Transmission problem on Suburban 2500LT Automatic (2WD)

Discussion in 'Chevy Suburban Forum (GMC Yukon XL)' started by baznicholson, Feb 3, 2011.

  1. baznicholson

    baznicholson Member

    Apologies for not being online for a while - things have been a little rough here...

    As I have now been out of work for 4 months, I decided that the Suburban had to go unfortunately. However, yesterday while driving home from a potential buyer, my transmission let go. I have absolutely no knowledge of these systems so would appreciate any advice.

    While accelerating, there was a clunk from below and it appeared to jump out of gear. A gear then reselected but at 80km/hr (about 50mph), it's now revving at close to 6,000rpm. 1st and reverse seem unaffected and there are no dash warning lights on. Transmission fluid levels are all good and the fluid seems fine - no discolourisation or burnt smell.

    Last week, the rear UJ failed and allowed the propshaft to drop onto the road at 75mph - could something have been knocked out of whack by this? The car has been driving fine, with no nasty noises since then.
  2. stephan

    stephan Rockstar 4 Years 5000 Posts

    Hey Baz, welcome back. Sorry to hear about your trouble. This is just a shot in the dark, but when your rear U joint broke, if the drive shaft was whipping around before it fell out & caused a LOT of vibration, it's possible the vibration caused your trans filter to work loose & it could be sucking air & causing a low pressure situation. I don't recognize what year your Sub is. What trans does it have?

    It also could have ruined the rear trans seal & dropped a lot of fluid & low fluid level will cause low pressure if it's alternately sucking air, but you said the fluid level was ok. How are you checking the trans fluid level.
  3. baznicholson

    baznicholson Member

    Good evening Stephan, thanks for the quick response...

    The Suburban is a 2001 model with automatic transmission. That is about as much as I know as regards the box - is there a plate anywhere giving more info?

    I checked the auto transmission dipstick in the engine bay, with the motor running, and all appears within limits. I have checked every day for any leaks or loose parts underneath since the UJ failure last week - again, all seems to be in order. Where would I look for the filter?

    Cheers, and sorry I can't be of more help re your questions
  4. stephan

    stephan Rockstar 4 Years 5000 Posts

    ok, if your fluid level is up then the only other thing I can think of is the filter could have vibrated out & is sucking some air which would drop the pressure & screw up the shifting. When the u joint broke, did it cause a lot of vibration & shake the crap outta the Burb, or did the drive shaft fall out immediately?

    The filter is inside the trans pan. To check it you would have to drop the pan & drain the fluid out of it.
  5. baznicholson

    baznicholson Member

    I'd just pulled out to pass a semi so was pushing about 75mph when the UJ let go.... it's probably safe to say that there was a fair bit of vibration...!! The drive shaft actually stayed attached and didn't contact the road (luckily)

    I have been driving the car every day since the incident and this is the first time I've had a problem but, with the roads around here, it may have taken a few days to really work something loose. I'll check on the filters tomorrow.

    Thanks again, and I'll let you know what we find tomorrow...
  6. stephan

    stephan Rockstar 4 Years 5000 Posts

    If the filter is secure, & not dirty or plugged, then look for anything else that could be loose or broken. Make sure the valve body is tight & none of the bolts are coming loose. Also, carefully pour the fluid out of the pan so you leave the sediment in it, so you can look it over. A certain amount is normal but big pieces aren't.

    **Just for drill before you pull the pan, take a look at the shift cable & see if it all looks normal, or if the drive shaft could have whacked it & stretched it, kinked it, etc. Not too likely but I don't know how much room the drive shaft had for flying around under there, or if the shaft also came out of the tail shaft before it was all over with..
  7. baznicholson

    baznicholson Member

    Great, thanks for the pointers. I'll get onto it tomorrow. In tare a couple of quick pics from the day it meantime, here's a couple of quick pics from the day the UJ disintegrated...

    IMG_4159.jpg IMG_4160.jpg
  8. baznicholson

    baznicholson Member

    OK, update.

    I (and some helpers) dropped the pan and checked the filters, cleaned and reset all of the electronic connections but so far, have had no joy in resolving the problem.


    The symptoms remain as following (and explained a little more clearly this time):

    Reverse, 1st and 2nd gears work, although 2nd appears to be slipping. Top gear is gone entirely meaning 50km/hr equates to 3200rpm. When I remove my foot from the gas pedal, regardless of speed, the box immediately shifts to neutral.

    Someone has suggested that the governor may have failed - does this sound plausible? Also, is it possible to download schematics or guides for the 700R4(?) gearbox?

  9. 1991 Suburban

    1991 Suburban Rockstar 100 Posts

    If it is a 2001, 1500, then you have the 4L60E, not a 700R4. As for any schematics, the only advice I can give you is to google search. You'll eventually find what you are looking for. Good luck with the fix...

    Just noticed that you said it was a 2500. Depending on the engine (8.1 or 6.0) you could have either the 4L60E or the 4L80E (the 80 came on 7.4 or 8.1). Sorry for the mistake.
    Last edited: Feb 7, 2011
  10. baznicholson

    baznicholson Member

    Thanks for the info Jess - much appreciated. I'm going through the Google search results as we speak...!!

    ---------- Post added at 06:24 PM ---------- Previous post was at 05:09 PM ----------

    Found a manual for the 4L60E and downloaded it as a .pdf I'll start going through it tonight and see what transpires

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