Transmission SOS, Multiple Codes and Grinding Sound

Hey TW,

Short Story: I recently removed my transmission to replace the torque converter, input shaft seal, and filter.
Upon startup after putting it back together, I get the following codes: P0974 (Shift Solenoid A - Circuit High), P0977 (Shift Solenoid B - Circuit High), P2716 (Fluid pressure solenoid D electrical), and P2759 (Torque converter lockup clutch electrical fault).
I also get a pretty severe/loud/shouldn't drive this thing sound that most closely resembles a starter solenoid not retracting from a flywheel. Based on the timing of the sound after startup, I don't believe that's the issue, but I could be wrong. The sound does become quieter and eventually goes away after about 2 minutes. I have a video of it here: https://drive.google.com/drive/folders/1-OL8uDgpOOazjLDnbIs44LqR2Jcb7Dp2

I'm looking for help and feedback on how to get my truck back on the road.



Context: I'd like to think I've got my together when I'm working on my truck, but I think I've royally messed up this time. For context, I converted my PreRunner to 4x4 in October 2021. I was and still am super proud of how that work turned out and love the added capability of 4WD. I put in a transmission that I got for cheap before they became hard/expensive to find. When I put it in, I followed the SOP on R&R'ing the Transmission, used MaxLife ATF, followed the fluid level check procedure, replaced the filter and the SLT solenoid and I was on my way. Shortly after I got a slight grinding sound when in gear (No CEL). It was brought to my attention that it was most likely a bad stator 1 way clutch in the converter, so I pulled it and replaced it with a TC Reman unit using the same procedure. This time the new torque converter would make an occasional "rattlesnake"-like hissing noise during lockup but I didn't think anything of it. After about a year of all kinds of wheeling, long highway miles, and SoCal traffic, the sound became more frequent and more severe. And I started to not be able to accelerate quickly from a stop without severe shuddering (I've checked CB and U Joints). At this point I thought I had bought a bad torque converter from the jump and needed to replace it, so I did (this time with a Transtar Recon unit). I was pretty confident in the procedure since I had already done it twice. However, upon reassembly and testing, I ran into the problems that I've listed above.

Thanks in Advance!

 

Can't give much help other than to bump up your post and point you towards a huge thread on the A750F transmission which you may or may not have already found during your swap. More info there than you'll ever be able to comprehend.

https://www.tacomaworld.com/threads...th-pics-for-second-gen-4-liter-trucks.289913/

Maybe the resident expert can help...paging Doctor @gearcruncher ?

 

Sure sounds like the ring gear is rubbing on your inspection cover .

For the codes , did you have the key on when you did the work ?
Try disconnecting the battery , then reconnect battery to see if the codes come back.
The codes should be gone

 

When working, I disconnected the battery. I did all of this in my apartment complex lot, so when I was done for the night, I plugged the battery back in so I could lock the truck and my stuff in it. I did go for a simple battery reset the last time I did it but no luck. I will try it again when I get back (currently traveling).

I really appreciate this guys!

 

Another area of concern is the transmission harness where the transmission harness joins to the internal transmission harness .
That connection is well known for corrosion

 

Hey guys. Just got back from a long bit of travel and opened up the truck to start looking into the issues. I pulled the starter and turned the crank to see if I could see any cracking or signs of wear in the starter hole. The flex plate from what I can see looks good (I understand that sometimes folks have found damage upon removing the transmission from the engine so I won't completely rule that out), and there are no signs of wear on the ring gear, the flex plate bolts, or the starter gear. The bendix on the starter looks to be working as normal too... which likely means that the source of the grinding sound is behind the torque converter if it is coming from a purely mechanical issue

Are there any ideas as to what it may be? Could the electronics issues be linked to the sound?

 

torque converter failure will cause ALL of this. thats what it sounds like to me.

 

and or valve body

 

It's a brand new converter

For additional context, I pre-filled the converter before install and checked to make sure that there was one-way resistance on the stator

 

This is starting to get a little tricky .
When you replaced the converter , a good rule of practice is to verify the converter fits into the rear engine pilot before installation . Sometimes you gotta use emery cloth to remove any paint on the new converter pilot and lube up the converter pilot as well as the pilot hole in the back of the crankshaft .
Sometimes , the old converter pilot breaks off inside the crankshaft . This would have created a massive bind up during installation .
The weak point is the alluminum transmission pump .
Before you installed the converter bolts to the flywheel , that new converter should have spun freely.
Can you confirm the converter spun smoothly ?

Next : did you unplug your electrical connector at the transmission and have a look at the wiring male and female pins ?

It sounds like you have multiple issues with the transmission . If you had all those codes , the transmission would have been starting off in 2nd or possibly 3rd gear .
At this point , further investigation would be needed to diagnose this properly .

If your truck was at my shop , I would be removing the transmission pan for a contamination inspection .

 

Oddly enough I didn't have to fight the transmission very much when I installed it. There was not a lot of friction on the last inch that the trans needed to move to mate the bellhousing to the block. However, I did not check the pilot before I installed it. I did spin the converter behind the flex plate as a sanity check to make sure that things were in properly, and got the expected free spin.

Today, I'll take out the flex plate bolts, to check the spin of the TC again, as well as drain the pan and pull it to check the fluid. I'll report back with what I see.

If it helps, the first time I ran it after startup, the sound went away slowly (after about 2 mins). I put it into gear to see what would happen, and got what felt like no pressure in drive (had to rev to get the truck moving, but RPMs dropped like normal upon the initial shift), and in reverse I got a harsh jerk. To me, my only takeaway from this was that the pump is at least providing pressure.

 

If you had all those codes in memory at the time of start up , I could understand the truck not feeling correct when selecting forward movement .
The computer in your truck sees a big problem and compensates by only allowing third gear . You would have to fix all the codes before trying forward .
https://www.tacomaworld.com/threads/a750f-a750e-p2716-wiring-harness-short-fixed.527281/
The reason it fealt ok in reverse is becuase reverse is all mechanical .
The flywheel noise is another issue altogether .I have my fingers crossed your transmission pump is still good . It does sound like you installed the trans to converter correctly .

 

Status update:
Converter spins freely behind the flex plate. Not much noise.

Filter looks to be lightly 'seasoned'



I looked at the internal harness for damaged wiring. This bend was the only section that looked strange. Nothing looked visibly broken. I have a new harness on hand that I will likely swap in.


I took some more photos but they weren't very good. Either extremely glared or completely dark.

 

A little too much metal in that transmission pan and filter .
Do you know the mileage on the transmission

 

Total mileage on the transmission is about 185k miles

 

Did the internal wire change help?