4L60E, Hard 1-2 Shift Diagnosis & Repair 

They brought it to you because you are The Man 👍 Never could have rebuilt my 4T60E without you

I know this video is old, but I had to thank you for saving me a ton of grief. I have a 1995 Silverado K1500 with the 4L60E . It developed a brutal 1-2 shift and harsh drive and reverse engagement. I have been a mechanic for 40 years, but have done very little trans. work . I really thought that the trans was shot because it has 250000 miles on the clock. I was also told that by two trans. shops. I was going to drop the pan and check the solenoids and the 1-2 accumulator when I saw your video. My pressure was high also, and it would fluctuate if the pcm was tapped on. So I got a reman pcm for 130 bucks and viola!! Cannot believe how smooth it shifts now! Thanks again for making that video! Saved me 1500 bucks!

Excellent diagnostic skills.

How are there only 200 likes! This guy is solid!

Always great info thanks for the time you take to make videos.

Great diagnosis,Gm usually have computer issues for engine and transmission

great diagnosis Gary!

Excellent video.

This video saved me awesome information

Great video sharing

Thanks a lot! Gary👍👍👍👍

Good catch. I saw on a Transmission repai help board where one shop had a Suburban with an 4L60E with a hard 1-2 shift, but, the other shift were fine. He didn't say the line pressure, but someone suggested a weak battery would do it. Case solved.

thank you GARY

Thanks for the Time.!!!

Got a question I have a 4L80E that has zero amps on the pressure control solenoid once you drive 40ft. in gear. It has a new pressure solenoid internal wire harness, and just installed a reman ecu. Prior to replacing the ecu I had to take it on a long drive coasting with the TCC engage before the pressure solenoid goes zero. It shifts real hard. After a key cycle it would read normal 0.88amp and goes to 0.6-0.5amps while shifting. Now with the reman ecu it reads normal 0.8 amps at idle 0.6 while driving in gear. driving to a stop it goes to zero amps. Once I drive it again it shifts hard 1-2,2-3,3-4. I think the reman ecu is bad. Do you know the normal pressure solenoid amp reading while driving. When the issue occurs I can't increase the amps for the pressure control solenoid.

I need a mechanic like yourself in my area. My 1994 C1500 is running terrible and has a harsh 1-2 shift. I cant diagnose it because I lack the knowledge and experience. I finally took it to a shop and they shrugged their sholders in confusion.

If you have a hard 1-2 shift and that's the only bad symptom of transmission....is there any way you could have internal failure and need a rebuild with just that one symptom?

I have a hard ahift 1-2 but every other shift is smooth and perfect. I don't know where to start in my diagnosis....I guess battery? I need some kind of guide to check off all the things I need to rule out....

Hello I have 4l60 that was remanufactured I installed it had a hard 1 to 2 hard shift and at times felt like it was sliding into gear I installed a spineless accumulator and Corvette servo it stopped the sliding into gear and at low shifts smooth but when you hit the gas pedal I can still feel the 1to 2 shift not for sure what it is but the rest of shifts are smooth

Great diagnosis Gary! Got a 93 k1500 with the exact same issues. 160 psi line pressure at idle. This one comes to me with a new trans already in it! I have an ancient Matco Interceptor and saw at idle 1.015 amps commanded (20% duty cycle) and an “actual” reading of 1.005-1.015 amps. Getting into the “low” side of the pwm force solenoid at the pcm I measured only 400 mA, which charts out at about 160-180 psi! I even double Checked the pcm grounds for resistance issues and found none. WOW. I hate when my scan tools lie to me! “Actual current” Pffffft….Good find. What do you think causes the low current issue? Weak grounds for the driver inside the PCM. Incorrect programming? Great video.

A lot of people install a corvette servos into these and report a smoother shifting 1-2 gear. What’s your take on that?

Hi Gary. Do you think it's the same diagnosis and cure to my 604 41TE with harsh bump downshift to 2nd, and same with upshift to 3rd or 4th? It has new clutches, shift solenoid, speed sensors, T Position sensor and even the Transgo 604 valve body kit (new seal, expander, springs, corrected plate hole). Thanks.

old school van. Wait wouldn't the g30 normally have a 4l80e in it? normally the 4l60e would be in a lower trim like a g10 or g20. for example the 1992-99 suburban 1500 would have a 4l60e and the 2500 would have a 4l80e. thats odd to me 🤔

07 Sierra Classic 5.3 4l60e is shifting rough from 1 to 2 but ONLY when I drive for 30 minutes...thoughts on if its 1-2 solenoid or the trans acc piston???

we have a 01 z71 getting a hard shift 1-2 only when its hot. trying to figure it out, when its cool or cold it does not act up its totally smooth any ideas. no codes.

After today's video are they really your competitor Gary???🤔🤔🤔🤨🤨

Could the prom ever be the problem?

What cause shift only 3rd gear 6R80