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In the absence of Cephis to answer the questions about fluid changes ,etc, I can help fill in some of the details on what work has already been done and further info on the Syncro issues. Vehicle in question is a 1989 740 Turbo sedan, M46 manual transmission (overdrive is functional), with aprox 260,000 miles.
Last month, we changed the manual-trans fluid with some generic Type-F. Unfortunately, the fill plug on the M-46 transmission was completely rounded off (by a previous owner). Someone had done some real damage to it with vice grips and removed much of the metal from the plug head. We were unable to remove it with vice grips or a metal biting socket (the kind that they're selling at Sears and Autozone). I stopped short of pulling out the torch because time was an issue and the car had to be back on the road (and it was about 10'F with 2 inches of snow in my driveway). We were able to drain the old fluid from the drain plug, and then refill the transmission using a hand pump, tubing, and a foam stopper. The specs called for 2.5 quarts of Type F, and as a precaution we attempted to put in 3 quarts. By the time we were finished, we had spilled about 0.25 quarts and about 2.75 remained in the transmission as planned. The magnet (in the drain plug) was cleaned and about 1 to 2 grams of metal shavings were removed from it. The current plan is that another fluid change would be performed in 500 or 1,000 miles using Amsoil Racing Transmission Type F fluid, after the cheap Type F has had a chance to wash out the last of the old fluid. Also, the OD pan cover would be pulled at this time and the magnet and filter cleaned at that time. After re-reading Paul Grimshaws website on synchronizers, another fluid change with Amsoil should probably be done sooner rather than later.
Quote from Paul Grimshaw: "If your Volvo shifts cleanly except for 1st gear and reverse, the gearbox may be filled with fluid of marginal quality. Flushing your transmission with most "over-the-counter" fluids will not solve your gearbox woes. What you need is a fluid which offers higher viscosity stability. Synthetic fluids are specifically engineered to provide a much higher degree of stability than their conventional counterparts..."
During a couple of test drives (before and after the fluid change) I observed the 1st gear syncro to be non-functional. With the engine at idle speed, the shifter had to be thrown very quickly into first to keep the gears from grinding. Any attempts at shifting into first with the vehicle in motion would result in horrific grinding sounds, similar to those if you had failed to use the clutch. I would assume that the Syncro is stuck fast, and if any of you have any suggestions or opinions on fixing the problem, they would be greatly appreciated.
Other issues noticed while driving: The shifter does not stay in 2nd gear for more than 20 or 30 seconds of driving (uphill, constant speed, coasting, etc). It slowly works it way out of gear and back into the neutral position, -resulting in a sudden rev of the engine if you're not paying attention. You must physically hold the shifter in 2nd gear if you want to stay in 2nd gear while driving. The reverse gear requires a quick throw about 30% of the time to avoid grinding the gears (see quote above). Lastly, the transmission mount is bad and needs to be replaced very soon (based on visual inspection and pushing/pulling on the transmission sideways). It seems as if the entire shifter and trans moves forwards and up about 2 inches when shifting from 1st into 2nd gear (just as you release the clutch and engage 2nd gear). It probably would be a good idea to replace the engine mounts at the same time.
God bless,
Fitz Fitzgerald.
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'87 Blue 245, NA 230K
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