S90 2 years of shifting problem

vova · Post by **vova** » 19 Dec 2012, 20:01

I have been having this problem for almost 2 years. It started as once a week problem and now this is a daily issue.
transmission down shifts irrrrratically until speed reaches apprx 20 mph. There is no shifting problem coming to a full stop from highway speed. There is no problem driving above 20 mph, there is no CEL, no flashing arrow, no flashing WES, tranny fluid correct level slightly burnt, I went to a volvo dealer to scan TCM and there was no codes except for 114 (program selector switch) it was erased and it never came back also i was told that such code doesn't creat shifting problem. I also have been having small vacuum leak but it should not affect shifting as i was told my many reputable mechanics.
No shop here can pinpoint problem but everyone wants to replace transmission with no explanation.

thank you all

s90 161,000

Post by **jimmy57** » 19 Dec 2012, 23:18

I don't understand what "transmission down shifts irrrrratically until speed reaches apprx 20 mph" means. It shifts up and then downshifts repeatedly?

vova · Post by **vova** » 20 Dec 2012, 19:05

Thank you for your time, let me try to explain the best i can.

From the dead stop as i am gaining speed at around 10 mph RPMs dropps from 2000 to aprx 1000 and car goes into a lower gear for 1-2 sec giving a slight jerk and then right back into previous higher gear, sometimes it does twice before reaching a speed of apprx 20 mph. It seems like its hunting for 1-2 seconds. I dont know between what gears it does this but it feels like if it goes from 3 to 2 for (1-2) sec back to 3; 4 to 3 back to 4, so i guess once it is done shifting thru gears it drives just fine. When coming to a stop from highway speed it does smooth shifting all the way to a complete stop no jerking.
Another words as i am accelerating it shifts down and rpms go down as well briefly.

i can my mechanic exactly what it does but what i said above is somewhat clear.

thank you all

lummert · Post by **lummert** » 20 Dec 2012, 20:30

Maybe the engine speed is decreasing causing the trans to downshift. Maybe an intermittent engine electrical problem.

vova · Post by **vova** » 21 Dec 2012, 08:12

It hiccups. It down shifts for 1-2 sec. as i m accelerating. Once i am above 15-20 mph it drives just fine and there is never a shifting problem coming to a stop from highway speed. Is it possible for an engine to down shift transmission and not transmission to down shift itself? I had a small vacuum leak 2 years ago now i have a large vacuum leak, 2 years ago shifting problem once a week and now every day. Is this a coinsidence or not? I know that tranny is not operated by the vacuum but it does affect engine. new fuel filter, sparkplugs, air meter, timing belt. No CEL except for large vacuum leak that comes on every 100 miles after i clear it. No tranny codes, no flashing light on dash or by the shifter; car is in very good condition otherwise.

lummert · Post by **lummert** » 21 Dec 2012, 18:07

What is the cause of this large vacuum leak?

vova · Post by **vova** » 21 Dec 2012, 22:10

unknown. somewhere within charcoal canister and all related vacuum lines, gas tank cap. p0455

vova · Post by **vova** » 22 Dec 2012, 22:13

jimmy57 wrote:I don't understand what "transmission down shifts irrrrratically until speed reaches apprx 20 mph" means. It shifts up and then downshifts repeatedly?

Yes, as i am gradually accelearating it downshift with tachometer dropping to aprx 1000 rpms, it does it once or twice before i reach aprx. 20mph

Post by **jimmy57** » 24 Dec 2012, 23:14

If there is a short to ground in the wiring or a faulty switch then the TCM could be going into W mode and out again and make for some weird up and down shifts.

Pry out the mode selector switch. Locate the gray, gray/red, and black wires at pins 1, 2 , and 3. The black is ground and the gray and gray red are signals for S and E and also W modes. With key on gray and gray/red should have 5 V. If not, there is a wiring problem between the TCM and this connector. If voltage is OK then use a bent paper clip inserted between black and either of the grey or grey/red connections to put it in S or E and then go drive and see if the problem is there. If it is fine with the jumper in place then that would indicate switch problems.

vova · Post by **vova** » 25 Dec 2012, 12:36

Thanks

here is what i have:

key ON engine not running between 1 and 3 10V and between 2 and 3 10V
when engine running 1 and 3 12V, 2 and 3 12V.

How should i proceed from here?

thanks