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OD problem in 740?[ALL/1998] posted by Michael McBroom on
Wednesday, 30 April 1997, at 12:47 p.m.
Hi Folks,
I just bought this car, so I'm not really sure if there's a problem that can't be cured by a bit of adjustment, or if it may be something I'm doing wrong. The car is an '87 740 Turbo Wagon with a 4-speed OD transmission.
While driving it home from the dealer, I noticed that it would not go into OD. I suspected that OD may be load-sensitive, so I slowed down a bit, switched off the AC and tried again. This time it went into OD. When I switched the AC back on, it went back out of OD.
Last night, I read through the manual and found out that I'm supposed to depress the clutch to shift into OD. I hadn't been doing that, so I'm gonna give it another try in a little while. Today, I called the place where I bought it from (they specialize in Volvos) and talked to a mechanic. He told me that OD is *not* load sensitive, and that one did *not* need to depress the clutch to engage the OD, and that there is a sensor switch which tells the OD when the transmission is in 4th gear. He said that if the switch is mis-adjusted that this can cause it not to go into OD, or to spontaneously go out of OD. He said that if it goes into OD while pressing the OD button and rocking the shift level back and forth once it's in 4th, this is a good indicator that the adjustment of the switch is the problem.
I'm about to go give it another test drive, but I thought I'd post this anyway to bounce it off of those of you here. It still seems to me that it was the additional load of the AC that was causing OD not to engage.
Best,
Michael
Re: OD problem in 740?[ALL/1998] posted by Michael Smith on
Wednesday, 30 April 1997, at 9:56 p.m.
Mike, I would use the clutch when engaging or disengaging the overdrive. If you look at your tech manual and find an exploded view of the OD unit, you'll see the conical clutch pieces that are forced (via hydraulic pressure) together when you actuate the switch. You do not want to wear these out !!! A rebuilt OD unit from Volvo can cost from $1300-1500. I had a similar problem with my OD unit on my 86 740. After making the usual "electric" checks, I decided to check my fluid level. The level was correct, but the fluid was wrong!!! On a trip to Dallas, Texas, I decided to have my overdrive serviced by Volvo of Richardson, a franchised dealer with a very high service rating. Well, these idiots drained the the unit, changed the filters that I provided them with and, then, proceeded to refill the unit with DEXRON instead of ATF Type F. Well, it just never worked right. It would slip in and out of overdrive at random. The only time it worked properly was at night and during the winter, when the ambient temperature was below 45-50F. I finally fixed the problem by draining the DEXRON, re-changing the filters (about $32.00), and refilling the unit with Red Line Oil's Racing ATF Type F. Works great. M.P. Smith, Blacksburg, Virginia.
Re: OD problem in 740?[ALL/1998] posted by Michael McBroom on
Friday, 2 May 1997, at 12:08 a.m.
Now that I've been driving the subject 740 for a few days, I have a better handle on what it is and isn't doing. Specifically: The OD does not always engage, but once it's engaged, it stays that way. And, contrary to what I'd written in my previous post, the A/C does NOT seem to have an effect on its operation.
What I notice now is that, most typically after hard accelleration, such as accessing the freeway, the OD will not engage. If I slow down, it still won't engage. Typically, however, after a few miles of city driving have elapsed, I can get it to engage again. On the freeway, however, it doesn't seem to want to go into OD, no matter what. There have been a few times where I've been cruising sedately on surface streets, and wasn't able to get it to engage, but this is not nearly as common as the above situation.
The OD itself seems to be operating smoothly. No untoward noises, clunks, clangs, or howls. So, I'm hoping the problem is minor, and doesn't lie with the OD's mechanicals. I have not checked the fluid level yet. I suspect I should go ahead and have the fluid and filters replaced, since I have no idea how long it's been since its last service.
Re: OD problem in 740?[ALL/1998] posted by Rob MacTurk on
Thursday, 1 May 1997, at 1:33 p.m.
You said that the OD kicked out when the A/C was turned on. Is this consistent? If so, I'd suspect the electrics. To the best of my knowldge, the A/C and OD are independent of each other in terms of operation. You may want to check that wires to the shifter OD switch are OK. They run up next to the reverse pullup and the insulation can wear through after a while making for erratic operation.
Rob