55mph. I'm not sure what the throttle position sensor voltage does in relation to what's going on with output shaft rpm, engine rpm and vehicle speed. I guess I've got the information in front of me but am just guessing at what is really going on to make it decide to shift. 

Another thing I read and I think this screen shot shows is the governor pressure seems to be messed up. The desired pressure column compared to the actual is way wrong. This is a screenshot of a video I took and in the video the actual governor pressure makes wild erratic swings. 3 to 14 to 34 to 8 to 2 to 12... ect ect while the desired pressure stays constant and smooth. This makes me believe I need to replace the governor solenoid but with 4th gear shift being electric and controlled by the pcm does this really matter. The scanner stops recording desired pressure after 40mph and it stays at 127 while the actual pressure stays 60-70 plus during the 3-4 gear change. I'm not sure if I should throw a governor solenoid at it and see? I just hate throwing parts without learning exactly what's going on. 

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Gov pressure increases as TOS speed increases and it is what determines the 1-2 and 2-3 shifts. Are those happening correctly?

 

On 3rd gen 48RE's the Gov pressure is set to go to 127 at 1800 rpms for the TOS and then stays there, which is why it stays in 3rd gear. The WOT shift pattern waits to go to 127 until 1920 TOS rpms. 

Your desired pressures seem to match 3rd gen pressures, but as you noted the actual pressures are quite a bit off. 

 

For reference this is a 48RE from 2004.5. It's reference only, but from the looks of your screen shots it's pretty close if not the same. 

 

 

Gov PSI.JPG

 

Here is the relationship of throttle to the 3-4 shift on a 48RE. Based on the gov psi similarities I'd guess this is pretty similar too. 

 

 

throttle.JPG

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2 minutes ago, Kodiak24V said:

The 1-2 shift cold first thing in the morning sucks. It has trouble and kind of surges. 1/2 mile out of my neighborhood it cleans up and shifts great. 

 

That could be a gov solenoid, but I agree that throwing parts at something sucks. 

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The last screen shot is the 2nd gear shift where the target pressure is 10 and actual is 28 but really is jumpy and all over the place. But does the gov pressure have anything to do with 3-4 shift? I'm not sure? The actual pressure stays at 69-70 at part throttle 1900 plus rpm when it finally completes 3-4 shift. Is 69 actual pressure to low to make the shift? Once the pcm drops the voltage to the overdrive solenoid it shifts 3-4 instantly. Just don't know what the pcm needs to see to make that happen.

This is a screen shot of the moment target gov pressure hits 127. Not sure what to make of it

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I'm not sure the gov pressure has anything to do with 3-4 shift. The scanner shows the duty cycle of the gov press sol at 0 once it shows 127. And I didn't see any pressure change when the shift happens. I could be wrong, I'm just guessing.

37 minutes ago, AH64ID said:

Gov pressure increases as TOS speed increases and it is what determines the 1-2 and 2-3 shifts. Are those happening correctly?

 

On 3rd gen 48RE's the Gov pressure is set to go to 127 at 1800 rpms for the TOS and then stays there, which is why it stays in 3rd gear. The WOT shift pattern waits to go to 127 until 1920 TOS rpms. 

Your desired pressures seem to match 3rd gen pressures, but as you noted the actual pressures are quite a bit off. 

 

For reference this is a 48RE from 2004.5. It's reference only, but from the looks of your screen shots it's pretty close if not the same. 

 

 

Gov PSI.JPG

 

Here is the relationship of throttle to the 3-4 shift on a 48RE. Based on the gov psi similarities I'd guess this is pretty similar too. 

 

 

throttle.JPG

 

37 minutes ago, AH64ID said:

Gov pressure increases as TOS speed increases and it is what determines the 1-2 and 2-3 shifts. Are those happening correctly?

 

On 3rd gen 48RE's the Gov pressure is set to go to 127 at 1800 rpms for the TOS and then stays there, which is why it stays in 3rd gear. The WOT shift pattern waits to go to 127 until 1920 TOS rpms. 

Your desired pressures seem to match 3rd gen pressures, but as you noted the actual pressures are quite a bit off. 

 

For reference this is a 48RE from 2004.5. It's reference only, but from the looks of your screen shots it's pretty close if not the same. 

 

 

Gov PSI.JPG

 

Here is the relationship of throttle to the 3-4 shift on a 48RE. Based on the gov psi similarities I'd guess this is pretty similar too. 

 

 

throttle.JPG

In this graph it shows tps @ 16% the shift should happen 1640 TOS rpm. I'm guessing but my part throttle cruise should be somewhere around 16-20% and @ 1960 TOS rpm is when it finally shifted. On that graph 1960rpm is around 52% tps. I'm barely touching the throttle is the strange part. It should be shifting way sooner. 

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Gov pressure shouldn't have any impact on the 3-4 shift. The 3-4 shift is all electronically controlled and the trans stays in 3rd gear but the OD module is activated. 

 

Do you have any tuning that impacts throttle sensitivity? This can effect shifts from what I recall. 

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1 minute ago, AH64ID said:

 

As far as I can tell yes. If there is anything else it's minor. 

Do you think it's possible to change the 3-4 shift  by playing with the tps? It's just weird that it shifted like clockwork @ 50mph with the smarty tuner and the tire size/speedo calibration dialed in. Then once I removed it and put on the quadzilla it's now way later @ 57mph. If I look at the scanner 50mph is right around 1750 TOS rpm just like the 2nd graph you posted for 20ish tps %. I'm not sure why the change happened that it now shifts @ 1960 TOS rpm?

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It has to be something with the TPS signal. Likely the smarty commanded more fuel from less throttle, which means the OD shift would happen sooner for the same acceleration rate. 

 

I’m tuning an 06 now that is going thru the same thing. We switched from a S-JR UDC tune to a UDC Pro tune and it shifts into OD later. I’m working a retune for his 3-4 shift this weekend.

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Makes me wonder what the actual tps voltage needs to be to engage the shift. It's 1.23v on tps  and 1960 TOS rpm for mine to shift now according to the scanner. Bummer it only gives tps as a voltage and not a percentage. I did do a tps reset to make sure. And I have played with the tps/apps throttle stop to get it closer to the value on the sensor.  I can change canbus fueling with the quadzilla wherever I want. I can max out canbus fueling at 0 psi boost pressure but I'm not sure I see how that will change tps voltage the pcm sees. The throttle position voltage should be the same no matter how much fuel is being requested.

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Not sure I understand why letting off the throttle will get it to shift 3-4 either. It happens every time instantly. When I watch the signal from the pcm to the od solenoid it commands the shift instantly as soon as I let up. Every time over 40 mph. 

1 minute ago, AH64ID said:

The TPS signal won’t change, what I’m fairly certain the Smarty does is command more fuel at lower TPS values so with the Smarty you’re getting 50% fuel at 30% throttle... just arbitrary numbers to make a point. 

I understand what your saying but if the pcm looks at TPS voltage and TOS rpm to command the shift adding more fuel at a certain tps range won't do anything but change the load on the engine right? It won't change the tps voltage the pcm sees and I don't think the trans monitors engine load. (Could be wrong). Something happened when I changed to tire size and got the speedo right with the smarty. I had this problem when I 1st got the truck, it drove me nuts, I got the smarty and I could 100% guarantee every time the 3-4 shift would happen @ 50mph on the speedo. Then I removed it and now it shifts at 57mph, some times @ 48mph, some times 54mph. It's really baffling and I'm the type of person who has to understand how something works and the reason things do what they do, and it's driving me insane...lol I just can't find any information anywhere to tell me exactly what the pcm looks at to engage the shift. I know it's shifting exactly when the pcm says I just can't find the exact parameters it uses to determine when. 

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