1995 G3500 5.7 4l80e Shifting Issue (vss?)

[UBCVan]

Have less than 55,000 miles on this G3500 Rally w/ 5.7 and 4L80E. (Church van bought new, so lots of stop and go). The past couple of weeks it has randomly started to shift hard. It would be hardest from 1-2, but 3 and 4 were hard as well. You would drive fine, then you would get the SES light to come on and a minute or two of hard shifting, then the SES would go off and it would be fine. Has been 90% driving/shifting fine with no SES light, with that random 10% hard shifts and SES light immediately coming on. Just a couple days ago the SES has stayed on. Shifts hard all the time now. Pulled the code and it is 43 (OBD1) which means Knock Sensor? That doesn't make any sense to me. What do you think? The fluid level was fine and looked/smelled fine, but I still dropped the pan and did a filter kit today. No change. Also it downshifts seamlessly, and it doesn't pop out of any gears or slip anywhere. Even highway speeds it stays in OD no problems.

[gmtech4]

i have to rip you for changing the oil and filter in attempt to fix it ,tisk tisk!!

 

anywho,for whatever reason,the programing tells the transmission to go to max line pressure during the knock sensor code tripping,

 

get the truck diag'd or replace the knock sensor in another hail mary attempt(nun pun intended) lol

 

the knock sensor goes into the block drain so be carefull of the coolant,

 

sounds like a nice low miler truck,what did ya pay for it?

[UBCVan]

i have to rip you for changing the oil and filter in attempt to fix it ,tisk tisk!!

 

anywho,for whatever reason,the programing tells the transmission to go to max line pressure during the knock sensor code tripping,

 

get the truck diag'd or replace the knock sensor in another hail mary attempt(nun pun intended) lol

 

the knock sensor goes into the block drain so be carefull of the coolant,

 

sounds like a nice low miler truck,what did ya pay for it?

 

Thanks man. Actually this is still the Church's van. I am just one of the drivers and only one able to do mechanic work. I wish I had googled how to read the codes before messing with it, otherwise I'd save myself the trouble. Oh well.

[exracer]

had same issue with a my 93...tranny shop diag it as time to rebuild the trans....they did and after 8 repeat tries the trans was the same? and they gave up

 

...on my own I tried a 30 buck used computer and now works perfect

 

seems the old puter comanded high line pressure when it felt like it..lol...or it had a bad ground as I cleaned them up at the same time

[UBCVan]

Hmm so I finally replaced the knock sensor today, unplugged battery, and fired her up...just to see the check engine light come back on. Starting to think I will do what exracer did. Maybe a new ecm will fix the issue I dunno. Same code 43. I cleaned up the connection and everything. So I dunno what to do really. Should be simple to me but its seemingly retarded lol.

[exracer]

curious as to you ever solved the problem?...I know I spend a lot of wasted time and money on the call of a "Professional" Trans shop for nothing........shifting funny? hard or inconsistant shift points should always be checked out with a tranmision scanner before they give ya the old "Yeps she is junk and we can rebuild her to be like new again..lol

[alpha capo]

curious as to you ever solved the problem?...I know I spend a lot of wasted time and money on the call of a "Professional" Trans shop for nothing........shifting funny? hard or inconsistant shift points should always be checked out with a tranmision scanner before they give ya the old "Yeps she is junk and we can rebuild her to be like new again..lol

 

 

i got a 96 with a 305 and i just had a issue where the engine was racing....i knew it was a vacuum leak. and then about a month or so later it kept getting worse and then all the sudden the tranny was shifting very hard....so i took it in.

 

the Throttle position sensor was replaced and that fixed the trannny shifting hard problem. wich is cool becasue i thought the tranny or possible the clutch itself was going bad.

 

i was hoping the vacuum leak was due to that crappy heater core hose that plugs into the manifold ..but replaced that and still had the problem

the vacuum leak was the upper and lower intake manifold gasket back by the distributor....and that solved the high idle... Lean mixture condition.

 

now she runs smooth and shifts like buttah.....i did the cap rotor plugs and wires why i was at it...also a new water pump....now all i need is to get a new hose for the power steering because its leaking too.