Engine: 2.5: baffled by surge

[jack taylor]

Hi, I have a 1998 V70,2.5, 20v auto, non turbo. I always drive with gearbox in "economy" mode. At 50mph I lift off the accelerator slightly and the car changes gear or overdrive kicks in; I dont know which, and revs drop from 2,000 rpm to 1,750 rpm. Today no sooner had revs dropped they surged up to 2250rpm and then back down to 1750. This happens constantly all the time I am at 50mph and revs will surge and drop in less than a second. 80kpm is max limit on many roads in my area so I cant just drive faster.I would compare it to a manual box with a slipping clutch. Once I reach 55 to 60 mph the car is fine.
I changed the gearbox setting to "Sport" mode and the problem seems to have gone.Do I have a massive gearbox problem or something totally unrelated. I would very much appreciate your views please. thanks jack

[Dippydog]

I'm not sure how Volvo auto boxes are configured,but some autos on a stedy cruise hit torque converter lock up at about 50mph so if you're driving at this speed and lifting off the throttle slightly the gearbox can't make up its mind whether it should be locked up or not so it's sort of "hunting" between gears if that makes sense.Engaging sport mode cures this because in sport it holds each gear to a higher rev speed before changing up.It sounds pretty normal to me but maybe others know differently/better.

[DSK]

Sounds like your are doing this type of driving all that should be consistent.

If you have always had the above issue, I'd tend to agree with the above but obviously you will want to check the basics such as a full fluid change of the automatic transmission and if there are any software updates for the trans,ission that you may be missing.

If this is something that's just started happening? (if so, then the problem will be elsewhere).

[jack taylor]

Hi Guys, Thanks very much for the info. This problem only started yesterday.The gearbox fluid is clean and full. Assuming the problem is gearbox related does it sound terminal.many thanks.

[jack taylor]

I have read articles relating to "torque lock-up solenoid". Would anyone know whether this is a part fitted to Volvos.

[jack taylor]

Apologies for being a pain but may I ask whether my gearbox problem could be a faulty TCU. Thanks

[SwissXC90]

Originally Posted by jack taylor

Apologies for being a pain but may I ask whether my gearbox problem could be a faulty TCU. Thanks

Unlikely. Start with fluid and torque converter.

[jack taylor]

Hi, SwissXC90,Many thanks for that. The fluid level is full and the oil is clean. Forgive my ignorance but what steps can I take to check the torque converter.
When i select "sports" mode the problem stops so I thought it was an electrical problem. thanks jack.

[Baffler]

Jack...have you seen/read Capt Jack's thread - Automatic gearboxes at 50mph - in General Volvo Motoring Discussions? Makes for interesting reading as your car may be perfectly fine.

I can't comment further on the AW50 (4 speed) as we only bought ours last July and it's at our place in Poland so don't get to use it as much as we'd like. Although, it drove faultlessly for 2k kilometers across Europe, I'll keep a note of it's behavior this summer.

[jack taylor]

Hi Liam, Good to hear from you and thanks for directing me to Cpt Jacks post. What concerns me is the fact that my g/box has been faultless for the last 7 years and has only just decided to bugger about in the last week. There must be a fault; its trying to ascertain what it is.
I dont think its mechanical which only leaves electrical and in that regard, I havent a clue. Perhaps someone on here can throw out a few suggestions.jack