1996 Suburban K1500 - wont shift to 3 & 4
 

Hello - again -

Based upon some new info - decided to RE-post below as 'different thread' only because I don't have 'speedometer problem'. Transmission still refuses to go from 2 to 3 or 4 when in either '3' or 'D'. Will run when 'shift lever' is set to '2'. Soooo, based upon what I've read on these (and other)
forums: 1. AAMCO guy says clutches gone & need rebuilding (~$2500).
2. Local good mechanic says may be 3/4 solenoid AND/OR that since tran fluid has NEVER been changed, cud be dirt/filings/crap clogging a line preventing high-enuf pressure fluid from 'actuating' the shift into 3rd gear.
3. I have read about similar issues here; current OBDII code is P1870, suggesting multitude of possible problems. And, 4. The fluid level is up
(mentioned below) 1" higher than 'top marker' - could this - by itself - cause the shifting problem? (revised @ 1440 hrs - EDT - today - 05-10-2014)

Hello - I read all posts about the problems described here. My 1996 Suburban K1500 5.7L (w/4L60-E, I believe [I'm an idiot, so some of this may not be completely accurate] ) and heavy duty trailering pkge, trans cooler, etc. -- just recently began NOT shifting UP into 3rd or 4th gears [overdrive?]. Had driven from CT to Tucson (2500 miles pulling trailer). Got rid of trailer load & drove around out there on very crappy roads another 2000 mi; then, back here to CT on interstates @ ~67 mph. Best mileage/performance I ever had (has ~ 140K miles on it). Until 45 miles from home when suddenly engine started 'revving' as tranny wud NOT go up into 3 & 4. Fluid level was/is high (an inch above top mark on stick); but good red color. Manually shifted into 2 and drove home slowly on back roads. One mechanic said 'codes' show bad '3-4
solenoid'; but he is way to busy to do any in-depth work, unfortunately, as he is excellent man. Went to sleazy looking/acting AAMCO guy and he tells me entire tranny needs replacement/rebuilding. I now read above comments and realize there may possibly be some Electronic issue w/sensors (VSS; etc.) & NOT require the $2500 the AAMCO guy wants !!!
The 'check engine' light came on shortly AFTER the malfunction first occurred. I will get another OBC II reading from my first trusted mechanic today and write down and post here later. However, ANY help/advice/suggestions will be appreciated. THX. signed - Old Stupid Guy still w/bullet holes from SE Asia.