i've searched the forums and read every thread i could find about tranny problems .here's my problem .......engaged 4wd drove for maybe a mile or so then disengaged.4wd seemed to be stuck . fixed that now 4wd works fine but since then the tranny shifts thru 1st and 2nd fine but slips in 3rd and 4th . reverse is fine . dont notice any slippage in the gears that work ....i am thinking it is electrical because it started all of the sudden ....changed fluid and filter fluid smelled old and didnt have any unnatural color or debris in it ..i have rebuilt plenty of th350's and 700's so i know enough to still be wary it may be smoked 3/4 clutches .
1996 blazer lt 4wd
4.3 vortec
4l60e
ps...i've already installed the PCM ground fix jumper ......if i have missed this problem somewhere on the forum i'm sorry and a point to the thread would be appreciated

after doing some more checking i cant find a connection problem ....did a scan and only code that came up was a P0300 random misfire . no tranny codes . also with a slow acceleration past 2nd it seems to engage 3rd ....could be wrong might just be kicking down . seems to happen around 3000 rpm .

 

ive heard a p0300 code can cause tranny shift problems

 

ps...i've already installed the PCM ground fix jumper

Point me to the "HOW TO" to do this . I have never heard of this

 

Beginning at the start of production for all 1994 model vehicles equipped with the THM 4L60-E transmission, there was a VCM (Vehicle Control Module) installed on the vehicles with an internal ground wire that connects the two printed circuit boards together. Some vehicles with the VCM will display very erratic and unstable line pressure rise in the transmission, and in some instances, premature failure of the transmission. Bad ground connection from one printed circuit board to the other.
There is now available from OEM parts sources, a new service repair kit with an instruction and is available under OEM part number 12167310.

GM Bulletin Number 66-71-03A
Harness jumper wire and instruction kit P/N 12167310
the part kit is available from the dealer and was $50.13 at last check and only applies to certain PCM's the problem was fixed in late 1996 from my understanding .

 

Oh, post '96 tranis are OK. That's good. Nobody has Pics of what this $50 kit really is? The $50 kit probably makes it really idiot proof. Has anyone really looked at the boards enough to see where jumping from ground lug to ground lug would do the job for Pennies?

 

I have a 99 4x4 as well and I lost 3rd & 4th while towing a small boat down the highway last year. 1st, 2nd and reverse were all that remained. Had to replace the tranny with a rebuilt. Wasn't cheap either. Am now afraid to tow anything at all.

 

This is the same problem i had about a year ago... More than likely it is the clutches.. When I took mine to my tranny guy he siad it was the solenoids and th eclutches, He replaced and bam everything worked great.

 

the kit is basically nothing more than a 10" piece of wire with the proper metal connectors for the plug and a set of instructions that explain what wires to move and where to install new wire .......they also say you need two special tools to do the repair .......one for releasing the connector from the plug and one for puncturing the seal in plug .

since 1-2 shift works and the 2-3 shifts tries ...i'm thinking its the clutches that are bad .....700R4's were notorious for burning up the 3-4 clutch packs. the 4l60e is an electronically controlled 700 so i expect it would have the same basic hard parts problems.

i'm thinking more towards buying a jasper rebuilt tranny ......anyone with experience with one?....is it worth it or should i rebuild myself with hand picked parts ?

 

Yeah, that's basically the gist of the TSB.

As far as the difference between a Jasper rebuild and rebuilding it yourself. You'll likely use better parts than Jasper, but unless you have had experience in rebuilding these transmissions or have someone there with you having said experience, there are a number of ways that things can be screwed up in the rebuild process.

 

i've rebuilt plenty of th350's and 700R4's .mechanically they are the same so thats not a problem ....what worries me is if i rebuild the tranny or buy a rebuilt is that i havent found an electrical problem that will cause the same thing to happen again .
hence my main concern for verifying all electronics related to the tranny are working properly or repaired before i replace the tranny itself .