300SD, shift problem, HELP!!
 

Last week 3/4 of the way thru a 10 hour trip my beloved prize became haunted by demons. Stopped for fuel and found while getting back on the road that the xmission decided to not shift {and very harsh when it does} till about 3200 rpm 1-2-3 and wont go into 4th at all unless I go to neutral and then back to drive, then it goes into 3rd for a second and then 4th. This is a xmission that has never had any issues and had a fluid and filter change about 20,000 miles ago. I have searched the posts for 2 days and checked everything I could find. Fluid level right on the top mark hot. Unhooked the kickdown at the pedal and also the xmission, checked the vac- 12 in at the feed to the modulator which drops to near 0 as throttle is opened, modulator holds 12 inches on the mighty-vac for as long as i cared to watch it. No other vac leaks found {envy me??} I think that I saw in my search that a blocked filter causes some kind of pressure rise but I can't find it again. Does anyone think a fluid and filter change might help or would I just be barking up the wrong tree?

You have certainly covered your bases well.

I was hoping for another kickdown switch. :D

The fluid and filter would almost certainly accomplish nothing if it was done 20K ago.

Take a look at the Bowden cable. It might be possible that this cable is hanging up. If the cable was pulled to a typical position when heavy pedal is used, the shift would be delayed until over 3000 rpm. This is normal.

Now, if the cable fails to return to its stop, due to internal friction, the transmission thinks that you have stomped on the pedal again and delays the shifts.

If the cable fails to solve the problem, it is likely a problem internal to the transmission. However, this is the least likely scenario.

Thanks for the reply Brian, I should have mentioned in my first post that the bowden cable adjustment makes no difference to the shift point, all the way out or in on the adjustment and it acts just the same. Have you or anyone else ever changed one of these cables? Mine seems to pull to a stop when I try it by hand unhooked from the throttle so I feel that it is still hooked up in the tranny but maybe a return spring or something has gone south. I feel this just has to be some sort of mechanical issue instead of pressure or vac.

Can you check the connection point at the transmission to determine if the cable is moving properly all the way down? Seems like a longshot, but might be worth a look. I'm not positive, but, I would guess that the trans must have a return spring to pull the cable back to the idle stop???

I have not changed one of them. However, if you disconnect the cable at the transmission and the problem remains, you have effectively ruled it out.

I agree that it is not vacuum related. Now, governor pressure is a different story.

shifting
 

how about a faulty kickdown or a faulty electrical connection to same?

........

thanks guys for bearing with an idiot old fart like myself, I was just assuming the miles since last trans service...when I actually got out the records it turned out to be more like 40,000+ , boy does time and mileage fly by! Long story short, had to pull the pan to check bowdin cable hookup so did fluid and filter at same time, now she shifts like a dream,not even noticible from gear to gear. You got to love these old diesel cars, they even forgive a person for gross neglect {fourty lashes to me with a vacume hose} and come back strong :D
this has to be the best site on the internet, very helpful in keeping our fine autos on the road and in good shape.
somewhere in my search thru the xmission posts for info I found one that said "change fluid and filter first" best advice I have ever heard and if I had taken it I would have saved a few hours of chasing myself around in circles.

Glad to hear it wasn't a transmission failure. I was getting worried for you! Well, great news. Great news!!! :)

That is good news.

Any sign that the filter was clogged?

Even at 40K, the trans should not have accumulated enough debris to prevent shifting. Some people never change the fluid and the transmission typically tolerates it.

That was the very strange part of the whole issue, for the car to seem fine, make a fuel stop and everything be all to heck getting back on the interstate. I was sure it must have been a failure of some sort which is why I did all the trouble shooting to find everything { vac+ bowdin+ kickdown switch} AOK. Fluid looked fine on the stick, no smell and seemed a good red color but once i got it dumped in a bucket i could see that it was quite a bit darker than normal. Filter looked kind of plugged up but no more than they usually do. {that is just an opinion}. I was actually just dropping the pan to have a go at the bowdin hookup in the xmission when I got a look at the color of the fluid in the bucket and THEN got out the file on that car to find I was overdue on a service that i thought i had done but didn"t. Why this resulted in hard, high RPM shifts instead of slippage i have no idea. Drove her to work today, 35 miles up and down the mountain and she shifted beautifully.
beats me what all this was really about but the new filter and fluid did the trick. Wish now I had changed over to synthetic fluid but I figured dexron was good enough for a wild try at a fix. You guys are great and thanks for the help and concern for "The Big Dog". You can bet that wifes "Yellow Dog" will be getting its xmission service on time!

Good news indeed as I already stated. However I share Brian's concerns. 40,000 miles isn't quite enough to cause such a problem... at least typically. I wish you had collected a sample of that old transmission fluid to send off for an analysis. I hope your transmission isn't wearing out abnormally fast.

Stephen, aka "Smooooth", has "The Big Dog" as well. :D

His dog is a bit bigger however. ;)

Braverichard, where could i send a sample for spectro analysis? Haven't done that since my Air Force days, many moons ago.
I did pull a clean sample off the top into a glass jar and shoot a photo-flood thru it, no debri that i could see with a mag.glass and a swish or three with a very strong magnet resulted in no metal sludge. I usually do the magnet trick with my used oil every change. To be truthful, if i came up against a high dollar repair i would probably just park it next to the rest of my parts storage vehicles and start looking for another under 150,000 mile SD.
Brian, I meant to ask you last time, how do you like the SDL? I really want one but I hesitate to leave the 5 cyl that I know and love. { and also have a parts car for, maybe two if my SD is going down}

I have a love/hate relationship with the SDL.

I love to drive it. It has an engine that is a technological marvel and it's almost as quiet as a gasser at 75-80 mph. It gives you the feeling that it weighs about 1000 lb. more than the SD, even though it is only 200 lb. heavier. It's ridiculous to own one for driving around town and I only take it out on the highway.

The hate part is the maintenance. Most of them need the typical things that an 18 year old vehicle needs and the parts are expensive. I've owned this one a bit over one year and have put over $3.5K in parts. This includes new tires and a new Alpine head unit. But it also includes a bunch of suspension components and electrical switches and relays and a driver's seat spring. I still need to get the cruise and the climate control repaired and this will run another few hundred.

I look at it as a long term project. I anticipate getting down to less than $1000. per year commencing in year three. Of course, this is provided that the head does not crack and the head gasket remains intact, no sure thing with this primadonna engine.

If you decide to get one, find one with an excellent body and very good paint. If you have to put $5K in one, you sure don't want to do any body and paint work to add to the mechanicals. After residing underneath this one all day Saturday, I do feel good about the fact that it lived in Florida for all of its life and the PO had an 8.5 repaint on it prior to my purchase.

thanks Brian, looks like I will stick with the SD 5 cyl line. Love the looks of the SDL but don't really need the extra room to pile stuff in, just such a beautiful car it's hard to resist. :)