Automatic gearboxes at 50mph

[capt jack]

Now I much prefer driving an automatic, and have done so for 20+ years now.

One thing I have noticed is that autos often don't sit very happily when the traffic is bumbling along at between 45 and 55 mph. You know the sort of Sunday traffic where you can never really get going before you find yourself up behind the next lost soul who insists at meandering along at 49-ish.

Under these conditions I've found that the S70 and now my '98 S90 can never really settle into a gear, and the slightest pressure on the throttle pedal will prompt a down-shift, whereas letting the gas off a touch wins you an unnecessary up-shift.

It's less pronounced when using the S-mode.

I've always assumed that there's an up-shift point programmed at around 50 mph, and a downshift maybe a little higher. In trying to keep to a road speed within that range, especially if the road is pretty much flat, the gearbox simply keeps getting mixed messages about the load and the road speed. In S-mode of course the gearbox is programmed to hold on to lower gears for longer, so the effect is less noticeable.

Has anyone else ever found this? Apart from selecting 3rd (assuming it's a 4-speed box), have you ever worked out a trick for smoothing things out?

I did try one of those clutchless manual beasts (in a Honda Civic) that had something called I-Shift technology, which I quickly came to re-christen I-****. After several unsuccessful software re-boots the dealer agreed to take the car back as unrepairable. I don't know if other manufacturers clutchless manual systems are as bad, but that Honda was a potential death-trap. On more than one occasion pulling away in traffic, the damn thing floundered for a gear and then usually selected 4th or 5th, making joining faster-moving roundabouts a particularly hazardous adventure!

Cheers

Jack

[Prufrock]

What you describe sounds like a fault, I have two 740 autos - have had 960s also, and my two classic Mercedes and my daily drivers are all automatics. Can't say I've experienced what you describe unless there's been a fault or maladjustment somewhere - kick down cable ?

Had what I thought was a fault on my BMW 728 (had three 7s in a row), it wasn't changing into top gear...a change of fluid did the trick !

Jon.

[capt jack]

That's interesting - you've got me thinking now. I can definitely remember that my old V70 was like this, and a friend who had a Ford Granada came up with the theory about the gearbox becoming confused by minor changes in foot pedal pressure, so he'd noticed it too.

Wonder if it's down to driving style?

That's a perfect excuse for a bit of an evening drive!

Back in an hour or two!

Jack

[Dippydog]

Someone else has posted a similar question on the model specific board[P2 V70 etc]thelast auto Volvo I had was a 245 back in the mid '80's so can't recall what that was like,but the 2 Senator B's an X300 Jag and 2 Omega 3L I've had with 4 speed boxes have all tended to do this.At about 50mph it goes into torque converter lock up[I believe]so if you're travelling around that speed the gearbox gets "confused" as to whether it should be locked up or not so "hunts between the two states.Putting it in Sport delays gear changing in the rev range so lock up won't occur until later in the speed range.Can't do links to other thread but look for "Baffled by surge" for other answers{?}

[DaveNP]

I noticed a similar thing in a Nisan Micra which I had as a hire car at work, the speed was a little higher as I recall but just the same, as I tried to go with the flow on the motorway the box was flicking up and down in an irritating manner.

[Dippydog]

Apologies, the thread I referred to in my earlier post is in fact in the P1 V70 etc section and was originally posted by jack taylor.Sorry for the confusion.

[MikeGMT]

Sounds like it's 'hunting' between the two ratios, a common trait with autos. I don't know the transmission type concerned or the layout and options available on your S90. Prior to my current car (auto.) my only experience with auto transmissions was with 3 speed and they didn't have the electronic 'brains' todays cars are endowed with. I had a long spell with manuals and now back in a auto; as you will appreciate things have moved on bit since then.

Assuming that the 'box' is working fine, and no faults, sometimes you have to think 'manual', and override it's decisions, show it who's the boss. In the scenario you have mentioned in a manual box you would take the appropriate gear for the circumstances, based on what you can see, with the auto it can only go by what your right foot is doing, so you are driving along at a steady state, the car has selected the right gear and as you close on the car ahead you ease off the throttle and a change occurs, then as the gap opens you get back on the the gas and another change occurs and so on.

I think you have answered your own question really, it's all down to driving style and take more control of the box when it starts being indecisive.

Have fun Jack with your new car learning all its characteristics.

[capt jack]

Thanks all. Fascinating replies - as ever on this, the best car forum on t’internet! Just been for a 15 mile drive, then checked the auto box fluid. The fluid is clear and pink and spot on the Hot line of the dipstick, so I’m happy with that.

Interesting that others have had or at least heard of similar experiences. All things considered I’d sooner have an auto, and a proper one at that. I’ll learn to drive around this!

The other factor in this is of course the age of my S90, it’s over 20 years old. The S70 is a bit younger, but has done over 200k. My old V70 was a 97, and that had done 300k, so I guess some allowance has to made for age and mileage!

The evening drive has however made me aware of another issue! I drove (slowly) over some speed bumps in town, and heard some rather alarming rubbery squealing and squeaking. Getting back home I had a good look around the front end. I reckon the noise is coming from where the lower wishbones are attached to the chassis. Someone has smeared a thick red grease around the rubber bushes, so presumably it’s been an issue before. There are no clonks or knocks from the suspension, just this squeaking noise. Is this a new wishbones job, or are the rubber bushes a replaceable item I wonder?

I guess that I’m seeing this sort of issue because I’m using the car rather more than did the first owner. He did 90k in 21 years, so 4K a year. I’ve driven 2k in 2 months, so I suppose a few things are bound to crop up.

Thanks again for all the comments

Cheers

Jack

[Martin Cox]

I have a 1998 Ph1 V70 Tdi auto with the 4 speed automatic transmission and i know just what you mean. Although by 40 mph it's usually in 4th gear, the torque converter won't lock up until just over 50 mph and this feels like an extra gear change accompanied by a slight drop in revs. it will then stay locked up until the speed drops too low or you touch the brakes. It's frustrating if you can't get over 50 where legal for long enough lock-up to occur.

I also have a 2008 Ph3 V70 2.4D with the 6 speed Geartronic box and I have to say on balance I prefer the older box but this could be that I've driven the older car much further.

The 4 speed does what I want it to whereas the 6 speed seems to overthink things sometimes. I havn't yet quite worked out what the geartronic box is doing at about 50 but I suspect it too is dropping in an out of torque converter lock-up.

[Martin Cox]

In New Zealand I drove my daughter's Honda Fit, (1300cc petrol automatic CVT) and found it absolutely superb; one of the best automatics I'd driven. The Nissan version on her other car was rather less convincing.

The prize for worst automatic I'd ever driven has to go to a 1980 Volvo 240DL (B21A engine and BW55 3 speed transmission) that belonged to my Dad. He'd traded in a nice 1977 264 GLE auto against this horror thinking it would be more economical. It wasn't. It was gutless, thirsty and stalled at the slightest mis-manipulation of the choke. The connection between the accelerator pedal and the road wheels might as well have been by second class post. After 6 weeks he bought another 264 GLE Auto and kept it forever and a day.

With only three speeds and no torque converter lock-up there weren't many gears to hunt between at awkward speeds.