Hi I have a 99 chevy Astro van with a 4.3li vortec (w code)and a 4L60E transmission all with about 219,000 miles.In the morning when I leave for work the tranny slips through the gears, sometimes bad , sometimes not so bad. If I drive for about 15 minutes and then stop and shut off the engine and wait for about 20-30 minutes, the slipping is gone and the van runs normal again, also on rainy days or nights that it has rained the slipping is even worse. At a stop if I start out slow and drive at normal street driving speeds (20-30 mph) the slipping is the greatest, but if I push down on the gas and race fast off the line it doesn't seem to do it .Last year I did a tranny service, changing the ATF fluid and a filter kit. Its been doing this for a while and I know I need to do something soon, I've asked some people and they all tell me that the tranny is going, I hope not I really can't afford that, if anybody can tell me whats going on I would sure appriciate it. Thanks

Hi I have a 99 chevy Astro van with a 4.3li vortec (w code)and a 4L60E transmission all with about 219,000 miles.In the morning when I leave for work the tranny slips through the gears, sometimes bad , sometimes not so bad. If I drive for about 15 minutes and then stop and shut off the engine and wait for about 20-30 minutes, the slipping is gone and the van runs normal again, also on rainy days or nights that it has rained the slipping is even worse. At a stop if I start out slow and drive at normal street driving speeds (20-30 mph) the slipping is the greatest, but if I push down on the gas and race fast off the line it doesn't seem to do it .Last year I did a tranny service, changing the ATF fluid and a filter kit. Its been doing this for a while and I know I need to do something soon, I've asked some people and they all tell me that the tranny is going, I hope not I really can't afford that, if anybody can tell me whats going on I would sure appriciate it. Thanks

It may be that your tranny is in it's final days. I can tell you something that I did which may buy you some time. Simply change your tranny filter and 3 quarts Mobil 1 transmission fluid and 3-4 pints of Lucas transmission treatment. Changing the filter is not all that hard--you have to methodically remove the 14 or so bolts on the pan--you will lose about 5 quarts of fluid while doing this so be sure to have a large catch pan. Then simply jiggle the old filter out as the front snaps up into a seat--sometimes the metal seat will come off and you can easily fish it out with needle nose pliers. Then snap your new filter in. Be sure to clean out the pan as it will have a bunch of crud and metal filings around the magnet located in the pan. I see in your post you did a filter fluid change but using the synthetic ATF combined with a large dose of the lucas may give you enough time to devise a battle plan. I have owned 5 Astro-Safari Vans and if I do this every 100k, the transmission will usually out live the van. However since your van has begun slipping I feel this can only buy you some time. I have never heard of anyone taking a vehicle to a transmission repair shop and received good news. I would use any time this may give you to shop for a used or rebuilt tranny out of a simular model van--there should be plenty around. These trannys aren't known for premature failures. Anyway--good luck and let us know how it turns out!

Maybe I can add something for you to consider. Remember, transmissions are hydraulic devices and the transmission fluid besides lubricating also is the hydraulic fluid in this application. The valve body inside the transmission oil pan is what provides the passage ways for the fluid to do whatever is needed at any moment. This is the flat looking machined part inside the transmission oil pan with all the bolts holding it up inside the transmission. These bolts can and often become loose and cause pressure losses for various functions. A shop manual can tell what areas control different functions. The area for reverse is one function. I have had that area get loose and cause reverse to be real sluggish. I tightened it and it worked great again. (Of course I tightened all of the bolts to the proper torque.) This in my opinion should always be checked when the pan is dropped to change the filter and oil. Hope this helps.

Maybe I can add something for you to consider. Remember, transmissions are hydraulic devices and the transmission fluid besides lubricating also is the hydraulic fluid in this application. The valve body inside the transmission oil pan is what provides the passage ways for the fluid to do whatever is needed at any moment. This is the flat looking machined part inside the transmission oil pan with all the bolts holding it up inside the transmission. These bolts can and often become loose and cause pressure losses for various functions. A shop manual can tell what areas control different functions. The area for reverse is one function. I have had that area get loose and cause reverse to be real sluggish. I tightened it and it worked great again. (Of course I tightened all of the bolts to the proper torque.) This in my opinion should always be checked when the pan is dropped to change the filter and oil. Hope this helps.

Great Post---Could you follow up with the proper torque numbers.

The only torque reading I can find, for a 350 transmission is 130 inch pounds. I expect this should be the same for yours. If I remember correctly, the bolts are 1/4-20. 1/4" diameter and 20 threads per inch and these are real common. This same transmission I did this about ten years ago on, a 1975 Chevrolet that I bought new, is doing it again, so this time I am going to measure the deph of the holes and use lockwashers on thiese valve body bolts, even if I have to, and/or can use longer bolts. When I saw your post, I knew right away that you might have the sme problem. It happens a lot, the transmissions mechanics know about it and it is up to the rest of us to find out for ourselves. The factory doesn't use lockwashers (why not) and no one I have seen adds them later, but I will.

Now with torque reading on all bolts, especially small ones like these, the torque reading helps newbies get in the ball park on how tight they need to be without braking them. Most mechanics with experience just do this by feel. Unless its with critical torques like head bolts for instance, but a lot of torque specifications are not that critical. After you have wrenched on a few hundred bolts you can develop a feel for how snug they need to be. Adding lockwashers if you want to try that idea, adds another "feel" to the process, you can "feel" what the lockwasher is doing. I am going to add lockwashers to mine but remember I am going to make sure to check the bolt holes for depth to make sure it will work. On something like a valve body mounting the depths might vary too, so I will check for that. These kind of things take time that most mechanics are not going to take the time to do, unless its their own car or your are their buddy, but I drive the car and I don't want ever to be sitting by the side of a road, so I, like others on here will take the time to do it right. I will also change the filter and change to synthetic oil. (I have switched to synthetics all around, I have a Chev with 130K miles and a Ford with 165K miles that run like new and don't burn oil. synthetics can go longer without sludging up, the oil filter doesn't weigh that much more than when you put it in from sludge, and oil pans stay cleaner, plus the cost works out to be about the same. The engine lasts longer too, so now we put synthetics in transmissions too. Sythetics can take the heat and they don't need additives which helps even out the cost differential that people think is there. (I really don't work for Mobil.)

If you do this, lets us know how it goes.

Thanks for the help in this thread Bowtie, it should help medina, and this transmission having metric bolts is something I didn't know about. The transmission in the Astro I am working on was rebuilt by someone else, not me. I think I remember all the bolts on the last valve body I last had anything to do with were all the same length. That was a long while ago. By the way have they started putting lock washer on them yet? I am almost done with my brothers 2001 Astro and then I will drop the pan on my turbo 350 and do as the suggestion I submitted.