4L60 1st gear no torque - sometimes....

[zGerman]

I searched the forums for 1st and First and had over a thousand hits so I thought I may ask the xperts.

My 2001 Astro has about 160K miles, a stock 4L60 automatic paired with a NP231 TC. The problem is that at times the first gear lacks torque if in high range. For example I tried to drive up a trailer ramp last week and the engine went to 3500 rpm but the vehicle only rolled up to the ramp and stopped. Than it felt like it "clicked" and it drove up normally. I had this before a few times for example in sand except the click, never noticed that before. TC was in 4H and it was trying, engine revving but not going. Obviously I am not doing this for more than a few seconds to avoid damage. I can make it easier for the transmission and go in to 4L and all is well. Also street driving doesn't seem to be impacted but I also drive pretty gentle.

Fluid level is OK. Fluid color is OK. Solenoid? Any suggestions on a test procedure?

[Mmusicman]

TC was in 4H and it was trying, engine revving but not going...

Need to determine if this issue only happens when you are in 4H.. or any range.
In other words.. need to determine if the problem is in the TC or the trans.

I can make it easier for the transmission and go in to 4L and all is well. Also street driving doesn't seem to be impacted...

Based on what you describe.. sounds to me like an issue with the TC... (not the trans)
The TC is NOT part of the trans.. it is simply mounted to the back of it.

Sidenote: If you are utilizing the "extra 4L switch" to the computer.. you need to be sure it is not engaging in 4H

[zGerman]

It happens in 2H and 4H. My TC is a manual operated case with a mechanical lever. Using 4L puts a 2.7 or so gear reduction between the driveshaft and 4L60 making it much easier to move the van. I think the TC can be ruled out safely as the cause.

I dont seem to have any other gears slip except 1st and only if above normal tourque is needed using High range in the TC.

If the 1-2 solenoid is faulty does 4L60 may try to start from a full stop in 2nd gear?

[MechBob]

What position is the transmission shifter in,when it acts up?

[zGerman]

D in 4H - Vehicle was stopped in 4 inch of sand, unable to take off and did not spin tires but some torque was evident
D in 2H - Vehicle was attempting to go up a trailer ramp on pavement, some torque was evident but no go

Either way, the engine was applying torque to the drive train just not a lot even so the engine did rev up. Meaning the vehicle approached the ramps normally but wasn't able to climb them until it suddenly "engaged" and drove up like one would expect. During the sand experience I just shifted to 4L and all was good for the moment. But something is foul.

I am a gear head but most all my vehicles had been stick shift. My experience with diagnosing and working on automatics is close to zero.

[dcsleeper]

if it were me...
I would put in a can of seafoam trans tune. drive it for 10 miles or so. this is for cleaning
Then drop the pan and change the filter.

yours is one of my favorite Astros

[MechBob]

OK.Next time it acts up,pay attention if the PRNDL lights change or flicker.Also,start shifting the trans down one notch at a time,I bet van moves when you hit 1st.Sounds like trans is sometimes dropping into default mode,which causes 3rd gear starts.However,2nd gear starts happen sometimes,also.Many things can cause these,so try and narrow it down,first.

[Mmusicman]

..Meaning the vehicle approached the ramps normally but wasn't able to climb them until it suddenly "engaged" and drove up like one would expect.

Well yes.. what you further describe here certainly now sounds like a transmission issue (slips then engages). I've had worn older transmissions do this...typically due to a lack of internal hydraulic pressure. Once proper pressure is achieved.. the clutches are engaged. My "guess" is that this is likely either a worn hydraulic pump, or a sticking hydraulic valve. A clogged or restrictive filter can also be a major contributor, slowing the ability to pump up the pressure. This low pressure and sudden engaging can certainly cause further damage too.

How many miles on your trans?
It may be on it's way out?
(but maybe you can squeeze a little more life out if it)

if it were me...
I would put in a can of seafoam trans tune. drive it for 10 miles or so. this is for cleaning
Then drop the pan and change the filter...

Exactly. I've had good success un-sticking valves (with 2 different high-mileage transmissions) using SeaFoam's "Trans-Tune". My 92 occasionally wouldn't shift into 2nd, TransTune cured it immediately, and has been working fine since. In my 2000, valve stuck completely leaving me no forward motion at all (similar to your situation). In both cases, after pouring it in, it worked almost immediately, and completely fixed my sticking valve issues.



But it is designed (like radiator flush) to be used temporarily.. then the filter and fluid should be changed. It's a good process to just run this though before you do a filter change anyway. This quality major-name product is available at Walmart and most auto-parts stores. If it's a weak or worn pump.. then the TransTune probably won't help and you're likely looking at an eventual rebuild. But the fact you say it "suddenly engaged" leads me to believe it's more possibly a sticking valve, or a clogged filter, or both. This is worth a try... considering the alternative. But besides the TransTune you'll need a filter (w/gasket), and replacement fluid too.

Sidenote: The 700R4 in my 92 has close to 300K miles on it, with original pump. Despite fixing a sticking valve (preventing proper 2nd gear shifting)... one of the other "cures" I did to help with my worn old pump was to replace the stock servo with a Corvette servo. Not only did this help to improve sluggish performance, but it improved a similar condition your describe (delayed gear engagement), as well as dramatically firm up and improve shifts, and improve converter lock-up as well. It seems to have improved hydraulic pressures overall, and was a good "band-aid" on an old worn trans.

1) Corvette servo in my 2000:
https://www.astrosafari.com/viewtopic.p ... o#p1478806

2) Corvette servo in my 92:
https://www.astrosafari.com/viewtopic.p ... o#p1185682

3) Benefits and results of Corvette servo in my 92:
https://www.astrosafari.com/viewtopic.p ... o#p1187362



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During the sand experience I just shifted to 4L and all was good for the moment. But something is foul.

Well that's one of the nice big benefits of 4L, as well as taking the strain off your transmission.

Side story: I ultimately damaged my transmission on a jobsite once (years back when my van was still AWD), trying to pull a 5000lb trailer in sand. At full throttle, the engine revved (normally to the stall speed of the torque converter) with trans fully engaged, but with traction and no tires spinning it did NOT have enough gearing or power to move. I kept trying a few times (we were on a very tight jobsite time-schedule). I overheated the engine and trans in my desperate attempts, and was only finally able to move with the help of a jobsite crane. That's when I knew I needed the 4low-range gearing that the manual 4x4 TC had to offer. Went back to the same jobsite a year later (same conditions, same sand, same 5000lb trailer) and had ZERO issues pulling (with upgraded manual tc) in 4L. Here's my video after TC upgrade (if you haven't seen it already): https://www.youtube.com/watch?v=_1EsSxPYhXM

Here's a photo of that first fateful day... lol

Since then I upgraded to the manual 4x4 t-case, and added a trans-cooler.
Oh, and 20K and a year later my trans died. I can't complain... it made it to 230K.

None of this has much to do with your slipping transmission.. but in my case the damage I caused ultimately finished mine off a year later.

1) My first flush at 210K (after severely overheating it)
https://www.astrosafari.com/viewtopic.php?f=70&t=135177

2) Hung valve and further developing issues:
https://www.astrosafari.com/viewtopic.p ... tart=15288

3) My 2nd (and final) flush at 230K (after developing further issues)
https://www.astrosafari.com/viewtopic.php?f=70&t=138628

4) Finally, my transmission rebuild:
https://www.astrosafari.com/viewtopic.p ... t#p1515724

[zGerman]

Thank you, TransTune it is! Followed by a fluid and filter change.
But first I need to work on my oil pan, my sweet girlfriend just killed the Astro on a big rock puncturing the pan. I just dropped the front axle in preparation For the oil pan removal and found it rubbing on the pan as well. So may need some motor mounts too. So the trans has to wait a week or 10 days now.

[Mmusicman]

But first I need to work on my oil pan, my sweet girlfriend just killed the Astro on a big rock puncturing the pan. I just dropped the front axle in preparation For the oil pan removal and found it rubbing on the pan as well. So may need some motor mounts too..

Damn dude... some bad luck... and a lot of work too! Ouch!

Yeah, my oil-pan was seriously riding on and rubbing my front axle tube. Luckily it didn't rub though. Yes, new motor mounts are in order... ESPECIALLY if you went to the big trouble of pulling the front differential!

Mounts are either VERY cheap (like $5 for Anchor mounts) that will blow out quickly .. or very expensive (factory replacements). I went with NAPA mounts.. somewhere in-between. We'll see how well they last.

[tonydobbs]

But first I need to work on my oil pan, my sweet girlfriend just killed the Astro on a big rock puncturing the pan. I just dropped the front axle in preparation For the oil pan removal and found it rubbing on the pan as well. So may need some motor mounts too..

Damn dude... some bad luck... and a lot of work too! Ouch!

Yeah, my oil-pan was seriously riding on and rubbing my front axle tube. Luckily it didn't rub though. Yes, new motor mounts are in order... ESPECIALLY if you went to the big trouble of pulling the front differential!

Mounts are either VERY cheap (like $5 for Anchor mounts) that will blow out quickly .. or very expensive (factory replacements). I went with NAPA mounts.. somewhere in-between. We'll see how well they last.

Did you have problems with the Anchor mounts? Another forum member recommended those to me and now you have me wondering if I should get NAPA ones instead.

[zGerman]

New motor mounts are in order... ESPECIALLY if you went to the big trouble of pulling the front differential!

Actually to get the clearance is pretty easy. Just remove 3 bolts and let it swing down on the 4th bolt. I may write this up for reference in the proper secion, took just a few minutes.