Transmission- 5 Speed automatic write up with pics for second gen 4 liter trucks

So the zip kit wont help or will it help? My transmission does not have issues upshifting, it has issues downshifing.

 

Are you even reading what I just explained ?
A downshift issue is totally different than an upshift problem

 

Had a question for you and forgive me if you have already covered it. I looked through all the info you posted about transmission issue but was a little overwhelmed by the amount to find a possibile solution to my situation (although im sure you probably did mention a fix). l drive an 2008 Tacoma Prerunner TRD sport Double Cab with Automatic Trans and the transmission seems to intermittingly slip when going from 3rd to 4th gear. Doesn't always happen but it seems to happen more when its cold or colder weather. Have had it in the dealership off and on during the 2 yrs ive owned it and have heard various reasons but none of which have explained the slip. Fluid has been topped off to appropriate level by dealership but my confidence in the people Ive dealt with at the Toyota dealership is non-existent. If you maybe provide some possible solutions or point me in the right direction it would be greatly appreciated.

 

Link to subscribe

 

Where the SLU screw located? I cannot find an illustration anywhere for the A750 tranny. Thanks

 

The screw adjustment is located in the center of the SLU solenoid . The SLU solenoid is mounted to the side of the valve body. Are you absolutely positive you have a converter shudder ? Any recent wiring done to your truck ? Lift kit or aftermarket tires ? Has it been diagnosed correctly ?

 

Absolutely. Will not shudder in 4th. 7 inch lift with 35's for over 2 years. No wiring done. Thx

 

The slu should be #6 on the diagram?

 

Is it this with the Alan head screw?

 

http://www.valvebodypros.com/a750.html

http://www.sonnax.com/parts/1774

 

Does anyone know how to prevent the A750F from downshifting from 4th to 3rd? I'm trying to dyno some engine modifications and the dyno requires a full acceleration in 4th gear. So far I can only get a reading from about 4,000 to 5,500 RPM due to the downshift.

 

I don't have an answer for you... but what are you running? Stock will redline 4th gear at about 136mph (assuming the speed limiter is disabled and the engine can actually get the truck to that speed).

 

When I had a baseline dyno run on my brand new Tacoma, I found out that they had no way of running the test through the entire RPM range with an automatic.
Here is the Power and Torque graph vs speed, you'll notice the limiter cuts in at 87 mph in 4th.



I've had the TRD supercharger installed and will have it dyno'd again, if I can keep it in 4th gear without it automatically downshifting, we could get a much better picture of the hp and torque.

Eventually, I'll install an exhaust and maybe a few other performance odds and ends to see how they help as well.

 

What tires and gears are you running? I can do 80 mph in 3rd gear with 33's and 4.88's.

With stock gears 3.73's and 31's, you can do about 95 mph in 3rd gear.

4th gear gets you over the 115 mph speed limiter in both cases


EDIT: Looks like 28's and 3.73's will cause 3rd gear to redline at about 87 mph.

 

It's a 2015 Tacoma Double Cab Long Bed V6 5 Speed Auto with TRD Sport and Tow Package (now with Super Charger). The tires are Bridgestone 265/65R17's, according to manufacturer's site, the diameter is 30.5 inches. The differential ratio should be 3.73, according to the Toyota brochure. And the A750F transmission ratios are as follows:



Using this information, the 87 mph doesn't make sense for 4th gear, does it.

RPM x 60 / gear ratio / diff ratio x tire circumference in inches * 63360



I'm thinking now that the dyno guy didn't run the test correctly. That was money well spent! ugh.

Thanks BradyT88. I appreciate you bringing that to my attention.

 

I did a lot of research into gear ratios and such when I was planning on regearing. A quicker way to find the numbers is this calculator but I had done most of it by hand before I found the calculator. The A750F is listed in the drop down menu. Although it looks like you used a calculator for your info as well unless you made your own spread sheet.

http://www.grimmjeeper.com/gears.html

 

I have a question OP. 07 Pre runner running 37s. Got a check engine light and would shudder really bad in OD. I did a drain and fill and it helped for a few hundred miles, I was on stock gears so now I changed to 4.88 gears and it helped a lot. Almost no shudder ever. There are some times when it shudders just when cruising in OD and I still have the CEL. So I did the lube guard and drove all day without shudders, I cleared the CEL and it came back on in a few miles, but no shudders. Any idea why I'm still getting the CEL?
Thanks for this post its awesome by the way.

 

Wait? You cleared the CEL and never checked what code it was throwing?

 

No, I checked the code. I dont remember the exact code, right this second, but its the torque converter code.

 

Sub'd