by Goran Freske

There comes a time in every 1800's life when the overdrive exhibits mannerisms that even have the specialists baffled. I recently have had an episode that does not give me a great deal of confidence in the analytical powers of these "experts". To many of them, it seems, the understanding of the workings of the overdrive is something given to them by some divine insight, incomprehensible to us mere mortals. But the truth be known, the mechanical aspect of how the overdrive functions is really quite simple, as I was forced to learn because I didn't quite believe the mechanics' wild guesses.

Never having had any difficulty with the overdrive in the 22 years I've been driving 1800s on a daily basis, I scarcely glanced at the complicated cross sectional view of it in my manual, believing that if ever the time came to do any major servicing, I would probably have to consult a Volvo mechanic. Then the unthinkable happened. On my last annual trip to Washington State, in August, 1995, the overdrive started slipping. It was functioning normally when first engaged, but then the slipping was in direct proportion to the uphill grade.  All other functions of the drive line appeared normal, so I just didn't use the overdrive, slowed down so as not to overrev the engine, and proceeded to drive the 600 miles I had left to go.

Once settled down at my sister's place, I started looking more closely at that dreaded picture in my manual, trying to see if somehow I could get a working overdrive for my return trip to San Diego. I discovered to my amazement that the overdrive contains three clutches, two with linings and one "mechanical". I still did not completely understand the function of each based on the picture and the limited verbal descriptions in the manual, so I resigned myself to a slow journey home.

After I'd been home for a few days, and contemplating my manual repeatedly, I talked to Bob Skoog, a member of SDVSA and a person that had some experience with rebuilding overdrives, as he has with darn near everything on the 1800 cars. He kindly offered his help in taking the unit apart and ascertaining the problem, and, on the basis of that, I removed the overdrive from the car and brought it to his house. Everything looked perfect inside, including all seals and 0 rings, and, based on the slipping in overdrive, not GOING INTO overdrive, we concluded that the clutch linings should be replaced. I still didn't know for certain which of the liners came into play in overdrive, but, since we had the whole thing apart, it seemed like a good idea to replace both and start out fresh.

We started calling clutch and transmisson shops, asking if they could reline this particular overdrive clutch, but they had no idea what we were talking about! Then we caIled after market Volvo parts places, and they at least knew something about these clutches, but no one knew where they could be relined. Finally, we called Southland Clutch in National City, which for some reason we had overlooked, and they knew EXACTLY what we were talking about. In fact, they said, they had the material, and they could do the job right there! With great expectations I went down there the next day, and it did not make any difference to me that they could not do the relining in house but had to send it out, as long as I could get the job done, and done right.

About ten days later I got the parts back - I say parts because Bob wanted to get one relined, too, -and took them back to Bob's house. We spent a few hours assembling the overdrive, until we found out that one liner was too thick to even bolt the case back together. So we had to take everything apart again, so I could take the clutches back to Southland, so they could send them back to have a little material removed from the offending lining. By now I'm beginning to have a funny feeling about this whole business. Another ten days went by, and when I picked up the parts, I noticed that they machined off some material on the other liner as well. I commented on that fact to the counterman, but believing in their expertise, as he did, I accepted the parts. By this time I had the overdrive at my house, so I went home, put the unit together with the new clutch, and put it back in the car.

As I was backing the car out of the garage, the whole car started shuddering, as when you have a grabbing engine-to-gearbox.. clutch. My driveway slopes a little bit up towards the road, and as I was backing up to get out to the road, I lost reverse completely. I rolled back to the garage, turned the car around by pushing, and proceeded in first gear out to the road. No problem. The road slopes down pretty severely from my driveway, and, letting up on the gas, I noticed that the engine did not provide any braking power at all. Since I had the car on the road, I decided to test it in overdrive. The first time I flipped the o-drive switch, I had the engine clutch depressed, and slowly let it out, prepared for anything, from a complete lockup to worse slipping than previously. It appeared to be working fine. I flipped it in and out of overdrive several times, even on upgrades, and at least my original problem seemed to be solved. But now I had other new ones; no reverse and no engine braking.

After having talked on the 'phone and driven to numerous shops, being careful where I parked, trying to get a consensus of opinions of the problem, I concluded that I would have to figure this one out myself, since I did not believe anyone's diagnosis. Again I returned to my manual, and an old overdrive that I have lying around, and finally a picture of how the overdrive really works slowly formed in my feeble mind. I was convinced that the problem was with the replaced clutch lining, so the only way I could prove my suspicions was to again remove the overdrive from the car, disassemble it, and look at the liner. Well, I was right. The liner showed evidence of only making contact over between a third and a half of the total engagement area.

For anyone who is still with me in this tale, I will attempt to put my understanding of the workings of the overdrive into words in the following paragraphs. I will be concentrating on the mechanical aspects, assuming that the hydraulic system is functioning properly.

Quoting my manual; "In direct drive, power is transmitted from the gear box mainshaft, through the unidirectional clutch, to the output shaft".

I'd like to leave the reader to ponder this thought until next month's issue of 1800 NEWS, since I don't want to hog the whole newsletter with this story.