4hp20 second gear

[teo]

Hi,
can you see some problem while the second gear swings down then up for about 100-200rpm while accelerating?
See the video

around 2 500 rpm there is a temporary rpm drop.

Thank you

[ekjdm14]

Welcome, it's hard to tell from the video but it's possible it may be slipping slightly. As long as it generally goes into gear OK within a second or so of selecting R or D with no harshness I'd say its likely to be OK. A fluid change wouldn't do it any harm though, usually you need to do 3 or 4 changes in quick succession to get most of the old oil out of the torque convertor.

[Mandrake]

Is the car new to you ? What mileage is it ? If you have had it for a while has it always done this or has it got worse recently ?

Could you record a better video where you are accelerating at a moderate pace from a standstill to at least 80km ? Also your sound is very muffled and underwater sounding, so it's hard to judge without good sound.

However it looks to me like the torque converter lockup is a bit abrupt in 2nd gear. As you accelerate through 1st and 2nd the torque converter will initially be open (unlocked) which allows the RPM to climb higher to produce more torque, as the road speed increases the gearbox should smoothly transition the torque converter from open to closed - when this happens either the RPM will drop for the same road speed, or the road speed will increase for the same RPM, or a bit of both. Which you get depends on how hard you are accelerating.

Sometimes the transition from unlocked to locked can be very abrupt and cause a sudden drop in RPM and you will notice this most in 2nd gear, especially if you accelerate long enough to linger in 2nd for a while. I've had two Xantia V6's with 4HP20's and they have both behaved like this, although not quite to the same degree as yours.

It could be a sign that it needs an oil change or two, or possibly that someone has done oil changes with the wrong grade of oil with the wrong frictional characteristics for the box. It might also be a sign of sticking solenoids, low oil pressure, low oil level, or a worn out lock up clutch in the torque converter.

You could try doing a couple of oil changes (use only Mobil LT71141) spaced a few hundred miles of driving apart. If you have a Lexia you could also try doing an "Autoadaptive Reset" in the New Parts section of the software, and then go for a 10km test drive. This reinitialises the auto-adaptive routines in the gearbox and tells it to relearn the mechanical characteristics of the box. This may help.

At the end of the day I think once they reach a high mileage the occasional abrupt drop in RPM when accelerating in 2nd due to the torque converter locking up too abruptly is something that you're just going to see. After two of them now I just accept it as one of the quirks of a high mileage 4HP20. As long as it isn't really abrupt and the gearbox seems to be working OK otherwise, (no jolts or bangs when changing gears or RPM flare up when you touch the accelerator) and you have changed the oil I wouldn't worry too much about it. If there is a more deep seated cause there won't be anything you can do about it anyway.

Edit: Just noticed on your video your car has done 228,235 kilometres, or 142,646 miles. That is pretty high mileage for a 4HP20! They usually tend to die well before then, unless previous owners have done oil changes on the box. My first 4HP20 died at 111,000 miles...

[teo]

I am sorry I didn't get any email notice about your answers or it is at spam folder so I am coming back so later. Thanks for your opinions.
Car has now 2 500 miles more and no change. Same behaviour. Otherewise drives fine and smooth. Seemingly?
Expensive oil change was done when I bought the car 2 years ago (~141k miles) to minimalise the risk then later I got info that 110k miles and 10 years lifespan is considered as pretty durable geardbox just no experience with automatic gearboxes.
The exchange was done by complete flush with cleaning fluid going in reverse direction throug filter. The machine is called BG PF5. You know probably.
https://www.bgprod.com/catalog/transmis ... ge-system/
old oil claimed looking as original, never changed however in not so bad condition. The new oil was used Petro-Canada DURA-DRIVE MV SYNTHETIC red color. I heard later it's a death sentence to not use the original Mobil oil but serviceman made me sure about good experience with PetroCanada oils.
Now car is used in urban traffic mainly so changing gears really fequently.

To the problem: I have found this video

Diesel but
at 1m05s there is normal RPM drop as it goes from 1st to 2nd , then at 1m07s comes lock probably later than should and makes the abnormal tiny rpm drop. At 4:42 again tiny RPM drop while speedometer keep climibing steadily.
almost same meleage as mine.
I will try to make new video to see difference of slight and hard acceleration.

When tiny RPM drop occurs it's still very smooth. No bounce. No harshness.

I got one notice saying it's usual ware of old 4hp20 , going to be worse but can work long time still.
I am trying to pause acceleration for 2 seconds when I feel lockup of 2nd gear should come and it works.
When I do fullpower run I got the drop higher for example above 4000rpm.
Doing at manual mode same way.
Interesting behaviour is when riging fsteadily on 3rd gear and then accelarate suddenly to overtake I feel it puts there second gear smoothly, feel like immediate lockup and no rmp drop! I mean that tiny one drop. So only case I see the problem is when going from 1st do 2nd. Not from 3rd to 2nd.

Autoadaptive Reset is interesting option to try. But owner of lexia who can do it for me doesn't know anything about gearboxes. Others full or crazily expensive.
Just I'm currious if I'm facing RIP of car or not but i handled few thousands miles without change so it seems be not so critical.

Regarsd T

[teo]

Oil level checked few months ago. Red, light color, no burned smell. Good level.
Unfortunatelly I don't remeber it the problem was there prior oil exchange :/

[xantia_v6]

If the oil is red, then it is 100% sure that the transmission has been filled with the wrong kind of oil. The correct oil is clear and goes grey, then black when it is old.

[teo]

Someone (ZF) says wrong ... someone says good ... it's a PetroCanada oil for automatic gerboxes

[Mandrake]

If the oil is red, then it is 100% sure that the transmission has been filled with the wrong kind of oil. The correct oil is clear and goes grey, then black when it is old.

New LT71141 is actually a translucent yellow colour and changes gradually to black as it gets contaminated and/or burnt. I've never seen it clear or grey, and I would think grey could only result from particles of aluminium alloy which would not be a good sign... See my picture below where the far right test tube is brand new oil and the others are what drained out of the gearbox of my first Xantia V6 on each successive oil change:

I agree though that if the oil in there is red its the wrong stuff.

Someone (ZF) says wrong ... someone says good ... it's a PetroCanada oil for automatic gerboxes

You do realise that ZF made the gearbox right ? Why would ZF be wrong and some random oil company be right about whether their oil is compatible ? I would think that oil companies have a vested interest in claiming their oils are compatible with as many gearboxes as possible to sell as much as possible. Without looking at a very detailed specification of the oil you can only take their word for it.

The 4HP20 and other gearboxes that use LT71141 are well known to not last when using more generic Dexron grade oils - the oils are NOT the same, and have different frictional characteristics due to a different friction modifier package. If you use a standard Dexron II/III oil (which is usually red) in a 4HP20 it will cause harsh/abrupt clutch engagement which will cause rough shifts and other erratic behaviour and eventually cause damage to the gearbox.

[teo]

Interesting picture Mandrake. So we are going to see here how more milleage can handle 140k miles old 4HP20 on Petro-Canada DURA-DRIVE MV SYNTHETIC. Keep in mind that it was not usual oil drain & refill & repeated few times. It was complete flush&clean with BG machine. I will be checking oil every few months. Rough shifts I can recognize immediatelly but as I said the box have done on this oil 2,5k miles at mostly urban drive and still is quiet and goes very smoothly. Only that tiny RPM drop on 2nd gear....

[ekjdm14]

Well, that's one way of doing it I suppose... I can almost see your point, in that it's (probably, but not definitely... it could already have been rebuilt a few k miles ago?) an elderly 'box and the damage may be done but even so I think I'd rather see how long it lasts with the proper oil in it. I'd wager a good used/reconditioned 4HP20 costs more than a few litres of LT.

[teo]

No.. the car had really minimal maintenace/investments by previous owner. The OIL type was not my choice but choice of local service expert and importer of BG products. Surely not expert for 4HP20 but obviously had "some" experience with the box.

[Hell Razor5543]

I think it could be safe to say that the 4HP20 gearbox is 'allergic' to anything but LT71141 transmission fluid.

[teo]

Call out serviceman: Petro-Canada DURA-DRIVE MV SYNTHETIC has been used.
Tech Info: http://lubricants.petro-canada.com/Api/ ... lang=en-EN
If I knew I would ask for Esso LT71141 but now I see it works for few months ... so I won't mix the oils in my garage by partial exchange.

[teo]

Back to the topic:
Manual mode - RPM drop at 00:05 from ~ 2200 to 2000

Auto mode - RPM drop at 00:09 from ~ 2900 to 2800


Does or doesn't abybody observe the same? What mileage about?

[Mandrake]

The sound quality of your recording is really bad, however as I was saying earlier, it is normal to see a small drop in RPM in 2nd gear when the torque converter locks up, especially if you linger in the gear for a while.

Normally this drop is a smooth transition which takes place over a couple of seconds as the torque converter clutch progressively locks up. However if there is a problem it can be sudden so you see a sudden drop in rpm. I had this issue on my old Xantia V6 which had done about 100k miles.

I can think of many possible causes though including:

* Worn out lockup clutch on the torque converter, perhaps down to the metal. (Think of worn out brake pads that are worn to the metal - they won't brake smoothly and progressively but will dig in)
* Old/dirty/contaminated oil, especially if contaminated with metallic particles, this will affect the frictional characteristic of the torque converter lockup clutch.
* Wrong grade of oil with the wrong friction modifier package (eg Dexron II/III instead of LT71141)
* Sticking electrovalve in the valve body which controls torque converter lockup, which could be a result of dirty or contaminated oil, especially metallic particles
* Poor rail pressure regulation - which could be due to sticking electrovalves, blocked oil filter, or faulty pump.

So there are a lot of things that could cause your problem, most of which are not feasibly repairable. However really dirty or incorrect grade oil could also cause it so if I were in your situation where you know the wrong oil is in the gearbox, I would do some oil changes with the correct oil and see what happens.

However as long as there are no other symptoms and no funny noises when the torque converter locks up and the rpm drops I would probably not worry about it and just keep driving the car... I get the impression that all 4HP20's when they start to wear out tend towards a more abrupt torque converter lockup as it is such a fine balancing act to have a smooth transition, but that doesn't necessarily mean the box will fail or give you any real problems. It just won't be as smooth as when it was new.