'98 S90 Transmission Shifts, Has Fluid, No Codes, But Won't "go" In Any Gear!

[VolvoFan 28]

The car is a '98 S90 with the original AW-30 transmission and 130k miles. I got the car with just over 100k miles, so I don't know what maintenance was done to the transmission, if anything. I had the problem with the sticking gearshift lever, so I bypassed the key lockout by shimming the cable shortly after I purchased the car a year ago and had no problems since.

Over the past month or so, I've noticed a "whining" noise coming from the engine bay, almost like a motor's bearing was going bad. It grew more and more pronounced but the car still drove fine and shifted properly from what I could tell. Over the past couple weeks, when I first back the car out of the garage in the morning (slight down incline out of the garage), I go to shift from R to D and it didn't engage... just acted like it was in neutral. I had to put the car back into park, then back to D and it would finally decide to take off. I've had cars with automatic transmission issues before, and it was behaving like there was a loss of transmission fluid, so the first thing I checked was the fluid level. Everything was topped up to the proper level and there was ZERO leakage under the vehicle. A light coating of oily road grime over most of the undercarriage in the engine/transmission bay area, but not even so much as a DROP of tranny fluid on my garage floor.

When the car decided to not move after sitting for a week while we were on vacation, I decided to try a transmission flush to see if that would get things going again. Just to clarify... before I drained everything, with the car in a particular gear, I could get it to move a little bit if I revved the engine. I.e. in D, if I revved up to about 3,500 RPM, the car would crawl forward a few MPH so I could maneuver it about in the driveway/garage.

I drained the pan, then put the car in gear with the engine running and the parking brake on and a flush line attached to the oil cooler connection on the radiator per the procedure described in the 700/900 maintenance FAQ. This did NOT generate much tranny fluid coming out at all. I've flushed a transmission before and the fluid comes out at a pretty good clip... this just drizzled out. I couldn't add it very fast back to the transmission because I was doing so through a rather tiny hose, but it seems like I should have been getting MUCH more out of the oil cooler connection at a MUCH faster rate. What did come out was definitely brown and "gunky" looking. Didn't smell burnt, which is good, I suppose. There are no codes, flashing warnings or indicators, or anything of the sort coming from the car.

I would VERY much welcome your thoughts. My theory is that the oil is not getting from the pan into the "guts" of the transmission... hopefully just due to a clogged filter. I have a new filter and gasket on the way that will hopefully address the issue. You will notice multiple uses of the term "hopefully." I do not relish the thought of dropping this transmission to try and find/free a stuck valve or something like that.

Thanks in advance for any help or suggestions you can provide!

Best,

-Jon

[Three Fat Tigers 25]

It sounds like the main pressure pump is gone, failure to routinely change the fluid was the most likely cause. There is a line pressure test port on the left side that you can connect an pressure gauge to test this, but your trans cooler line test and other symptoms pretty much prove it. Although a clogged filter can cause both the whine and loss of pressure, but this would be a very rare condition, should be easy to check once you drop the pan. Cost of repairing a failed pump would most likely far exceed replacement with a working used unit, Volvo specifies replacing the entire transmission.

If you do replace it, I suggest saving the PNP switch, the internally mounted electric solenoids, and maybe the torque converter for spares.