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Toyota A750F - Weak Reverse and Now O/D Acting Like Neutral


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GTOGuy
New User

Feb 22, 2016, 8:37 AM

Post #1 of 4 (7653 views)
post icon Toyota A750F - Weak Reverse and Now O/D Acting Like Neutral Sign In

Hello Guys,

My vehicle is a 2004 Toyota 4Runner 4.7 V8 with the 5spd A750F transmission with 4WD at 155k. My symptoms:

1. A 'weak reverse'(no noises or bangs) revs and moves barely;

2. No OD, recently acting as 'neutral' if manually selected;

3. No braking in 3rd and slight braking in 4th.

Vehicle drives normally 1st thru 4th without any noises, shudders or slippage - Shifts really well, actually. At speed, transmission seems to shift into OD as RPM's drop accordingly...but acceleration is not possible as it acts as it is in neutral. Shift back out of OD and the vehicle will drive fine.

There never was a 'bang' associated with change to reverse. Fluid level checked and re-checked numerous times at Toyota's recommended temperature using overflow level drain.

Toyota WS fluid seems to show normal to deep red dirtiness. Solenoids were removed and bench-tested and function within parameters of Toyota transmission manual. Pan strainer cleaned recently changed out four quarts to new WS fluid. Transmission was not power flushed. Running Toyota's WS fluid always.

Wiring harness grounds were cleaned which improved shifting. Transmission harness connector not corroded. Reverse unchanged if transmission harness unplugged. Vehicle never went into limp-mode.

No CEL or constant engine codes aside from what seems to be Toyota generic of mismatch of input/output sensors when testing OD. Vehicle will drive without generating codes for forward 1st-4th. Codes cleared without incident.


No unusual particles found on pan magnets. Black dirt was clinging to magnets and wiped off bottom of pan. To me not a huge collection of particles. No dirt found in solenoid screens when bench tested. A new Toyota SLT linear solenoid installed without a change in performance.

I am hoping to have transmission fixed rather than replaced. Any checks I can do??



Thank You in Advance,

Walt P


gsferraro
Veteran

Feb 22, 2016, 11:09 AM

Post #2 of 4 (7642 views)
Re: Toyota A750F - Weak Reverse and Now O/D Acting Like Neutral Sign In

There is a common clutch to 5th and reverse gears in this unit, The B1 clutch is on only in 5th and reverse. If you wanted to air check the clutch, you would have to drop the valvebody and mid way down you will see 3 seals in the case, the middle one is for B1 clutch(or B1 Brake). Also, there may be a port for a gauge, if there is one it would be in front of the line pressure tap(may be labled B1, but not sure if its there). Gary


GTOGuy
New User

Feb 23, 2016, 7:49 AM

Post #3 of 4 (7619 views)
Re: Toyota A750F - Weak Reverse and Now O/D Acting Like Neutral Sign In

Hello Gary and Thank You for your reply.
I and glad to hear a reply from you describing knowledge of the A750E/F. I have visited three transmission shops and I have been told these units do not show up for repairs. Turning techs loose on an unknown transmission to them makes me hesitant. I value your insight.
According to the images below, I am seeing the C3 Clutch is on during both R and 5th (OD). Is that where you think the issue can be? Worn clutch steels?? Or...valve body pressure leaks? I'd like to point direction to a decent repair shop.
I am in NJ outside of NYC by 30mins...Where's your shop Gary? I'd love to give you some business. : )






gsferraro
Veteran

Feb 23, 2016, 8:30 AM

Post #4 of 4 (7612 views)
Re: Toyota A750F - Weak Reverse and Now O/D Acting Like Neutral Sign In

 Hello,
I did not mention the c3 clutch, because that is on also in 3rd, and you had posted that shifting up 1-4 is good, but yes you are correct, that clutch is on. Very suprised no codes are present.






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