therock

iTrader: (2)

My trans always had the low speed light throttle slide-bump 1-2 harsh shift and after having it modded it got worse.

I though we had it one time but it returned after a few hours of driving.

There are two categories I know of. The plain-ol'e harsh 1-2 that does it no matter the speed or throttle position, and the slide bump that is at low speed and light throttle scenarios. Say like driving slow in a subdivision looking for an address averaging 7 to 12 mph.

Mine was rude, and always seemed its worse with a first date in the truck eh?

My shop and I have been after this off and on for quite some time now.
It is believed if one addresses it like a regular harsh 1-2 with accumulator "spring" rates it will shorten the life of the 2-4 band.
The slide bump is to be addressed at the 1-2 Accumulator ""Valve". I have heard it referred to as a Regulator also but GM calls it a valve.

Well I recently had a T-converter fail and we did an accumulator "Valve" spring change in an attempt but it was a fail.
Then my input drum let go and we were back in there again and my Trans shop tried a GM TSB recommended fix and it did the trick.

She is perfect now.

Part Number 24255821
Description CONVERSION KIT, C/VLV CALN

PDF Link

gonzo 6.2

iTrader: (8)

how many miles on truck? how many times has the trans been out? Do you drive it all that hard?

I think transgo addresses this valve in there SK

therock

iTrader: (2)

70k now. Built up @ 40k. Lost a converter recently and then the drum.
My signature is a little blog on the truck.

Don't need the Trans Go Stuff. I like the Sonnax build.

She is perfect now.

The GM Part Number 24255821
Description CONVERSION KIT, C/VLV CALN
PDF Document info http://bit.ly/1sTsw6S

Tyson1972

I have a hard shift from 1st to 2nd when I"m on the highway for awhile then slow down to get off to get gas or food. I slow down then start to take off and it shifts hard as hell. I have over 120,000 on my trans, and it has the stock cooler. I'm pretty sure its the heat because I have to drive through the mountains anhd somethimes the tempo gets up to 200. That and it having 120,000 miles on it I'm willing to bet the trans needs rebuilt and a bigger cooler.

therock

iTrader: (2)

Sounds like a shift solenoid issue. I had that on other trucks before. A pretty simple and low cost fix for an honest shop or a do it yourself-er.

Its pretty common. You leave home fine, drive a while and say - get off at an exit and the first 1-2 feels like its going to break the truck. Some times a ign off and back on will help but not always.

Get her done before you break something else.

gonzo 6.2

iTrader: (8)

put the transgo stuff and a servo in at the begining,trans would never of had to come out.

gonzo 6.2

iTrader: (8)

and going into If your running a long while then come to a stop and take off and get a extreme 1-2 shift? then shut it off and restart it and its ok,then check for 1870 code.converter valve is worn out and going into limp mode giving max line pressure.Simple fix is a $35 jr.transgo kit that replaces the pulse width modulated valve to a on/off converter apply valve.So as long as your converter is still good,which likely it is.At the same time do all of the JR. kit install along with a $15 vette servo,trans will last a long time.

Tyson1972

Cool, good info Gonzo.
How long and envolved is the install?

gonzo 6.2

iTrader: (8)

2-2.5hrs for a tranny guy.better part of a day for a novice

gonzo 6.2

iTrader: (8)

I like ebay
Transgo 4L60E 4L65E Shift Kit Will Fix Code 1870 P1870 | eBay

TH700R4 700R4 700 4L60E Corvette 2nd 4th Servo Piston | eBay



a filter and pan gasket needed and possible valve body gaskets,those items are cheap