Hi All,

I have been having a really strange thing happen with my 94 xlt 4wd Here are the symptoms.

A while back I was getting backfires on start up that would blow of the vacuum line to my trans so I took a tyrap and affixed the vacuum line to the diaphragm on the trans.

I rectified this by changing the plugs and I make sure that when I start the truck I really get it started (don’t disengage the starter to early as this can result in backfire if the motor is not quite starting and a backfire can result) Also indicates you may need a tune up as these motors will run with plugs that are almost non existent.

I had a backfire the other day due to rushing and it blue off all the vacuum hoses on the "spider" at the intake.

I now have been having the following problem. I am going through 2 quarts of ATF every 200 miles or so. But I am not leaking it. I have also notices that when I am sitting at a light and take a left turn the motor will ping badly and it blows allot of blue smoke out the tail pipe (like some one is poring atf in the intake). It will also ping a bit when I am crusing and take left turns but no noticeable smoke.

One last thing I was looking at the "spider" on the intake and found Trans fluid in the vacuum lines.

Here is my "crazy" diagnoses

The backfire with vacuum line ziptied in place to the diaphragm on the Trans caused the diaphragm to brake or at least leak. Now Trans fluid is being sucked up in to the intake. Being that the diaphragm is on the right side of the Trans, left turns cause the Trans fluid to slosh to that side causing a tremendous amount of trans fluid to be sucked into the motor and then be burnt causing smoke and pinging of the motor.

One last thing. The Trans operates fins all gears are good shifts properly od works fine. Before this started the atf has always been fine (not burnt etc)

What i propose as the fix is to do a filter change as it has been 40 k since last one and while I am there I am going to replace the diaphragm that the vacuum line attaches to (assuming that this can be done with Trans in the truck)

What do you all think???


Respectfully


Dean
94 xlt 4wd 125K

 

You may be crazy, but I think you've got your missing atf problem figured out Replacing the diaphragm is fairly simple. It's behind the heat shield on the rt side of the tranny. you'll have to locate and remove a nut that holds the heat shield bracket to the tranny. I think it's a 10mm. The diaphragm is held in by a bracket that fits around a collar on the "stem" that fits into the tranny. You don't have to loose a large percentage of your atf to cause serious damage so I'd change that vacuum valve right away. On the backfire blowing the lines off of the "tree" .....have you checked codes? Let me know what solves that problem......best of luck

 

good point re codes I will chk that

Dean

 

Well I just wanted to let you all know that it was the diaphragm on the Trans that was the problem. I replaced it and now there is no more pining etc. I also am not using any Trans fluid and no more smoking on left turns.

BTW replacing it was a real pain you have to take the cat out. Thanks to my friend who is also the local mechanic I could use a lift and torches and stuff but it was still a two hour job. Or should I say it was 1 hour and 50 minutes of getting to it and reassembling the exhaust and heat shield and ten minutes to changing the diaphragm and the piece of vacuum line.


Thanks to all that replied


Dean