ok so I have been searching for the most likely cause of my harsh shifting. I found this:


"1-2 shift is delayed and harsh, may not shift into Over Drive CheckThrottlePosition Sensor (TPS).for smooth and linear electrical response over the entire range of motion. If not, replace. "


I have tapped the wires with a multi-meter and tested the voltage through the throttle range slowly and it seems to move just fine. The voltage reading did not fluctuate at all from no throttle all the way to full throttle, I did it 3 times.


I plan to replace my 1-2 shift solenoid and I have already purchased a new one, I was just curious if anyone has any other ideas of what may be going on?


its a 1999 gmc jimmy 4wd with the 4l60e of course.
The shift from 1st to 2nd seems to take longer than it should to occur, and when it does it just kind of shifts instantly with no torque smoothing or feathering. So the shift is very abrupt. I almost think that 2-3 is a bit rough, but it isn't anywhere near as bad as 1-2.

 

Read this.

Playing TAPS on Pressure Systems - Sonnax

http://www.sonnax.com/articles/241-2...-modifications

Transmission shop should be able to diagnose your shift problems VERY easily using a scan tool.

If you want to try to do things yourself, Car Guage Pro / Car Diagnostic Pro will display the Tap cell info discussed here but does not have full functionality for resetting the adaptive learning. You reset it other ways. Get a GM factory manual to understand things.

Worst case, you could have a valve body modified to compensate for bore wear in the valve body - a common problem with 4L60e. I recently had my trans "rebuilt" after the sun shell stripped and I think they (a National Trans Shop) simply put an old hi-mileage rebuilt POS in it that has a modified TCC regulator valve in the valve body and old-style TCC lockup converter. Mine originally was ECCC for the Torque converter clutch operation and now it locks up to zero slip and all shifts/TCC applies are quite harsh at all throttle angles (and even low tap cells). Has all the gears now, but shift quality and smooth TCC operation has been effectively destroyed. A great job for $2350! As soon as Winter is over, the Blazer will go back to them (3 year warranty). Don't know how far I will get but they are going to know I am not happy with the way it works.

 

wow that's ridiculous. I am hoping to avoid having to spend that much since I didn't spend much more then that on this vehicle. You gave me a lot of information I did not know about and I plan to read through that. I will also look into a shop just scanning and seeing if they can tell me what is going on instead since that is much simpler.
thanks for the information, and gl with dealing with that shop!

 

I already talked to the trans shop right after taking the vehicle. They talked me into giving the PCM time to adjust shifts to the new trans (the adaptive strategy in the articles). Sounded like something I should do, but it's been about 500-700 miles and it's not better yet. Makes me irritated most everytime it shifts.

 

I ended up installing the 1-2 shift solenoid and it now shifts much better. Under moderate acelleration it is crisp, but not harsh and way late like it was all the time before. I'd say it's as solved as its going to be

 

My Blazer has been slamming the 1st to 2nd gear upshift for a couple of years now, it's worse when cold. The transmission works great besides that. Was it hard installing a new shift solenoid? I presume you have to drop the trans oil pan.

 

honestly it is not hard at all. Yes you do need to drop the transmission pan. The job is honestly just messy but I would say difficulty is no different than changing oil. I have never dropped a transmission pan before, and this job was probably 3/10 difficulty at the most.


1 bolt is a little hard to turn but not hard to reach, it just has stuff in the way so you want to have a pretty small 10mm wrench. the smaller the better for that 1 bolt. If you have changed your oil you can change the solenoid.


I can give you some pointers if you want, it is really a straight forward job and sounds a lot more scary than it is. Everything is very easy to access. No hard reaching, or long funky ratchet extensions or anything required for this job. I used an extension for the pan bolts.


The tools I used were:
3/8ths ratchet
an extension (anything probably 4-5" or longer should be fine)
13mm socket (I cant remember if it was 13, 14, or 15mm for pan bolts)
10mm wrench (smaller the better) (this is used for only 1 bolt)
10mm socket for the other 10mm bolt that you don't need to use the itty bitty wrench for.
small flatblade screwdriver or a pick tool with a angled tip or hook may work.


that's all you need other than:


wheel chock for rear wheels
jack stands x2 minimum to keep front of vehicle up safely in the front
I used a floor jack as a failsafe support on the frame behind one of the jack stands (my dad was almost crushed by 1 jackstand that failed, luckily the other didn't.
I also disconnected my negative battery terminal because I am disconnecting an electrical connector for a solenoid and there is trans fluid everywhere, I don't want anything shorting out or whatever, so to be safe, I disconnected my battery.


1) jack the front up, chock the wheel, support the vehicle safely so the front end is off the ground


2) I recommend putting down a cardboard box flattened out on the floor unless u want to clean up tranny fluid


3) have an oil pan ready (the trans fluid I drained would have fit into 1 typical oil pan but since I had 2 available I put them both down there. The trans fluid will not drain in 1 specific spot like when you drain oil, it wants to run down the frame and go all over the place. So having more than 1 pan, or a plastic bin or something with wider coverage area will help you catch more of the fluid.


3a) to help make less mess, once the pan is fully unbolted, try and get 1 corner of the pan dropped lower than the others as much as possible, so it will focus the spill into a single stream, until you get the pan all the way off, you will not be able to drain every drop. During this job I drained around 4 quarts of trans fluid.


4) with the transmission pan off, the large plastic black thing there is the transmission fluid filter. It literally just pulls out, it uses a friction fitting on the pipe. if you are not replacing the filter, you do not need to remove it.


4a) if you do replace the filter, when you are reinstalling the pan make sure the filter is rotated so it can be pushed up all the way or you will get frustrated wondering why the pan wont seat properly when reinstalling it.


5) To remove the shift solenoid for 1st to 2nd gear (the one closer to driver side of vehicle) (they are right next to each other):


5a) unplug electrical connector, Then using the flatblade screwdriver or pick tool, there is a metal clip thing in a slot that acts kind of like a c-clip. When the solenoid is pushed in, the metal clip is then pushed in the slot which retains the solenoid so it cant come out. You will pry this clip out and it should come out pretty easily. Once that clip is out, the solenoid pulls straight out (don't pull it down towards the ground, it is inserted into the side of the valve body) When you pull it there is a little shaft thing and spring that may want to fall out, mine didn't fall out but I pushed them in with my finger and they kept acting like they were gonna come out. It isn't much more spring pressure than a click ball point pen.


5b) when you insert the new solenoid it may have a different tip on it with a screen filter, this is ok, just push it in over the spring and shaft thing that are in there. once it is in all of the way, insert that metal clip thing back into its slot. Then connect the electrical connector.


*note*


if you are replacing the transmission fluid filter you can do it at literally anytime during this entire procedure once the pan is removed regardless of whether or not you are doing solenoids.




Now for the transmission pan info:


6) remove the old gasket from the transmission pan carefully to remove as much as possible (so you don't leave a bunch of residue)


6a) to remove traces of old crusty gasket that get stuck on the pan, you can use a very mild scotch bright, flat blade screw driver or gasket scraping tool, etc. Acetone worked pretty well, I don't know if engine degreaser or anything else may be stronger (maybe someone can chime in with a better solvent) If you use acetone I recommend constantly adding more acetone to your scrubbing tool of choice.


*note*


you want to do everything in your power to avoid putting deep scratches or gouges in the metal here. I used a razorblade to try and scrape the gasket and found it easily cuts the metal, so just be really careful when you are cleaning this area so the new gasket will not leak.


6b) Your transmission pan may have a square magnet glued at the bottom that is probably coated in a slimy metallic grit. You can clean your transmission pan however you like, but I strongly recommend cleaning the inside, and the gasket sealing surfact thoroughly so you are not putting more debris into your transmission. Take your time on this, its not hard, it is just time consuming and messy.


7) aligning the gasket and the pan is an interesting task. the holes in the new gasket should be just slightly smaller than the screws which means if you thread a few of the bolts in the gasket will hold them in place, and this will hold the gasket onto the pan in the proper place.


8) reinstall the pan with the gasket attached using a few bolts. You will probably have to pull/rotate the cable linkage thing out of the way to get this pan back on (or even off) this is ok, just try and move it only enough to do the job.


9) add more transmission fluid


9a) I recommend strongly, having a good measurement of how much fluid you drained. As long as you add exactly this amount (as best you can) you should have no problems at all. Obviously some fluid will spill on the floor and such, but if you add how much you know you drained you can always add a tiny bit more if the dipstick is showing you are lower than you would like to be.


9b) you use a funnel to add the transmission fluid into the transmission fluid dipstick hole


9c) check your transmission fluid level with the engine/transmission fully warmed up (this is why you want to put in as close to exactly as much fluid as you drained as you can) if you are just a little bit low that's fine, if you put in too much you need to lower the pan again to drain fluid out (pain in the *** compared to adding a little more until it is properly filled)


Basically at this point you are done, when you are checking the trans fluid the dipstick hole may be coated in fluid making it really annoying to get a good dipstick reading. So just leave the truck running and check the dipstick like 50 times until you finally get a defined line of fluid on the dipstick so you know where it is. It should be inside the hashed area of the "hot" area on the dipstick. as long as you are in that range you are fine, it does not have to be at the top of the hash line.




I tried to make this thorough and clearly written so if you have questions you can reference this. If you have more questions feel free to message me.


Honestly this job probably sounds a lot more daunting than it really is from how long this all is. I promise it is not hard and if you have done an oil change including filter, you can handle this. I personally did it for the first time, so I dedicated a Saturday to working on it that way I didn't care how long it took. I spent a few hours.


-regards
justin

 

Great write up, thanks for the info. My truck is coming up on 50k miles since I last changed the trans fluid and filter, definitely going to replace the solenoid next time I'm in there. It'd be a much easier job if they had fitted a drain bolt at the factory.