Sounds like lots of transmission knowledge here,
It's in a 2000 Chevy 1500 express van but my L460-E upshifts fine upon heavy acceleration but driving around town and not putting it to the floor, 3rd gear slips bad. I had a hairline cracked/ leaking torque converter replaced 3 months ago.....if the clutches or pressure is bad, hell I could have replaced the trans complete for another 500 bucks....any advice?
Thank you

 

It's a 4l60 not a l460, is there a question in your post?

 

Any trouble codes such a P1870 for slipping?

Rick

 

Yes ....the code meant " transmission slipping"I had a torque converter replaced 3 months age due to a leak( hairline crack in converter). The trans shifted fine throughout all gears ( no slippage.) before repair. Since repair , overdrive kicks in sooner than did with The original converter ( 35mph) a mechanic told me it shouldn't kick in till 45mph. A few days ago the trans began slipping going into 3d gear. I've always driven the truck easy as no reason to beat the he'll out of a work truck. Trans has never been run low on fluid even when it was leaking. I noticed when I stomp on the pedal ( to the floor) all gears work, no slippage but as soon as I drive it easy and let it shift into 3rd at lower rpms the engine revs up ( slipping) A mechanic told me the 3rd clutch pack is worn/ blown however I've never seen a blown clutch pack that works then doesn't than does when I put the coals to it.
I spent $1150 bucks replacing the converter and for about another 400bucks,I could have had a rebuild with a warranty. One mechanic says it's the clutches,another says its the shift module and a third says its a solenoid in the valve body. It had a code which meant ( transmission slipping). All is know before torque converter replacement that the trans worked fine. I can't find a ID tag on the trans . It doesn't have a button where as you can turn the overdrive off, ( just the 1,2,3,D positions on Need an opinion from someone who knows their stuff as w three different opinions I don't know who to trust.. If the 3-4 clutch pack is blown, I wonder if the low rpm shifting into overdrive caused it. to wear out. I'm no idiot ( I hope) as if there was any slipping, delayed shift or other problems with transmission, I never would have done a repair instead of a replacement. I don't have teach however when speed shifting I'm sure it doesn't slip.
Thank you

 

For me, it was recently last month the 3-4 clutches worn out and a P1870 code with RPM's climbing due to slippage if I could get it into 3rd gear at all. The rebuild is now complete and runs well.

For me, with 2.73 gears in the differential, yes . . . I probably pushed this trans to burn up the 3-4 clutch pack. I was in OD at a low speed in my El Camino which I'm told, on an already well used transmission, could put too much strain on the 3-4 clutches. Apparently, there is not a lot of apply pressure in these clutches in OD. The rebuild guy said that with new clutches, OD might not be a problem for a long time and a lotta' miles. But he thought running around town mostly in D3 would be a good plan. It all makes sense to me.

And D3 is probably not loading down and lugging the motor quite so much. I drove around for a few weeks saving up bucks for the rebuild in a manually shifted D2 with no additional harm done. I think I hit 3500 RPM max running at around 50 MPH or so in D2.

Rick

 

if 3rd is slipping you need a rebuild. Time to pull the trans. Have fun.