Transmission valvebody casting number/transmission issues

Good Evening!

new owner of a 2015 Tacoma v6 with Off Road package 5 speed auto 93k miles.

Having a annoying issue when I’m stopped at a light for more then a few seconds I feel the transmission kinda thump and seems like it falls out gear and then when I take off there will be a hesitation then the pops into gear and at times chirp the tires. This is very inconsistent, but incredibly annoying.

Read through gearcrushers thread on 5 speeds auto trans…Excellent read!

here’s what I have done so far;

Dropped the trans pan and clean out and clean off magnets. Fluid pretty dark

replaced SLT Solenoid according to an article I found in gearcrushers thread this can cause this issue, just not enough wear to cause a code.

drain and fill transmission using WS fluid using proper fill method. Not a flush and fill

new sparkplugs
Clean MAF
Clean Throttle body
New air filter
Grease driveline

issues seems slightly improved still there

i was thinking of purchasing a used valvebody and adding a TransGo shift kit. This way I can take my time rebuild the VB without taking the truck off the road.

But I’m unsure of the valve-body casting number? See a few on EBay but I’m unsure which.

Also, since I am unsure of the previous maintenance.. I thought about doing another drain and fill adding Lubegard Platinum and driving for a few weeks.

Thoughts and ideas, suggestions welcome!!!

 

If it only happens at idle, I would be thinking about problems associated with low pressure. A weak pump is a possibility as is a failing o-ring on the 1st gear actuator. Had this problem on a bmw. Rebuilt the trans and the #1 o-ring was toast. With foot on the brake and car stopped and fallen out of gear, increase rpms and see if it pops back in.

 

Thanks for the reply back, can you give me a part number or an image of this actuator?

Beside this issue the truck seems to shift correctly

 

The actuators are the hydraulic unit that engage each different gear in the gear complex. All the gears are spinning at all times and the one with the actuator engaged is the one that is connected to the output shaft. This is where your solenoid is sending the pressure to actually engage a gear. You only get to these parts with a full tear down.

The actuators never fail, but the oring inside them often does. Hopefully, you find an easier fix. It could be the pressurized fluid is losing pressure somewhere else like a solenoid or sticking spool valve in the valve body. My theory is that the leakage or blockage, wherever it is, is minor and only shows itself at low pressure. Hydraulic pump is driven at crankshaft speed and the lower the RPM, the lower the pressure. Pressure is regulated like your oil pressure with a bleed relief, but once volume drops below the bleed off level, pressure drops with lower RPM. So, it is possible that only at 800 RPM is your pressure too low to hold the 1st gear engaged. All other shifting is taking place above 800, so no issues seen. Just a theory, not a diagnosis.

Don't know, but guessing the trans has a pressure sensor inside reporting to the trans module. WIth the right reader, you should be able to see that pressure and can then compare to eng specs on the trans to be sure the pump is producing adequate pressure at idle. That would point to the actuator of the valving that regulates #1 pressure. If there is not sensor, there is likely a tap point to install a gauge to get a pressure reading. On some transmissions, the pump can be replaced without a teardown. Never done and aisian trans, except the Honda, which was really a manual trans with hyd actuated gear dogs. Most AT's are planetary gear setups.

 

Did you try to reset the ECU so the shift points have to reprogram? Aside from the "falling out of gear" part, the "thunk feeling at a stop" is a normal phenomenon with these trucks.

Just hoping you didn't go too far into thinking this is a true transmission issue since the A750 is a rock solid trans.

 

@gearcruncher

Thoughts, since he's referencing one of your writeups?

 

I think the op perfomed everything I would have asked him do if he contacted me .
As mentioned above , the next step would be a Toyota Techstream scanner for checking parameters when he feels the transmission drop into neutral . 99 % of the time , replacing the SLT solenoid fixes the issue . At least for the guys I have helped over the years , the SLT solenoid did the trick .
This is providing the SLT solenoid is being charged with the correct pressure from the pressure regulator .
The op is not complaining of neck breaking engagement as identified by the link below .
The pressure checks are listed in the illustration
Here is the document http://bluegrasstoday.com/wp-content/uploads/2012/07/a750e_shudder.pdf

This being said , the spool valves behind the SLT solenoid would also cause the same symptom as a faulty slt solenoid .
The problem is actually viewing a pressure drop in line pressure when the transmission falls into nuetral .
Can you confirm the torque converter is unlocking when slowing down ? Sometimes they are slow to release
The OP would need a pressure gauge connected to view line pressure as mentioned above .

His valve body is up to date considering its a 2015 model . Those valve bodies were the last ones used and then Toyota Tacomas moved up to the AC60 6 speed automatic .
As I understand , newer 4 runners still use the 5 speed automatic , so there may be a possibility of upgrading to a newer valve body .


What would I do ?

Connect a pressure gauge and monitor line pressure for the next couple days .
Need a pressure gauge thats good for zero to 450 psi and 10 feet of hydraulic hose so you can run the gauge into the cab

I dont beleive Trans-go has a fix for this issue in their shift kits

I know Sonnax sells reconditioning kits for the valve body , but they are pricey $$$$$$
Before spending the cash , it wouldnt hurt to do a few more diagnostics .

I would hate to have the OP spend a bunch of cash and labor only to find out the problem is caused by something else .
https://www.sonnax.com/parts/3477-zip-kit

Identification guide
https://www.sonnax.com/tech_resources/224-toyota-a750e-a761e-identification-guide

 

First off thanks for all the replies!

So I did another drain and fill today and added the 15 oz of Lubegard Platinum. As a precaution to protect the transmission until I come up with a fix.

I don’t know if I am dreaming this up in my head, but it seems improved.

The take off from a stop didn’t produce as much delay then such an abrupt shift. Maybe a little bit but not as severe. But this does not happen all the time.

I’ve read alot of threads describing this situation. Is this more a characteristic of this transmission?

I have no check engine lights, and I have a scanner but it only sees the engine ecu no trans module. If there was an electronic issue would it throw a cel?

Is there a scanner available for troubleshooting trans issues that’s not big time bucks?

thanks everyone and I will keep everyone in the loop.

 

Disconnect battery and let it sit for a few mins and then reconnect to reset ECU.

 

I would like him to triple check the fluid level with the engine running in park

 

When I did this last drain and fill little over 3 quarts came out. I filled with 3.5 quarts lost a little bit during the Trans Temp mode drain.

So is the Sonnax look at as recommended maintenance? It matter if…but when?

I would really like to find a used VB to rebuild offline. But the casting codes are hard to figure out.

 

Transmission fitment by year:
2005-2007,
2008-2011,
2012+

There is an overhaul manual at this link https://www.tacomaworld.com/threads...th-pics-for-second-gen-4-liter-trucks.289913/

it should show you casting numbers

 

So everything seems improved, but I feel it a little bit at times

I see owners doing the Sonnax Zipkit and Transgo kit? Would these solve this issue? Can these be used together? look at the manual for each kit it seems to address different areas of the VB.

Thoughts?

 

Not a good idea to mix kits .

If I had my choice , Sonnax zip kit is the way to go .
You are going into the valve body blindfolded mind you .
Unless you plan to test pressures before you purchase the kit ?

 

You are correct, not good troubleshooting.
I see the kit on BO at Summit and that's the cheapest vendor as well. The kit will not be in stock till 11/4, so my thought was better to have it and not need it and then need it and having to wait again.

I can troubleshoot till arrival and summit has good return policy.

bad idea?

 

Strange to see Summit selling Sonnax products . In most cases , you can only purchase the Sonnax kit through Sonnax or a transmission shop although I have seen some vendors on Amazon selling Sonnax at a mark up.
Trans-go kits are moreless designed for guys with superchargers and turbos .

Because you are going in to fix a possible pressure issue , the Sonnax zip kit is a far better choice .
They are more expensive than the Trans-go , however , the Sonnax kit also covers more known problem areas inside the valve body .
You can tailor your shift points to function the same as a Trans-go shift kit .

To answer your question . Not a bad idea at all if Summit takes things back with ease .
Lubeguard does wonders for sticky valves inside the valve body . Lubeguard is very good
Got my fingers crossed with a little more driving , Chances are the lubeguard will clean up the problem .
Its unusual for a truck with your mileage to show signs of valve body wear unless your pan was filled with metal and clutch debris .
Was this the first time the transmission was serviced ?
Do you know any history about how the truck was maintained ?

 

I have the carfax maintenance records but it does not show what was performed. It just says recommend maintenance performed.

All the routine maintenance was done at a Toyota dealership.

Soon as I purchased the truck I changed all the fluids and performed all the recommended maintenance. Truck has 93k miles

I would say debris on the magnets was not over the top. The fluid was darker than I was used too.

 

Good to know the pan was clean .

Type your vin number in here and see whats been done to your truck at the dealership before you owned it
https://www.toyota.com/owners/

 

No record of transmission issues.

That’s some great info!

 

Just read an interesting TSB about the slip joint

I am going to try greasing the splines

https://static.nhtsa.gov/odi/tsbs/2012/SB-10061275-2273.pdf