STILL NOT SHIFTING ALSO CALIBRATE VSSB

[ttpost]

OK HERES WHERE I AM AT, I MADE THE PARTS COMPANY REPLACE THE SECOND COMPUTER, FIRST ONE WAS DEFINATELY BAD,NO LUCK ON THE EXCHANGE.

ONCE I CLEAR CODES THIS IS WHAT HAPPENS,IT STAYS IN FIRST GEAR,NO CODES.WHEN I RUN IT TO ABOUT 32OO RPMS FOR A SEC IT SLAMS INTO SECOND AND PULLS A CODE 24 WHICH IS FOR VEHICLE SPEED SENSOR.THEN IT STAYS IN SECOND AND WONT SHIFT EITHER UP OR DOWN.
I HAVE BEEN TOLD THIS IS A DEFAULT(LIMP HOME MODE).FIRST THING I CHECKED WAS THE VSS ON THE TRANSFER CASE,TESTED IT FOR RESISTANCE IT IS WITHIN SPECS.I CHECKED THE OUTPUT VOLTAGE FROM THE SENSOR WITH THE REAR END OFF THE GROUND IT REGISTERS FROM 0-60 VOLTS AC,IT RAISES AS THE WHEELS SPIN.

ALL THE LEADS THAT I CAN TEST ARE OK.MY CHARTS SAID CHECK FOR CONTINUITY BETWEEN THE VSSB AND THE PCM,ITS OK.I DID FIND CORROSION ON THE VSSB TERMINALS FOR THE WIRE GOING TO THE PCM,I CLEANED THE CONNECTORS TO NO AVAIL.I AM BEGINNING TO THINK THE VSSB HAS GONE BAD AND IS NOT SENDING A SIGNAL TO THE PCM.

MY SPEEDOMETER STILL WORKS OK.I DO NOT HAVE A SCANNER BUT I AM TRYING TO LOCATE ONE.I TALKED TO SEVERAL TRANNY GUYS THEY ALL SEEM TO THINK IT IS ELECTRICAL,I DONT HAVE ANY SLIPPING, AND I HAVE REVERSE SO THAT ELIMENATES CLUTCH PACKS FROM BEING FRIED, I HAVE 100 MILES ON THE TRANNY,I REBUILT IT MYSELF AND IT WAS WORKING GREAT TILL THIS HAPPENED.

THIS TRUCK SAT FOR SEVERAL MONTHS DURING THE WINTER OUTSIDE.WE ARE IN A MOIST CLIMATE.DONT KNOW IF THAT HAS ANYTHING TO DO WITH IT OR NOT.

I AM PLANNING ON PICKING UP A NEW VSSB AT A WRECKING YARD TOMMORROW, AND I WILL NEED TO CALIBRATE IT.CAN I JUST USE THE SAME SETTINGS FROM THE ORIGINAL VSSB AND MAKE THEM MATCH?

MY TRUCK IS 94 WITH A 4L80E ALL STOCK(NOT FOR LONG AFTER JOINING THIS WEBSITE, THANKS GUYS,NO ONE IS GOING TO EAT AROUND HERE FOR MONTHS BUT I WILL HAVE ALL SORTS OF COOL GOODIES FOR MY TRUCK ;) ) EXCEPT FOR A FSD COOLER,

I WILL UPDATE MY SIG LINE ONCE I FIGURE OUT HOW.

I AM GOING OUT TO PULL THE PAN AND CHECK THE VARIOUS CONNECTIONS INSIDE THE COMPUTER I WILL UPDATE AFTER I DO THAT. THANKS IN ADVANCE FOR ANY HELP ROB

[ 04-29-2004, 04:47 PM: Message edited by: ttpost ]

[MTTwister]

Please lose the Caps Lock - it's really hard to read.

Wild as guess - check your shaft speed input sensors - No I don't know where they are,, yet - but corrusion can foul them and play havok (sp) .

[Turbine Doc]

Rob also break it up some, it's too difficult to read a long run on, sentence, I have the same problem sometimes when I'm POed and get on a roll.

You said you cleared codes, any more than the code 24 come back

Code F ??? look at 8th letter of vin will be F L65 or S L56 also have you gone to the RPO codes list in the members reference area, match those in the glove box to the RPO list and it will tell you volumes about your trucks set up as shipped from GM

[ttpost]

ok sorry about the run on i am poed,stepped on the shop broom and it hit the truck and scratched it :mad: i updated my sig line but it hasnt shown up yet, it is a code f, but the sad part is the rpo codes were remove from the glove box before i got the truck. thanks again for your help, now i am heading out the the shop :D i was slacking

[ttpost]

shoot i ran on again :D

[ttpost]

geez i am doing good today, nope no other codes came up just 24.

[Turbine Doc]

At least it wasn't CAPS run on, :D , hey F L65 at least you don't have EGR to deal with, don't know if you are so inclined but go have a beer sounds like you could use one or maybe 2 before you add insult to injury by dropping something heavy on your foot.

Hey JD/GMCTD what do you know about code 24s

[ttpost]

ok heres update,went out to shop had a beer(good advice)
started truck,it still runs,looked at truck (its still there)came back in looked at post,gonna have another beer and go back out and look at truck some more.
not working on just staring at it :D

ps just edited post again cause i ran on again :D

[ttpost]

went back out to shop, had another beer, climbed under truck clean.
pulled pan, fluid looked clean no burnt smell, pan was clean also.
checked shift solenoids had about 15 ohms resistance, on each one, both read the same. checked all connectors. all good.
noticed pos b&m drain plug i installed was dripping, came with nylon washer that doesnt seal. gonna take it to work and weld it on. pos

took for test drive no change.

i have also removed the vss sensor and cleaned it.

i only have two ideas, one vssb or vss input sensor?

called tranny shops two weeks to get it in, but after talking to them i dont think they know anymore than i do about the electrical which is spooky.

beginning not to trust anyone but the guys on the forum :D

forgot to tighten drain plug all the way going back out to the shop again :eek:

[C.K. Piquup]

Did you change the VSS?It is a VSS,right?I thought a VSSB was an aftermarket unit to make adjustments to readings for tire and/or gear changes.VehicleSpeedSensor vs VehicleSpeedSensorBuffer.Am I right or did VSSs becomeVSSBs at some point?My`91 is the only automatic I own(with a computer).Did you replace the module in the trans?GM says,when you change module,change ECM.You say you changed ECM.My`91 has VSS(2 seperate parts)in trans(4L80E).I`ve gone into failsafe(limp-mode/2nd),scanner said variation between speedo reading and tire speed(everything stock).Bought both sensors,laid on seat,working fine.Now,months later,doing it again.When towing last weekend and yesterday after leaving hiway.Speedo doesn`t work when in failsafe.I`m going to replace VSS(2)now.

[charliepeterson]

These 4L80's have sensors for input and output speed. They can be interchanged for diagnosing by removing one screw and pulling out.

[ttpost]

ck pickuup heres what i know, the vss output sensor is on my transfer case, it screws in like an water temperature sensor for a 4wd, on a 2wd it is on the output shaft.

my charts say check the resistance at it should be about 20 ohms disconnected. as i understand it if it is not working i wouldnt get a signal to the speedometer, i am getting a signal.it puts out ac voltage to the vssb which should be 0+ volts as the speed increases,i tested this by blocking the wheels, jacking up the rear end and putting it in gear and increasing the speed. my comprehension is that it is bascically a little ac generator.

the vssb(little white box under the glove block) distributes the the current to the aldl,speedometer and the pcm. which governs the shifting points. i am still learning about this, so i may be wrong. mine is a 94.

from some information given to me on an earlier post of mine i got a link to another site which tell you how to adjust it for different gear ratios and tire size

also someone also said to remove and check for metal shavings, mine had a few but not much i cleaned them.


also i called my local auto zone dealer was just going to buy another, what the heck 25.00 right. well the one i have is 67.00 because it screws int and doesnt have a bracket that holds it in.

i believe you have a ecm (electronic control module and i have a pcm(power controll module) i dont know if that makes a diffence.

i am not a mechanic by trade, but due to economics i am being forced to learn this stuff :eek:

would rather be working on a camaro :D

[ttpost]

charlie, the vss on the rear screws in the one on the front bolts in, both checked out with the same resistance, so i assume the input sensor is good.
:rolleyes:

[ttpost]

sitting here trying to remember why i bought a diesel :D

oh yeah the deer and elk think i am a logger so all i have to due is shoot over the hood of my truck :D

[C.K. Piquup]

I hear your woes.I think the problem is more to do with computer controls(love`um working/hate`um broke).Anything w/4L80E can do this.I`d be happier with a TH400/GearVendersOD.Plum Simple.I love my many`67-`72 GM trucks.Gotta keep them anyway to have something to go when the newfangled won`t.My`95 now has MFI with a cable that links my right foot to the injector pump,primitive yet effective,go figure.It`s also a manual trans.Although the scanner isn`t always conclusive,it is definitely the way to go when you can`t dope it out yourself.Got any buddy mechanics to scan it for you?

[Cowracer]

Replace the INPUT shaft speed sensor. It will not be on the t-case, it will be north of the shifter shaft on the side of the tranny. It is a proximity type sensor, and can be malfunctioning even when showing the same ohms as a good one.

I lived this EXACT problem.

Tim

[cruzer]

Granted my truck is a 92, I had the rear speed sensor go bad and it went into limp mode. I lost 3rd & OD and shifting was hard, also lost speedo.
Rear sensor =speedo. I replaced the sensor, but I still had the same problem until I remembered what a Mr. Goodwrench said,"you may have to reboot the computer by disconnecting the batterys". The trans worked fine after I did that. Frt and rear sensor should be the same part and they are on the drivers side of the Trans.

After rebuilding the engine, another problem I had was the throttle position switch was not calibrated correctly and the trans had the same symptoms except I did have speedo. My switch is on the pump because of mechanical inj. You probably don't have this switch, but I figure any little bit may help. Good Luck!