sambroom

Video of the issue here

Hi I'm new to the forum. I've scoured the web and can't find a lot of info. I have a 2008 Chev Avalanche with the 6.0. I get an rpm flare at downshift from 3 to 2 under load only (pulling my boat up a hill, or if I'm getting on the throttle) no other issues and no codes. I dropped the pan last night, no black stuff, no burned fluid, only a little fine metallic "slime" on the magnet. I was going to just replace the fluid, filter and the 3-2 downshift solenoid, but it was such a pain and mess to drop the trans pan, I want to make sure I get this thing solved the first time around. So what other parts should I be looking at? Upgrades I should do?

Brandon Sloan

In your post you said you are getting a 3-2 downshift shift flare but also state only when towing with a load. Your also stating that it happens when pulling uphill as well as getting on the throttle. This would be two different concerns. The 3-2 Downshift solenoid and valve train in the valve body in earlier versions of the 4L60-65-70 transmission had issues with the 3-2 downshift control valve spring breaking. That would be what i would be inspecting for a downshift concern. it would also cause a tie up in the gear change under normal driving conditions as well so its hard to diagnose without driving the vehicle myself. Now onto the 2-3 upshift shift flare, that could be anything from a worn 1-2 accumulator valve in the valvebody or the 3-4 clutch apply circuit could have a sticking check ball, which is common with 75,000+ miles, or the 3-4 clutch itself is wearing out. If if were mine, which I've rebuilt the trans in my avalanche, I would have a complete overhaul done before it gets worse. I would upgrade the 3-4 clutch from stock to a 14 clutch Zpack from reybestos, modify the torque converter regulator valve to command full lockup, upgrade the 2-4 band to a wide band, install a corvette servo, and put a shift kit from sonnax or modify the accumulators with upgraded new aluminum pistons if the builder knows what he's doing. These are my thoughts on attacking the symptoms your having. I've been working for GM since '98 and have been a professional transmission builder for the last 6 years if you are interested in knowing my history.

chevyfansince85

Brandon it sounds like you really know your stuff. I have an avalanche with the 4l60e in it and I had a very similar problem but I kept driving it until it finally said no more, lol. Anyways, I am going to replace my transmission and a local shop near me that I haven't been too before quoted me 2900 for the full rebuild. However, I don't know a lot about this stuff and I read this article on getting your transmission rebuilt versus purchasing a remanufactured 4l60e. I've looked around a bit and it seems that I could have one shipped to my mechanic for around 3300, obviously that doesn't include labor though. Just curious as too if you've heard about any significant differences between the two transmission types and what I should do. I'm looking to keep it for the long haul as a work truck in the future so I need it to last