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Question regarding about on AT


GkLapp
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Hello, Is it normal for the vehicle when the selector lever on drive would not hold engine rpm?

 

I run 40kmh at 2500 rpm at drive while my foot is on the gas, then as soon as I let off the gas pedal, the engine rpm would then drop to somewhere around 900-1000 rpm however there seems to be no engine braking in this period although the vehicle would slow down. Although the engine rpm would run again at 2500 rpm if the vehicle's speed is close/near to 40kmh or if the vehicle's speed is at 30 kmh with the engine rpm is somewhere around 2000 rpm if I would step on the gas pedal again, stepping it lower and lower until I can feel the vehicle is slightly accelerating.

 

The 1,2 and R position holds engine rpm and I can feel the engine braking.

 

Would be greatly appreciated to anyone who can answer. It's been hovering on my mind ever since I drove the vehicle.

 

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That does seem normal to me. In reverse, 1st and 2nd the transmission is 'locked' in that gear choice. In drive there are at least two other gear options for the transmission control unit to choose from, which it will do according to its programming, in concert with the overriding control of engine operations from the engine control computer (tuned for regular street driving and fuel efficiency). That being said for a V6 from the 1990's it's not really that efficient compared to anything current.

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Engine RPM will change with load as the transmission shifts up and down and the torque converter locks and unlocks. When you want more engine braking, turn off overdrive (button on the shifter). This locks out fourth gear. I think it alters the converter lockup behavior as well, but I'd have to look that up again to be sure.

 

I turn off the overdrive when I'm climbing or descending mountain passes. This gives me better engine braking and stops the trans from going for overdrive at stupid times on the way up.

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  • 5 months later...

Thanks, I thought it seemed not normal to me as other newer automatic vehicle I observed holds their engine rpm as soon as the gas pedal is lifted. Mine is a diesel version, td27 turbo specifically. 

 

I tried also doing turning off the overdrive, but it seems it does not have any noticeable engine braking. Though it's certainly stupid for the tranny to go overdrive on uphill.

Instead, when the OD is off, I feel the engine rpm kind of neutral? Pressing the gas, rpms rises up but the vehicle is not going faster. So when the OD is on again, instead of that neutral feeling, it just slips,  and very sluggish acceleration. It occurs at 1-2 upshift

 

This tranny seems to hold problems, like having no 2-3 upshift or 2-4 upshift as if this tranny has no 3rd gear or 4th gear, forget 3-4 upshift, all happening on D gear selector and also there's the 1-2 upshift neutral. In fact I select 2 on the gear selector as my normal driving mode as 1-2 upshift is fine, though it does makes me run at lower speeds. It also likes to leak atf at the bellhousing, near the starter motor. It certainly makes me hate to work underneath as everywhere I touch, I would have that dirty sludge.

 

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Yeah, that doesn't sound healthy. First thing I'd check is the fluid level, it might just be having issues because it's low (due to the leak at the bellhousing). Check it running, warm, after going through each gear. Seems like low fluid would cause issues in all gears, though. Not going into third or fourth makes me suspect it may have a solenoid issue, but I haven't dealt with that on mine and don't know the trans well enough to say. When you turn the key on, does the POWER light on the dash (or the light in the E-AT switch, depending on which dash style you have) flicker? If it does, the trans computer thinks something is wrong, and there's a procedure to figure out what it's upset about in the service manual. Even if it's not flickering, I would have a look through the AT section of the manual anyway--you may find your symptoms listed in the troubleshooting section.

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