1998 jimmy auto tranny problems please help

[jolly_rogger]

just bought a 1998 jimmy 4x4 auto but it has some major problems with the tranny. the tranny will only shift if you do it manually. what would cause this and how do i go about fixing this ? also the motor is running a little rough like it needs a tune up which it may verry well need. none of this is a problem for me to fix as i do alot of wrenching but i have never done anything on one of these my experience is in jeeps and older vintage cars. not that well versed in electronic trannies i have read that the tps could cause all of the problems i'm seeing but i'd like to get your opinions please. thank you all

 

[Molson02536]

just bought a 1998 jimmy 4x4 auto but it has some major problems with the tranny. the tranny will only shift if you do it manually. what would cause this and how do i go about fixing this ? also the motor is running a little rough like it needs a tune up which it may verry well need. none of this is a problem for me to fix as i do alot of wrenching but i have never done anything on one of these my experience is in jeeps and older vintage cars. not that well versed in electronic trannies i have read that the tps could cause all of the problems i'm seeing but i'd like to get your opinions please. thank you all

When doing your Tune up, replace your Distributor Rotor and Cap with a good brand like GM part or Accel ignition parts and best to use the Brass Cap insert to keep the your ignition from misfires due to arcing.

As your for transmission here are two thing that comes to mind, but you can take it to most transmission shop and have them test your transmission on a Tech2 scanner to confirm which issue your transmission has below. MOst likely you have an electrical issue to your transmission rather then a bad transmission.

1.) Transmission does not shift automatically, only manually. Swap in a known-good PCM, check wiring, check other sensors such as VSS and TPS.

2.) 3rd gear starts, can manually shift through all gears. When car has been turned off for a bit, then back on it will run normally.: VSS dropoff w/ Hi-stall converter. The rpms are too high, but VSS is showing no movement. This happens after a tire burning take-off or was stuck in snow or mud. Doesn't store a code, will not throw a CEL (It may store a code if it happens 3 or more times). Cure: Reprogram PCM for VSS dropoff -- PCMforLess knows about it.

http://www.accel-ignition.com/MMYAp...Name=1998&modelDetailName=All+Types&brandID=3

http://www.pcmforless.com/

 

[jolly_rogger]

i was told by the last owner the the upshift sol needed to be replaced so i went to pick n pull and found anout set but when i got home i found that they are diffrent the numbers on the side of the old one is 6247f and below that it looks like it says b131 the new ones numbers are 7265f and below that it looks like a 8061 plus both ends look totally diffrent. should I install these or pass and find the same number set ? thanks

 

[Molson02536]

i was told by the last owner the the upshift sol needed to be replaced so i went to pick n pull and found anout set but when i got home i found that they are diffrent the numbers on the side of the old one is 6247f and below that it looks like it says b131 the new ones numbers are 7265f and below that it looks like a 8061 plus both ends look totally diffrent. should I install these or pass and find the same number set ? thanks

Did you test the old solenoid to see if they were indeed bad. You can test them but running a jump wire from the battery to the wire leads to the solenoid and if you hear them clicking and see them working since you have them out already. Then the solenoid is good and there is a wire harness or TCM issue at the ECM.

Start with that and your 1-2 3-4 shift solenoid are bot the same. http://www.compnine.com/index.php?u...delid=6872&capuid=1&majorgroup=04&grouptype=B

 

[jolly_rogger]

okay i got it all together took it for a spin and sure enough it's f'd there is no 3rd it completly slips out of gear , had a freind whos a mec take a look realy quick and go for aride and he says it's toast and will need a rebuild. I'm just gonna pull a lower k's tranny from another one and swap it in. what models will have this tranny and are they a direct bolt in ? is there a model year range that i should be looking for ? i do not want to do any mods right now just get it moving. my jimmy is a 1998 shallow pan with a 4.3 vortec 4x4. thanks again

 

[Molson02536]

okay i got it all together took it for a spin and sure enough it's f'd there is no 3rd it completly slips out of gear , had a freind whos a mec take a look realy quick and go for aride and he says it's toast and will need a rebuild. I'm just gonna pull a lower k's tranny from another one and swap it in. what models will have this tranny and are they a direct bolt in ? is there a model year range that i should be looking for ? i do not want to do any mods right now just get it moving. my jimmy is a 1998 shallow pan with a 4.3 vortec 4x4. thanks again

Your transmission is a 4L60E, the years that you need is 1998 and newer. The Late 4L60-E transmission has a three piece case of cast aluminum alloy, bell-housing, main case, and tailhousing. GM shortened the package to 21.9" long - equivalent to a manual transmission of 15.4".

The key distinction of the Later 4L60-E (1997-2006) from the Early 4L60-E (1992-1997) or 4L60 (1990-1992) or 700R4 (1982-1989) is the six-bolt "hex" rear output or tailhousing / adapter pattern. The previous versions featured a four-bolt square bolt pattern at the adapter or tailhousing. Additionally, the removeable bellhousing is also another distinguishing feature.

The other thing also that needs to be accounted for is the Boost valve rating, make sure you have th right boost valve rating for your transmission. To hight if a boost valve rating will give you harsh D to N to R shifts from park which can cause hard parts to fail. I have a 0.490" boost valve in my Jimmy and i believe stock is 0.470" or 0.420" boost valve.

 

[jolly_rogger]

so what models am i looking for ? 1997 - 2006 blazer, astro, jimmy ? thanks again

 

[Molson02536]

so what models am i looking for ? 1997 - 2006 blazer, astro, jimmy ? thanks again

You got it, but try to get the 1997 - 1999. The 2000 and up had issues of having the the sunshell fracture when the transmission is put in to revers. GM addressed this issue by programing the ECM to drop the transmission line less then 140 PSI when engaging in to revers via through the EPC valve. Unfortunately this also causes the revers to slip if reversing with a trailer with any incline or hard acceleration in revers.

If you do pick up a used transmission here are the things your should do for a quick test to ensure the transmission is worth what you are paying for. Put a line pressure gauge (or visit a local trans shop) on the pressure test port and go for a drive to verify proper line pressure.

Base pressure at idle in P,N,OD should be around 70psi and around 140psi in R. Max line pressure should be at least 190psi at WOT in 1st or 2nd, 225psi is optimum. If base pressure is low, trans or pump is worn out and/or If max pressure is low, check EPC solenoid. If reverse is slow to engage, and line pressure does not come up to at least 130psi in reverse, replace the boost valve with a Transgo 0.490" boost valve (easy fix in pan).