My 2000 blazer has had an issue recently with the transmission. First, it shifts hard into second. But the weird issue is it seems to keep the engine right around 2000 rpms under light to moderate acceleration. I mean, 1-2 shifts at like 1500 under light accel, but 2-3 occurs at 2000 which drops rpms to 1800, then shifts 3-4 or what feels like 3 1/2 which again drops to 1800, stays there while accelerating, then softly shifts into overdrive. It shifts soft after 2nd gear. It kind of feels like its slowly engage gears, but I don't think it's actually slipping. Also, when I want it to downshift, it takes a bit of pedal, and even then it dropped in to 3rd then went right back into 4th, without me moving the pedal. Is this a problem? I'd like to fix this before it starts wearing parts out. Any ideas? Thanks In advance!

 

This is a known issue with GM vehicles that have the 4L60E transmission. The issue normally presents itself after the transmission has had time to warm up and has been driven approximately 50 - 60 MPH. At highway speeds the torque convertor locks up for increased efficiency and so that it generates less heat. The lockup is accomplished by a solenoid in the tranmission's valve body which applies th...e torque convertor clutch (TCC). The solenoid and valve body itself are made of different metals which cause them to expand and contract at different rates. This constant variance in rates causes the valve body to wear away. The wore valve body allows transmission fluid to slip past the solenoid, causing a weak TCC apply. This weak apply is detected by the tranmssion as a slip. When a slip is detected the computer increases the line pressure to the shift solenoids to make the shifts firmer to minimize damage. This increased line pressure is what causes the hard shift that you feel, it is most noticable from 1st to 2nd gear. If the transmission detects the slip on two consecutive trips it will illuminate the "Check Engine" or "Service Engine Soon" light and store the code P1870.
If you ignore the problem, you will end up damaging your transmission and it will require a rebuild or replacement. However, if you catch it in time you can generally save your transmission. There are two ways to remedy the problem. 1) Replace the valve body (GM has a new updated one) 2) Repair your current valve body


Just had this issue with mine and had the valve body rebuilt.

 

Damn Bre way to lay it out there and school us all!!!

 

LMAO thanks! But alas....I didnt write that because I would never be able to explain it that well. I was told I needed a new/rebuilt Tranny and knowing what I know I was like NO FING WAY I AM GOING TO ACCEPT THAT without some checking first! I told my guy to check the solenoids and valve body, also the clutch but that I REALLY didnt think it was the clutch because there was no evidence of wearing...(my hunches are usually right with my truck) he told me no one would do that for me (he doesnt usually mess with transmissions), I was getting a 1870 code and they will only rebuild the tranny, they wont check anything else....I convinced my friend/mechanic to check it out, I believed he could do it LOL...so he found NO metal in the pan, no wear to the clutch, tested the solenoids and they were fine, relized this was happening to the valve body as I suspected.

HE is awsome for listening to me and I saved myself over 1200 bucks! Frist job I have not done myself because I am a weakling

 

Can't thank you enough for that very helpful response. Full of great info! I'll check into that ASAP, it's driving me nuts! Lol.

 

No prob! Glad to help
Got mine back today and she's drivin great! On to the next issue lol!

 

I have the same trans in my truck just ealier model 94 and it has the same issue.I flushed the fluid and put fresh in along with a bottle of lucus.Temporary fix for now till I can get my Jimmy on the road.

 

Would anyone advise against putting additives in the transmission for now, as a temperary fix? I've heard both good and bad things about Lucas, I really don't want to burn up this tranny, the truck only has 142k on it! Thanks

 

Lucas is ok but like 1sttime said I would have it flushed first just to get the old fluid out and then try adding the lucas.

 

Ok will do. Thanks