740 High RPM in overdrive

Hey all,

I got my first car, a (currently) Automatic 1992 Volvo 740 Wagon (non turbo). So far things have been great. The timing belt popped the day after I got it (On an interstate highway, no less), but I had it up and running again for the grand cost of $14. Other than that, it hasn't had any major issues.

I have noticed, however, that when I commute to work on the highway, the car runs anywhere from 2800RPM to 3500RPM. I can clearly hear the engine running as though it's searching for a higher gear that isn't there.

From what I read online, this sounds very much like an issue with the overdrive system. I can hear the relay click when I hit the button however, and the OD light is not on in the dash unless I hit the button.

However, I don't think it has to do with overdrive. I say this because, this morning on my way to work I waited until I was going highway speed (about 65mph) and then hit the OD button. The RPM shot up even higher and the sound did as well obviously. I quickly reengaged it and felt the 4th gear catch and the RPM's lower to around 3,000.

Any idea what might be causing this? I'm pretty sure it's the reason my gas mileage is awful (I can't give an exact number because unfortunately the speedo is not working, although I plan to fix that this week). If I had to guess I think I'm sitting around 12-15mpg (I do 30 miles a day of highway driving).

Any ideas would be appreciated.

The overdrive button is for locking out overdrive for towing or driving on mountainous roads.

What you're describing is normal for these cars. Remember, back when these vehicles were new, 55MPH was the norm. So 60-80MPH now(depending on State) is going to make it sound rapped out.
Adding off of what lummert stated above; if it kicks out of OD and into 3rd when you click the button on the shifter and the indicator light turns on and then turns off, goes back into OD when pressed again; your transmission is functioning properly.
The MPG is a bit low. Get to "Stage 0": complete tune up(spark plugs, plug wires, cap, rotor, air filter), any bushings(if needed), motor/tranny mounts, oil change, transmission fluid change, rear differential fluid change, inspect(replace if needed)coolant, clean AMM, throttle body and IAC valve and inspect brakes, inspection/adjustment of kickdown cable.

lummert said:

The overdrive button is for locking out overdrive for towing or driving on mountainous roads.

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I understand this, as the button kicks the transmission out of the "overdrive" 4th gear. As I understand it, when the car is doing highway speeds, it should be in overdrive and the RPM shouldn't be as high as it is on my wagon.

That MPG sounds like more than "a bit" low for a non-turbo. Highway I would expect at *least* 20MPG even with the slushbox, and 25 MPG would be more reasonable. Does the transmission feel like it's slipping at all? How's the fluid level? Definitely agree on the stage zero thing. Get everything working properly before even thinking about performance upgrades. Does it seem to run well?

Use GPS to check speedometer and odometer. Then post tire size. I'd guess that your cards tires are a bit undersized.

I would think 3k rpm for 65-70 mph is about right. like said above, tire size/ speedo error etc can make numbers look off

3k RPM is not unreasonable but 12MPG sure is.

Hm alright.

I bought the nicest spark plugs I could find, and installed them. I noticed that whoever installed the last ones didn't use any sort of grease, so they were very hard to remove. Except for the last two, which were so loose I was able to easily loosen them by hand.

Plug #4's wire was so loose it was basically hanging off. This might explain some things.

I also noticed that Plug #4 has what appears to be the end of a plug jammed into it, so it looks like I need to get new spark plug wires tomorrow. I ran the car with only 3 spark plug wires, and it ran terribly, so I shut it off.


Tomorrow I'll get the plug wires and give her a drive and see if it made much of a difference.

Quinnn said:

I understand this, as the button kicks the transmission out of the "overdrive" 4th gear. As I understand it, when the car is doing highway speeds, it should be in overdrive and the RPM shouldn't be as high as it is on my wagon.

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The button does nothing if you aren't in overdrive. Since it does something, your overdrive is working.

Khrrck said:

The button does nothing if you aren't in overdrive. Since it does something, your overdrive is working.

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This is precisely why I brought it up.

Alright well, new sparks and wires installed, no difference as far as I can tell.

The oil was changed right when I got the car, I did an ATF change, flushed the coolant, checked the air filter, ect.
The car needs to be aligned, but there is no way it could be causing the issue with my mileage.


Additionally, I'm not sure how slow these cars are supposed to be, but I know that mine goes 0-30mph in around 10 seconds, which seems really slow. I have to floor the gas pedal at green lights in order to keep up with traffic.

2800 = 70 mph on your car. You may have the kick down cable adjusted too tight. There should be one more "gear" on your car. A 1992 740 non-Turbo model should have an AW-70L transmission in it. The L stands for lock up converter. When the converter locks, you should see about a 200 rpm drop at highway speed.