I have an 850 Turbo with auto transmission that has an intermittent problem shifting into 4th gear. This happened once before back in August of 2007 and now happened again.

I was driving on a really hot day and regardless of vehicle speed or engine RPMs the car would not shift from 3rd to 4th. I tried activating "Winter Mode" to see if that would push the transmission into 4th, but it would not. I also stopped and turned off the car then cranked the car and drove again but it would still not shift into 4th gear. When I got home I let the car cool off for 3 hours then did a test drive and then it would shift properly into 4th gear.

I checked for transmission codes from the A1 socket and there were no codes (just 1-1-1).

The transmission fluid has been replaced every 25K miles and still looks clean and is at the proper level.

Any ideas?


Thanks!

 

The transmission module may be bad.

Worst case scenario is that your transmission may be bad. I haven't really seen many 850 trans' going bad.

 

Transmission is oil cooled. Any oil leakage around transmission?

 

No transmission fluid leaks at all....

Does anyone know if the Shift Solenoids S1, S2 could be the problem?

FCP Groton sells them and states "Upgrade your vehicle's transmission by replacing your Shift Solenoids today! Shift solenoids are the devices in your vehicle that allow, or prevent, hydraulic pressure, which ultimately holds your vehicle's selected gear in place. The different combinations in which the two shift solenoids allow fluid to pass through determine what gear sets you car runs in. When you feel as though your car isn't properly shifting into the right gear, it probably means that your shift solenoid is bad, and it is probably time to replace this part with a new one."

Do you think I should try replacing these S1 and S2 Solenoids?

Thanks!

 

I found a Transmission computer for my car on ebay for $30 delivered... so I bought it since it was so cheap. I'll report back in a week or so after I receive it to let you know if the new computer helped or not. By the way, the tranny has been acting fine for the past 3 days under normal driving conditions.

I'd rather not replace the solenoids since the it will take me several hours for the swap out plus cost about $110. But if anyone thinks the solenoids are probably causing the issue I'd appreciate the info...

Thanks!

 

Hi, my '94 850T just starting having a very similar problem today... how did you resolve your problem? Shift solenoid, trans module... or something else? Thanks

 

I did change out the transmission module back in July of 2009 right after having the shift problem. The car drove fine afterwards until once last summer on one instance only, again on a really hot 95 deg F + day when I did a lot of back to back short trips. After letting the car cool for a few hours, the transmission shifted properly again. After last summer's issue, I changed the transmission fluid.

I drive this 850 Turbo every day to work and it hasn't had any other transmission issues. I know it will do it again if I do short trips back to back on a super hot day... and I'm still considering changing the shift solenoids.

So, in my case, the transmission module was not the solution. My best guess is the solenoid valves since I have no fluid leaks and my transmission fluid has been changed regularly and is in good shape.

The thing shifts perfectly every day of the year, except those few really hot days when I drive 5 miles, stop the car, then within 2 minutes get back in and drive another 5 miles, stop the car for a few min, then drive some more. Perhaps I should simply stop driving little short trips consecutively like that on really hot days!

In your case, after your car cools down, did your transmission return to normal shifting?

 

I did a little more googling and came across this:
i have a 1995 volvo 850 turbo and transmission ... - JustAnswer

According to this, the symptoms for a bad S2 solenoid is, "poor performance due to the transmission operating in 3rd or 4th gears or operating only in 4th gear." My problem is just the opposite, I can't shift into 4th gear. This adds more doubt to the S2 solenoid being the culprit for my specific issue.