LX Power drop between gear changes is this normal?

[xlr8it]

Hi All,

I have had my 99 LX470 for six months and I am not sure if this is normal.

It tends to drop a little bit of power between gear changes almost like a flat spot , but it only does it when it is pushed hard (say over 3500 rpm) ,as if to make the gear changes smoother.

Is this normal or do I have a problem?

Thanks
Leon.

 

[spressomon]

Hi All,

I have had my 99 LX470 for six months and I am not sure if this is normal.

It tends to drop a little bit of power between gear changes almost like a flat spot , but it only does it when it is pushed hard (say over 3500 rpm) ,as if to make the gear changes smoother.

Is this normal or do I have a problem?

Thanks
Leon.

Well...mine has a flat spot between 2nd and 3rd. But mostly because my rig is about 750lbs heavier (maybe more) than stock...plus a 1500lb trailer in tow. Let's just say 2nd get's used alot more now on those mountain grades/passes.




Christo: Any 1/2 price sales coming up on turbo installs?

 

[hoser]

For half price? Count me in too!

If you're transmission is excessively slipping between shifts, it could be on it's way out. What is excessive? Hard to say. Maybe the best thing to do is drive another 100. When's the last time the tranny fluid was changed? If you don't know, do a fluid exchange rather than flush.

 

[xlr8it]

It is not a transmission slip, the shifts are very firm and precise it is more like the engine drops power for a split second between the changes and the powers on again as per normal as if you took the foot of the accelerator. It does this between 1st and 2nd , 2nd and 3rd when i have the accelerator more than 3/4 way down.

 

[hoser]

Mine doesn't do anything like that. Does it feel like a misfire? Like one of the coil packs going out?

 

[xlr8it]

No it is not a misfire, it is hard to describe, it is just when it is accelerating hard from first and goes to change into second it feels like it runs out of fuel ,but it is just for a spilt second, which makes the shift very smooth, it does not feel like it is anything wrong because it is all so quick,I thought it might be done for that reason from the factory.

 

[hoser]

I'm not sure what you're feeling but just know that peak torque occurs at 3200 RPM. At 3/4 throttle, the engine is sure to rev past 3200 RPM and anything after that the engine may "feel" like it is not pulling as hard.

 

[Travis351]

My 99 does something similar but not exactly. I can really notice it when the overdrive is off and I am driving on flat roads with a load. Slight changes in accelerator position cause the engine RPM to behave opposite what they should instinctively. If I let off the gas slightly, RPMs go up slightly if I give a little more gas RPMs go down a little. No gear changes take place, feels like the torque converter protecting itself or getting confused, but is probably just the transmission control unit taking care of business.

 

[spressomon]

My 99 does something similar but not exactly. I can really notice it when the overdrive is off and I am driving on flat roads with a load. Slight changes in accelerator position cause the engine RPM to behave opposite what they should instinctively. If I let off the gas slightly, RPMs go up slightly if I give a little more gas RPMs go down a little. No gear changes take place, feels like the torque converter protecting itself or getting confused, but is probably just the transmission control unit taking care of business.

That is another observation I have made with mine. If, for instance, you are pulling up a grade and in 3rd with OD OFF and then switch OD ON the engine RPM's go up about 500rpm...must be the torque converter. It's like an effective 1/2 or 1/4 gear step.

 

[cary]

That is another observation I have made with mine. If, for instance, you are pulling up a grade and in 3rd with OD OFF and then switch OD ON the engine RPM's go up about 500rpm...must be the torque converter. It's like an effective 1/2 or 1/4 gear step.

I believe pre-2003 100's use the same tranny as the 1995-1997 80 series. If this is correct what you are observing is that when you shut off overdrive, the torque converter can lock up in 3rd gear increasing efficiency and decreasing the heat in the transmission. When you turn the overdrive back on on a hill that you are in 3rd gear, you are simply observing the effects of the converter unlocking. This is why when climbing long grades that you are in third gear it is a good idea to turn overdrive off.

 

[SINCITY100]

That is another observation I have made with mine. If, for instance, you are pulling up a grade and in 3rd with OD OFF and then switch OD ON the engine RPM's go up about 500rpm...must be the torque converter. It's like an effective 1/2 or 1/4 gear step.

Yep, I have always been curious of why this occurs when disengaging/engaging O/D in 3rd gear.. it seems to pull a bit better though, when the RPMs go up slightly in OD, so on steep climbs locked in 3rd I will switch the OD back on for a slight (percieved) increase in passing power.

As far as a drop in power between gear-shifts... I have a very noticeable "bog" when my 100 goes into the next gear..especially under heavy acceleration, but I assume that this is due to the increased tire size and the substantial weight (over stock) that I am running

 

[spressomon]

Yep, I have always been curious of why this occurs when disengaging/engaging O/D in 3rd gear.. it seems to pull a bit better though, when the RPMs go up slightly in OD, so on steep climbs locked in 3rd I will switch the OD back on for a slight (percieved) increase in passing power.

As far as a drop in power between gear-shifts... I have a very noticeable "bog" when my 100 goes into the next gear..especially under heavy acceleration, but I assume that this is due to the increased tire size and the substantial weight (over stock) that I am running The 4.88/35" help this overall but still not like stock due to the heavier/higher rolling resistance 35" MT/R's (plus all the extra weight the rig has gained (oooo....that turbo of Christo's sure sounds nice...except the $10K of course smarts)

 

[xlr8it]

"Bog" between gear changes under heavy acceleration is how I would describe it best. I do have some extra weight in it but I am running stock tires.

I am glad to see that I am not the only one with this "problem" ,so I can leave it alone and not worry about anymore.

 

[hkeller]

Hey. OUr 2000 does the same think. I think the engine revs too freely for this three speed tranny. It need another gear to absorbd the difference, if that makes sense.

H.

 

[Jim_Chow]

I haven't noticed anything like this in the 5speed. No overdrive, either.

 

[cary]

Hey. OUr 2000 does the same think. I think the engine revs too freely for this three speed tranny. It need another gear to absorbd the difference, if that makes sense.

H.

You better get your transmission checked then, because it should have 4 gears.