well its been 8 years since Block91 posted so I'd expect that car's been sorted out. As to your issue, quite often when you get a happy meal of codes dealing with speed sensors etc, it may actually be an issue with the ABS controller board. The speed sensors feed the ABS which in turn feeds the TCU and ECU. bad data in, can throw all sorts of unrelated codes. The problem with ABS board is they develop cracks in the solder which can give intermittant fails, throwing codes, odd transmission behavior that then goes back to normal. Start by Googling Volvo ABS repair (Midwest ABS, Xemodex and Rocha-tek are three vendors who rebuild the ABS boards and have web content to describe symptoms). The other codes could be caused by wiring issues (grounds/connectors etc) so you may need to uplug stuff, clean the contacts, inspect for cracked connectors/loose connections etc. The P0500 says the speed sensor was out of range the P0734 says the speed sensor input did not match the rpm value expected - which could be slippage or bad input data from the speed sensor. The P0740 says the ECU didn't get a correct signal from the solenoid that controls the torque converter - could be a bad connection or bad solenoid. The MAF is unrelated to the tranny as that measures intake airflow for the fuel mix. MAF codes often get set as a result of a intake air leak - ie torn boot, vacuum line, exhaust leak etc. I'd start by reading up on ABS board symptoms, clean connections where possible, see if you can sort out the speed sensor. Also check the transmission fluid level and color via the dipstick. If its very dark and smells burnt, you will want to drain and possibly drop the pan/ filter the fluid to see if there's any debris (which would be bits of the clutch pack...). Have you been able to drive it enough to feel whether its slipping or not?

 

Jerry's 1998 is equipped with the 4 speed not the 5. The 5 speed came with the 2001.
The 4 speed needs only "Good 'Ol Dex/Merc", the cheapest ATF in the store.
New fluid may cure some of your ills.
Recheck for codes after the fluid is clean.

 

best thing to do is check the owners manual (https://www.volvocars.com/us/own/own...owners-manuals) when in doubt.

As George noted, Dex IIe/III / Mercon is appropriate for a 98 V70

 

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You may have both a transmission and ABS module problem. You can safely and cheaply do a flush with HAVOLINE 226536481-12pk Full Synthetic Multi-Vehicle ATF-1 Quart (Pack of 12). The other and I think newer packaging you'll find on Amazon has Dexron on the label but is on the back this also.
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Over a year ago I installed a transmission cooler bypassing the radiator on our 215K plus mile O3 Odyssey and a Transgo shift kit, flush and filter changed on the 03 S80 T6. Your XC should use a Dexron Fluid which I used for a 98 S70 T5 in 2012. The Havoline gave no trouble to either the 03 S80 nor Odyssey which is suppose to only work well Honda Fluids. It will also work for flushing your powersteering fluid. Do the flushing first, since it needs one, according to the video in this post and see if the codes go away.
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If not here is test for the ABS Module to see if the codes go away. I would not recommend and disagree with the writer of the article to use it as a permanent fix. Too much liability to yourself and potentially others but will work for diagnostics.
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https://www.carinstructions.com/volv...70-abs-module/
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