I was driving my truck the other day and threw it in neutral going down a big hill and noticed that it doesnt rev the motor to match your speed like it used to, any ideas why it doesnt anymore?
LB7: neutral rpm matching
- Thread starter MuscleTruck03
- Start date
This thread is confusing. Last I knew when or if you pop it into neutral the Tach should drop off to idle RPM? Now I don't drive my truck very often but last I recall ,me confused?
So it's not suppose to do,what?
So it's not suppose to do,what?
When i throw my truck in nuetral going down a big hill the rpms will rise the faster i go, not the same as if it were in gear but defiantly above a sitting idle
Likewise, mine does the same. However, mine seems to match the rpm as if i were in gear. When i slip it backminto gear there is no change in rpm.
its called "neutral tracking."
When you put it in neutral, depending on what gear/speed you're at, the TCM will continue to keep the engine at the proper rpm for smooth re-engagement into drive.
Its basically like rev-matching a manual transmission. If you were at 60mph and put the trans into neutral, and the engine went down to idle, and then you shifted back into drive still at 60mph, there would be a huge clunk/shudder/stress on the trans as the engine was suddenly brought back up to proper RPM.
Neutral tracking prevents this...holds the engine at the desired RPM for smooth shifting back into a range from neutral.
If you were not in lockup at the time (below 50mph), neutral tracking isnt as obvious. Becuase when the trans isnt in lockup and you let off the gas pedal, engine rpm drops down to idle...because thats what a torque converter equipped automatic trans does. So if you are below ~50mph in non-tow/haul mode, and you let off and the engine drops down to idle speed, and you shift into neutral, theres no reason for the TCM to use the neutral tracking feature aggressively because when you shift back into drive (non-lockup), the engine rpm is going to be close to idle anyways.
If that makes sense.
When you put it in neutral, depending on what gear/speed you're at, the TCM will continue to keep the engine at the proper rpm for smooth re-engagement into drive.
Its basically like rev-matching a manual transmission. If you were at 60mph and put the trans into neutral, and the engine went down to idle, and then you shifted back into drive still at 60mph, there would be a huge clunk/shudder/stress on the trans as the engine was suddenly brought back up to proper RPM.
Neutral tracking prevents this...holds the engine at the desired RPM for smooth shifting back into a range from neutral.
If you were not in lockup at the time (below 50mph), neutral tracking isnt as obvious. Becuase when the trans isnt in lockup and you let off the gas pedal, engine rpm drops down to idle...because thats what a torque converter equipped automatic trans does. So if you are below ~50mph in non-tow/haul mode, and you let off and the engine drops down to idle speed, and you shift into neutral, theres no reason for the TCM to use the neutral tracking feature aggressively because when you shift back into drive (non-lockup), the engine rpm is going to be close to idle anyways.
If that makes sense.
Interesting although i don't recall popping it in to neutral and coasting, I'd assume the tach would drop to near idle.
Guess next time I drive my truck ,who knows when or if I remember this,I'll try it.
Guess next time I drive my truck ,who knows when or if I remember this,I'll try it.
That's what I thought. If the TC unlocks RPM drops. Therefore I assumed ,their I said it,when neutral is selected the TC unlocks. No? Thats why it makes no sense to me
But there again what do I know
Only did it just recently and was going about 70mph if that helps, ya mine always matched so when I'd throw it back in gear it was fine, this time with no rev matching it was a little harsh going back into gear Would it have something to do with the trans tune?
Would it have something to do with the trans tune?
haha after it smacked into I gear I havent done it since and I did it in hopes to save a tiny bit of fuel, I have to go up and then down a looonnngg canyon and at 70 my tc is locked, so I have to stay on the throttle decent just to go down hill
and I did it in hopes to save a tiny bit of fuel, I have to go up and then down a looonnngg canyon and at 70 my tc is locked, so I have to stay on the throttle decent just to go down hill
My tranny would "neutral track" before I had it built, now it will clunk real bad, no matter what tune I have on the tcm.
Edit: doesn't bother me I just happened to notice it one day.
Edit: doesn't bother me I just happened to notice it one day.
you arent going to save any fuel. Actually you're going to burn MORE fuel. Because when you let off the throttle and are coasting with the engine at higher rpm's, the engine goes into DFCO mode and totally shuts off the injectors (log it), thus using ZERO fuel.
When you shift into neutral, "neutral tracking" becames active, and the engine uses fuel to keep the rpm's "sync'd" with the trans turbine speed.
So the whole "shift to neutral to save fuel" is totally false.
ben
When you shift into neutral, "neutral tracking" becames active, and the engine uses fuel to keep the rpm's "sync'd" with the trans turbine speed.
So the whole "shift to neutral to save fuel" is totally false.
ben