Shift problems related to ATF viscosity?
Hi Guys,
I have a 307 2.0L XSE AL4 robo-auto gearbox, 2006, 130k.The AL4 has been dodgy for some time and I have done many things to try to fix the problem. This is a common problem with this car. My mechanic now comes to me for advice! (which is sell the car quick, but mine has grown on me).
The gear changes are all good, except for when hot and coming to a stop. When hot, the box almost never drops back into 1st. It's either in a higher gear (at least 3rd) or neutral, I'm not sure which. When you go to accelerate away it slams into gear and the engine tries to climb out the front of the car (I've had to have engine mounts replaced).
I'm used to it and can feel when it hasn't dropped into 1st, so I either gently tweak the accelerator a couple of times (when on the flat) or manually put into into 2nd (when going uphill). It's now second nature to me, but anyone who borrows it, comes back in tears (the rolling backwards when stopped on a hill in commuter traffic is scary enough, but the slam into gear is the icing on the cake... or the PP on the seat).
What I have done:
1) I got a full flush and change done at about 90K (Lubemobile mobile mechanic. They say they do a full flush, but I'm not sure how, and then replace). That did significantly reduce the problem. I don't remember what the ATF was.
2) My mechanic replaced the ATF with Nulon at my request to see if that had an effect. The change was for good, but not permanent and since then I conclude it was the change, not the Nulon.
3) After years of diagnosis I determined that the problem only occurs when the transmission gets hot. In summer, as soon as the car thermostat hits 90 degC the problem kicks in. In winter it's less obvious, because the engine doesn't get hot, so the thermostat doesn't hit 90, but the transmission has been worked hard, so is clearly hot.
4) My mechanic suggested adding an intercooler to the transmission. The boxes have a tiny cooling exchanger. My conclusion is that they are designed for Europe, not Australia. However, it's not possible to do this without some serious mods. He chickened out at that stage.
5) He did replace two solenoids which are apparently known to cause a similar problem and did a full flush and change while at it. This had negligible affect. Probably what I would have expected from an ATF change.
6) Stayed away from the Peugeot dealer service. These guys are both expensive ("we recommend a full transmission rebuild in Melbourne at a cost of $3000 plus freight" and often incompetent. Good lead mechanics, but they are now "customer relations managers" and the "techs" are often apprentices. They last straw was when the "technician" offered to top up the windscreen fluid as I was picking it up and opened the hydraulic fluid with a watering can in his hand (I kid you not).
My conclusion is that the problem is fluid viscosity related. When the AL4 gets hot, it behaves badly.
Just changing the viscosity to a higher one to compensate is likely to cause other problems at lower temperature (any experience here?) which is why the OEMs a very strict about what ATF to use.
Some digging shows that the Penrite and most others like it have specs like this:
40 degC viscosity: 36 cSt
100 degC viscosity: 7.4 cSt
Viscosity Index: 178
Brookfield viscosity at -40: 13,000 cSt
So what I think I want is an ATF with the same 40 degC viscosity, but a higher 100 degC viscosity.
Mobil ATF 320 has a higher viscosity at 100 degC (8.2 cSt), but I cannot find it's 40 degC viscosity. The Brookfield viscosity at -40 is higher than the Penrite etc (17,900 vs 13,000), so I presume its 40 deg viscosity is also higher.
Any experience with Mobil ATF 320 in the AL4?
What about other ATFs?
Bob