Gearbox funny

[deanosabby]

Hi Forum,

I had an odd one this morning with the XC.
Normally the car sits at 2000rpm in 6th gear at 70 mph.
This morning it was sitting at 2500rpm in 6th at 60mph. This has happen once before but didn't really think anything of it. Once the car was warmed up all was back to normal.
I have got the car booked in on the 18th to get an gearbox oil change and to see if there are any software updates needed.
It is a D3 5cyl 2.0 with an auto box.
Has anyone else had this happen before?
Ta,
Deano.

[kenny]

The torque converter will slip at higher revs when cold on the 6 speed boxes.
As long as it locks ok when warm it should be fine.

[Clan]

Originally Posted by deanosabby

Hi Forum,

I had an odd one this morning with the XC.
Normally the car sits at 2000rpm in 6th gear at 70 mph.
This morning it was sitting at 2500rpm in 6th at 60mph. This has happen once before but didn't really think anything of it. Once the car was warmed up all was back to normal.
I have got the car booked in on the 18th to get an gearbox oil change and to see if there are any software updates needed.
It is a D3 5cyl 2.0 with an auto box.
Has anyone else had this happen before?
Ta,
Deano.

You were probably going up a slight incline when the torque converter lock up clutch lets go , they you get slight slip in the torque converter until you go back on the flat and let your foot up a fraction ( which you do not realise ) where it will lock up again .

[Model flyer]

As Clan says the torque converter clutch will slip if on incline etc but should lock up at about 50 to 55 mph. If your towing and it slips while on a long incline its worth changing down manually and locking it in a lower gear . Doing this will prevent overheating or any damage to the gearbox.

[RM955I]

Mine does this - generally in 3rd (I think), more noticeable when cold. As said, quite normal from what I can tell.

[Simon Jones]

Most autos will delay going into top gear / lock up when cold to aid a faster warm up of the engine and gearbox.

[Tatsfield]

While Simon has an interesting point, it is also possible that there is a viscosity problem with the ATF when it gets hot. Perhaps changing the ATF would sort out this feature or at least let the transmission ECU make decisions about warming up the engine without dying ATF influencing the outcome.

[Tannaton]

It is normal behavior - when cold the TCM will change the parameters which means the gearbox will hold on to gears for longer and delay locking up the torque converter. All AISIN WARNER Volvo Geartronic boxes do this - it's to speed up the warm up cycle of the catalyst and transmission oil.

Volvo do not include gearbox oil changes in their service schedule but recommend changes at 36k intervals for heavy use vehicles (taxi, hot climate etc.) most if not all of the experienced mechanics on here would suggest changes around every 72k for domestic use vehicles, more often if towing a lot.

[JDmac]

Any ATF recommendations Guys? Cheers,JDmac.

[apersson850]

Living in Sweden, I'm exposed to more cold weather than most of you. I can confirm that when it's freezing outside, there's no difference in the gear change points, but the gear box doesn't apply any lock-up until it has reached a certain oil temperature.

When lock-up isn't engaged, the engine will run a bit faster, since the torque converter downshifts hydraulically, and in the process there's some slip as well. The hydraulic downshift depends on the load, which is why the engine will run faster uphill than downhill, even if the car's speed and the selected gear is the same.

The same kind of hydraulic downshift may occur when driving up-hill, especially when towing heavier trailers. This is normal with torque converter gear boxes, and is one of the reasons for the torque converter to be there at all. You hear it by its name: Torque converter. You can design automatic gearboxes with hydraulic clutches without torque converters. They are usually more efficient, thus not so much in need for any lock-up. But they'll never multiply the incoming torque with a value higher than one.
I don't have the data for the torque converter in the AW TF-80SC used by Volvo, but typically such torque converters can increase the torque by around 50 %. The drawback is loss of efficiency. You can make such torque converters reaching figures of about 100 % increased torque, i.e. doubling it, but then the efficiency penalty is larger.
Overheating the gearbox is hardly any issue today, as the oil is cooled by the engine coolant through a heat-exchanger, thus operational even at very slow speeds. The temperature is also monitored by the gearbox.

I replaced the oil in my gearbox after 120000 km. It made a significant improvement on gear shift quality. Hopefully on gearbox lifetime too.