Been working on an '83 300TD with 210K on the clock for a while now. The transmission was replaced about 30,000 miles ago and has always shifted really damn firm. Well yesterday when leaving a parking lot I shifted in to drive and started to take off. Got a few feet then suddenly the engine revved up and the car went nowhere. Shifted in to reverse and backed back in to the parking spot, put it in park, shifted back in to drive and it was fine. Still shifted real hard when I left the parking lot like it usually does. A few stop lights later when taking off, shifting in to second gear was totally unnoticeable. That seriously threw me off. Shifting in to third it slipped a bit before settling all the way in to third. Fourth gear change was unnoticeable as well. Shift timing seemed about normal. A few miles down the road there was another stop light and when taking off the transmission was back to it's normal harsh shifts. I pulled over and checked the fluid, it was fine. Clean, full, and unburned. Went to take off and it slipped so badly the car would barely move! A few moments later it started driving like nothing had happened. The flaring and super soft shifts kind of came and went until I got the car home, pretty much hit or miss.

So today I pulled the car in to the driveway to check for any vacuum leaks, although I'm inclined to believe with no vacuum it'll shift hard and too much will make it super soft and flare. Didn't see anything wrong. Went to pull back to where I have it parked normally and reverse would not engage. Instead I heard a whirring sound from the transmission when I tried to engage reverse or drive. I tried to get it to go in to gear for probably a minute straight. I shut the car off, put it in park, restarted the car, and viola it went in to both reverse and drive quickly. Once it was parked I tried engaging reverse again and it took a few seconds but it went in, same with drive. I checked the fluid and it was low so I added a little more than a half a quart and took it around the block. The flares were gone but it shifted a little smoother, actually it felt pretty nice... about a happy medium between slush box and neck-jarring.

I unplugged the two vacuum lines from the modulator on the top of the IP and plugged them. Drove it around the block again and the shifts weren't any different. That could be bad. But I don't really see why such a new transmission would suddenly start acting up, especially if the shifts were always harsh enough that there is no way any slipping was going on.

I'm in the process of trying to sell this car and either this is a sign that this thing needs to get the hell out of my life or it's become so attached to me that it doesn't want to go!

If I have to bite the bullet and put a tranny in this thing... well that just sucks.

it wouldnt necessarily be "bad" or indicate vacuum wasnt an issue if you plugged the lines from the IP and nothing changed, because the modulator on the transmission itself could also be going bad intermittently.

Been digging around a bit and read that unplugging the modulator on the IP *should* make the transmission shift as hard as possible, if this is true then mine isn't cooperating. You're thinking the modulator on the IP is fine but the one on the transmission is failing so that's why there wasn't a difference when unplugging the lines?

i'm thinking it might be possible. you can put a mityvac on the line going to the trans to see how it acts, without having to get under the car. if its leaky it could still mean the line has a leak somewhere between the IP and the trans modulator, in which case you'd need to get under the car and test the modulator directly.

Right on. So a vacuum issue of some sort will cause it not to engage reverse or drive?

to be honest, im not sure. but if its only got 30k miles on it.. its about 200k away from internal failure i would think? its probably worth seeing if its a vac problem...

As far as I know, a vacuum problem will not cause non-engagement. It's something else. Next time it doesn't engage, pull one of the cooler lines and see if you have fluid flow or not.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

Will do. If a pump went tits up that would explain everything. Where are they located inside this transmissions?

No.

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When cryptography is outlawed, bayl bhgynjf jvyy unir cevinpl.

One pump is at the front but it has a rear pump also I think. I believe a failed front pump can sometimes be overcome by a functioning rear pump. Is that right?

__________________
1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

Drained the fluid and put a new filter in. The inside was squeaky clean as was the filter, pan, and fluid. After that it didn't want to move but after a while of shifting the selector between reverse and drive it started engaging, then driving. Today I started the car after sitting for two days and the transmission worked great.

There's a whirring noise when in park or neutral that goes away in reverse or drive. In drive it's quiet, shift in to reverse and there's the whirring noise that goes away as it engages reverse. Then reverse is quiet, shift in to drive and there's the whirring noise that goes away as it engages drive. Put it in park and the whirring starts back up again. Sounds like a whirring mechanical actuator.

Been looking in to the B2 piston thing, seems likely but at the same time not really.

Hi Kingman, did you ever sort this out? I'm having a similar problem now with my '79 300TD...

Hey there. I didn't exactly get it "sorted out" per se but the fluid and filter change seemed to have cured the problem, along with moving a transmission vacuum line so it actually sees proper vacuum - it no longer slams through the gears and engages drive/reverse quickly and consistently.