Hi guys,

I just got back this weekend on a 500 mile round trip to see my ailing father and the 300sdl has been acting up. I'm not sure if it is the tranny, vacuum pump, or other and I was hoping for some advice. The drive was through rolling hills from southern Wisconsin to Northern Missouri. Anytime I floored it, or if the car was under load, it would shift down about 1,000 rpms and just needlessly rev before I would have to back off the accelerator to force it to shift down, then it would barely make it. Most medium hills I would loose 10-15 mph until I would crest them and then it would catch right up. In this period when it is downshifted and revving it fells like it is lurching slightly until after a few seconds I back off.

I've been wondering if I permanently damaged my tranny in the Rockies. In August I took it on a 2,000 mile round trip, laden with camping equipment and the family (no trailer--the car has never pulled anything). Once I got to the mountain grades I had to frequently punch down and it never had the effect as this past weekend until we returned. I noticed on the way back across I-80 on the rolling hills it would rev and first witnessed the slight surging motion.

Around town it's fine. I assume it's the transmission but I've never replaced the vacuum pump. Some of the shifts are rather sharp, and thought that it controls some of that but the loss of power on the top end doesn't seem like it.

A quick short history, The transmission was replaced at 125k before I bought it in 2000. I've taken it from 148k to 223k. The tranny was serviced about a year and a half ago (fluid change and filter) by the dealer. Over the nearly 8 years I've owned her, I've replaced basically all the typical things that go wrong with these cars at this mileage and then some except the vacuum pump. 3 years ago @ 200k, I had to replace (by dealer) the Injection Pump because a module that was part of the pump that controlled the fuel flow "under load" went bad. Overnight from a dead stop, it wouldn't accelerate moderately from a stop sign. When it got to cruising speed it was fine. The lack of power (that's relative, it's a 300sdl!) when punching down on it, albeit at a different point seems familiar.

Sorry for the long post, but wanted to furnish the history. It's been a great runner, but I've lost a lot of faith in the local dealer, since the my tech left a few years ago. There's been a lot of cost of determining problems (2 air condition compressors, 4 glow plug relays in just over 4 years) that I wanted to be directed in the right direction. The wife is starting to balk at the "investigating cost" and the thought of driving the Honda on long trips makes me bristle.

Thanks guys.

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Jeff Weyer
'87 300SDL 228k

Flaring does not indicate a problem with the vacuum pump. If it were the vacuum pump failing, it would be very hard shifting (probably accompanied by a host of other issues).

A MityVac is a great investment at around 50$.

I'd check to see if you're getting too much vacuum from the VCV to the tranny. Should range from 15 at idle to 0 at full throttle. Lots of threads detail how to check this. Might also be maladjusted bowden cable telling your transmission to shift way too low in the RPM range.

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Thanks UriahT. I've been meaning to purchase one of those things.

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Jeff Weyer
'87 300SDL 228k