1988 740 Turbo with Manual Transmission-3rd Gear problem

[TurningWorm]

I have a 1988 740 Turbo Wagon with a manual transmission. I have owned various 240 and 740 series cars over the years and I am pretty familiar with the quirks and gotchas of the automatics, but this is the first manual I have ever messed with. For the most part it runs pretty well, but there are two issues I'd like some advice on. I'm hoping there's someone on here with some more experience with these things.

The first is that when I engage the overdrive it seems to shift pretty hard. There's a big "chunk" as it goes into gear. It works fine, it's just not a very smooth transmission.

The second thing is that occasionally while in third gear it will seem to change gear ratios randomly if that makes any sense. It never comes out of gear, it just changes speeds. I've had problems like this with automatics before, but not a manual. It doesn't seem to make sense. It's almost like the overdrive was trying to engage from third or something.

Anyone have any sage wisdom to impart? Or is my transmission just hosed?

[billofdurham]

How long is it since the transmission fluid was changed? For some reason Volvo did not make this a service item but all oil wears out eventually. The overdrive relies on the oil pressure to engage/disengage the overdrive and old oil may not be able to give that pressure.

Check the level and condition of the oil which should be type F or G automatic transmission fluid. Any doubts about it, change it. Some books advise changing the oil to Redline MTL which is a synthetic. That choice is yours.

740T M46 transmission service..pdf

(166.13 KiB) Downloaded 186 times

Start with this and let us know what you find.

Bill.