2010 PreRunner Trans Issue - Slams into gear

I’ve been lurking around for a while and have found lots of great info on this site. Recently I’ve been stumped by a transmission issue that started about two weeks ago and could use some help and input on.


I drove to lunch ~20 miles, no problems, an hour later while heading home I began experiencing problems with the truck slamming into gear after decelerating and accelerating again. When coming to a stop it would ‘jerk’ again feeling as if I was rear-ended. Got home, no check engine light, no codes on the scanner.


I read through almost every post of the transmission thread ( https://www.tacomaworld.com/threads...th-pics-for-second-gen-4-liter-trucks.289913/ ). After coming across the write-up about “Truck slams into gear”. ( http://bluegrasstoday.com/wp-content/uploads/2012/07/a750e_shudder.pdf ) I was fairly convinced the SLT solenoid was the culprit. I checked the fluid level with engine running and AT fluid at temp and got what I would consider a steady drip from the overflow so assumed the level was correct.


I went ahead with the first two mechanical test here: https://www.purefjcruiser.com/docs/...sion/Automatic Transmission System/017003.pdf. The stall speed checked out fine. The R range lag time was close to 1.5 seconds, but the D range lag was closer to 3.5 seconds.


Still convinced it was the SLT solenoid, I ordered a new solenoid, (Rostra 52-0590), filter, and 6 qts of fluid. Dropped the pan following Hook78’s write up and replaced the solenoid. A little over 5.5 qts came out, put just shy of 6 qts back in. Cycled through all of the gears several times, got the fluid up to temp then drained maybe 0.25 qt from the overflow with the engine running and AT Fluid at temp.


The fluid that came out didn’t look terrible or smell burnt, magnets were pretty clean, bottom of the pan was a little gummy almost like a light grease consistency. Nothing visually looked out of sorts.


Still having the same issues, 3.5-4 second lag time in D range and truck slams into gear after decelerating and while coming to a stop. Occasionally it will shift hard from 1 to 2 but it’s not consistent. At this point I’m not sure what could be causing the issue or how to diagnose it, maybe failing pump or valve body leakage?

Hoping @gearcruncher or other experts or someone who’s had a similar issue can weigh in.

Truck is a 2010 Tacoma Prerunner, A750E transmission, 162k miles. I’ve had it for last 2 years and put ~25k miles on it and had no transmission issues up until this point. Not sure of the history before I had it.

 

Its a computer controlled transmission .
Next step would be to scan the truck and post up the codes .

 

Unfortunately, it’s not throwing any codes.

or maybe the Bosch OBD 1100 I have won’t read the codes???

 

Ujoints? Just spitballin here.

 

Are you close to auto zone ? they scan for free .
Might be worth it to double check .
Some transmission codes are hidden .
I guess the next step would be a pressure gauge to verify pressure when you get those big slams into gear .
Part of the bluegrass write up is measuring the pressures before installing a new SLT .
There was a member last week with your identical issue . He also replaced the SLT and still had issues .
He ended up replacing his rear springs and driveshaft . You may want to have a quick peek at those . ( axle wrap )
You could have sticky valves inside the valve body which would give the same symptoms as a bad SLT solenoid .

When this happens , a valve body kit needs to be installed

https://www.sonnax.com/units/396-a750e

 

I pass an auto zone picking up kids in the afternoon, I’ll swing in tomorrow afternoon and get them to scan it to double check.

I’ll also look over the rest of the driveline and rear springs in the daylight tomorrow.

I’ll see about getting what I need to check the pressures as well, saw that in the bluegrass write up but figured I’d roll the dice with buying the solenoid vs buying a pressure gauge and fittings to connect it, you win some you lose some…

 

Went by autozone yesterday and got them to scan my truck, no codes.

Sick kids kept me from doing much else, I will try to inspect the driveline and spring over next few days or this weekend and get a pressure gauge connected.

Is a $15 bottle of lubeguard worth trying to see if it helps?

 

Ok @gearcruncher I connected a gauge to check the hydraulic pressure at idle in reverse and drive.

In the video below you can see when shifting from neutral to drive the pressure ‘jumps’ to ~80-85psi for about 2 seconds before dropping to 55psi and engaging. In reverse by it immediately jumps to ~75-80 psi and engages. Then I shift from N to D again with a similar result.

https://youtube.com/shorts/BlTYpv4tqm8?si=5zDX84BBVVZGetLK

Not sure what to think of this. Seems the pressures are in the correct range according the link below but the D range shift time lag is over 3 seconds and the pressure spike before dropping. Also I had the gauge connected to the test port as shown in this link

https://www.purefjcruiser.com/docs/...sion/Automatic Transmission System/017003.pdf

I also triple checked the fluid level with the engine running and AT Temp and got a steady drip from the overflow.

 

I agree that your pressures dont seem to be too bad .
It would be great if you could reproduce the pressure when the transmission does its downshift bang thing . I know its difficult to test drive and watch the gauge at the same time . If you could possibly drive the truck and have someone else watch the gauge to record the pressures .
I beleive you need to reproduce the pressure while driving
I dont like the fact that your pressure jumps to 85 psi before the transmission goes into drive range first gear . The transmission should not be developing that much pressure for forward range .
That being said , we can pretty much rule out your universal joints and rear springs .
I do beleive you have crossleaks or worn valving in the valve body providing your Rostra SLT solenoid is functioning correctly .
Awesome job with your diagnostics up to this point . Most people give up before this .

Will Lubegaurd work in this situation ? That is a tough call to make . Lubeguard is very well known for getting transmission valves unstuck .
The stuff is that good !!
You could throw a bottle at the trans for 20 bucks and see what it does but I cant guarantee it will fix you up .

The reason is , currently , we dont know if you have a sticky valve or a wore out valve .
If the valving is sticky , chances are Lubeguard will free it up
If the valve is worn out , Lubeguard is a waste of money because Lubeguard cant put that missing aluminum back into the valve bore

 

I bit of good news (I think), after doing the pressure check above last Saturday, when I got in the truck Monday the problem seemed to have fixed itself, no more long shift time lag and no slamming into gear. I’ve driven it the last few days and have not been able to recreate the problem.

That leads me to think it was a valve sticking that has since freed up, but I’m a very much a rookie to auto transmissions so other opinions are welcomed.

I plan to pick up a bottle of lubeguard and more fluid to do another drain and refill this weekend which should put me around 500 miles since dropping the pan and re-filling.

I had already ordered a couple of fittings and longer hose to be able to connect the gauge with the hose routed in a manner to be able to drive the truck while also monitoring the pressure so I still plan to do that whenever the parts arrive.

 

I'm also having this same issue after I had the transmission fluid changed. I'm interested to see where you land on this.

 

What procedure did you use to change the transmission fluid ?

 

Pay someone else to do it. I could call and ask them. Will different procedures possibly raise this issue?

 

This may be a little unpopular.. But I changed my pop's trans fluid for his automatic 05 prerunner. Used toyota's new oem fluid "world standard". Suddenly it started slipping in gear.
I went back and the dude behind the counter told me, quietly, that the newer fluid has too many detergents.

I switched over to redline, can't recall if it was d4 or d6. Problem was resolved - no more slips trying to pass a car on the freeway, or while downshifting for a stoplight. Throttle would cut out then, yeah, just slam super hard - it was pretty sketchy.
Needless to say, my good deed cost me a vote of confidence But changing the brand of trans fluid worked. You don't have to use redline, either. I just knew of it from my bike, which has a wet clutch. Guys recommended redline (engine oil) because it didn't cause clutch slip.

Edit: I know what I'm pitching here is Eastern medicine. I've got a tried solution, and I've repeated it on other vehicles, recommended it to folks on the Fitfreak Honda Fit forum who reported back with success (none using my recommended brand).. I just need someone educated to come along and prove it!

 

Absolutely .
The way the transmission is serviced is imperative to the proper function of the trans .
Many mistakes can be made during the service procedure causing your issue on a transmission with miles on the odometer

 

Do you have a resource for the right way to do it? Also, what do you think of the impact of fluid formulation stated above?

 

This is a good read .
The proper and only way the transmission should be serviced .
If it was done any other way , it was performed incorrectly and you are asking for trouble
https://www.tacomaworld.com/threads...e-2nd-gen-transmission-pan-and-filter.726329/

 

If the service was not performed as described in the thread, then will reperforming the service correctly solve any issues? Or is there still potential for issues to persist?

 

Accumulator issues maybe.

 

If you managed to service your transmission different from the link provided , consider yourself one of the lucky members here at Tacoma World and carry on until your next trans service is due

In most cases , when the transmission pan is dirty , the new fluid introduced lifts the junk off the pan and spreads that junk into the valve body within a couple days . Its very likely to have issues when the transmission has never been serviced along with higher mileage but can also happen with brand new trucks off the dealership parking lot
That being said , if you find everything is working well with your transmission , chances are , that the bottom of your pan was very clean .