Harsh Shifting

[gsal86]

I have been peeking arround the internet trying to discover what may be causing my car to harshly shift fron 1st to 2nd and then from 2nd the 3rd. One solution some one had was to replace the:

"TPS (throttle position sensor). The other reason for hard shift is a worn Boost valve and will need to be replaced, or a faulty transmission fluid EPC (electronic pressures control valve). Both Boost valve and EPC are located in the Valve Body and can be replaced with out dropping the valve body, but have to drop the transmission pan"

If anyone could confirm or deny this replacement as necessary that would be helpful. I did just recently top off the tranny fluid because it was running a bit low but there is no leak....

Thanks

[GregGP]

This topic is covered extensively here http://www.automotiveforums.com/vbul...d.php?t=920671 Basically, you should install a shift kit and that will probably solve your issue. Here is the shift kit that I used on my car, I have had it in there about 2 years without any more problems. http://item.mobileweb.ebay.com/viewi...assified=false hopefully that link works. If not, just search for "transgo 4t65e shift kit". It's about 60 dollars on Ebay.

[Tech II]

"TPS (throttle position sensor). The other reason for hard shift is a worn Boost valve and will need to be replaced, or a faulty transmission fluid EPC (electronic pressures control valve). Both Boost valve and EPC are located in the Valve Body and can be replaced with out dropping the valve body, but have to drop the transmission pan"


You don't access the valve body by dropping the pan, you have to drop the side cover.....

Harsh shifts usually occur when a code has set, and the PCM is commanding full line pressure.....has the vehicle been scanned for codes?

You don't give the mileage, or state if a transmission service has ever been done....

[gsal86]

Thanks GregGP. As for the millage it is aproaching 200K and I actually replaced the entire transmission about 2 years ago with a friend of mine. So as far as a transmission service it was quite a service for sure! So the fluid is 2 years old since I put in new fluid for the transmission. The transmission I put in had 80K on it so it probably has 100K on it by now.

Greg

[la1]

I was getting harsh shifting after running for awhile. I would also get a random "thump" when starting out, like the trans was trying to shift. My downstream OX sensor soon failed. Installing a new downstream ox sensor alleviated a lot of the harsh + the thump now and then. I took out the other ox sensor and cleaned with sensor safe TB cleaner. It ran strange for a day or so till the PCM got used to it. now no harsh or thumps. I am left wondering if I could have just cleaned the downstream. Glad I kept it, will try sometime. oh yeah the PCM was throwing no codes.

[Tech II]

If the downstream O2 sensor failed, how did you know if it didn't set a code?

All that O2 sensor does, is report catalytic efficiency......it would not cause a bump or cause harsh shifting...

[SulkierLizard]

Do you think it's possible to send an OBD II command to reset the code when it happens? I just installed the shift kit today. Looking forward to no more harsh shifting.

[DrRadar]

Checked out GregGP's link and it's great info. PDF'd it and filed for future reference.