98 K1500 hard shift 1 to 2 when hot

[inthechateau]

Had event today never experienced with my 98 Silverado. Has 5.0 with 4L60 with 130K on the clock. After driving about 30 or so miles noticed it starting to shift hard into 2nd from a stop. Rest of shift cycles seem fine. Cooled down and took it out and shift is fine but I do not feel the converter lock up and when cruising steady speed with pressure on the throttle and tap brake the RPM does not increase for lock up drop out. Have not pulled pan yet, just hoping for hints to look for.

Thanks

 

[someotherguy]

Possibly two separate issues. Failure to lockup the converter could be as simple as a bad brake switch, even if your brake lights still work (there are multiple contacts in the switch, and they tend to break over time.)

The hard 1-2 shift when warm is likely going to be result of a P1870 code (component slip) and so the line pressure is bumped up full to prevent the slip and save your transmission. Check your codes, if P1870 then do some searching on it. Very common cause is wear in the valve body at the TCC regulator bore will leak past the piston. There are kits to repair it (steel sleeve) though the reamer tool makes it a little pricey for a one-time DIY job; but any honest trans shop can do it for you, or they may recommend replacing the valve body instead of repairing yours.

Richard

 

[inthechateau]

No DTC yet, just started to act up the other day after a long hot day drive. Been pulling a lot of trailers lately. Going to check brake switch first for TC lock up issue, replaced that switch when I put truck on the road last yer. Aftermarket junk as usual. Pull pan after I get my weekly mowing done this weekend, course this is the weekend I have National Guard duty too so there goes the weekend. Thanks for the hints and will post pic's and or results as I go along.

 

[inthechateau]

It finally popped the 1870 DTC. Ordered a rebuilt VB from Ken Partin Transmissions http://kenpartintransmissionparts.com/ . Very nice guy to talk to and great price ($159.00) See how it works out, He says it will give me firmer TC hold too. We;ll see

 

[Jeff Davis]

Did you ever get this fixed?