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A750f Transmission 4th to 5th

bi1965

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Dec 1, 2018
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australia
Hello Landcruiser guys, I have owned my 100 series 1HDFTE 2003 model for 12 years, I noticed lately that the change between 4th and 5th is a little bumpy. The Automatic oil is spotless and it has only done 170000km has anyone else had any experience with this.
 
Just to check the cheapest solution first: Make sure you are checking the ATF level with the engine running.
Also, if this is a 4-speed, a synthetic fluid performs better than a mineral. How long since the fluid was changed?
 
I have done the level hot, I also measure what comes out before I refill.
 
Yes, the level is best checked hot (normal operating temp), but also with the engine running, in neutral or park.
 
Thanks, but I have triple checked oil in the transmission, I had a transmission place look at it and he told me to keep driving it but its not the same shift as before.
 
Hello Landcruiser guys, I have owned my 100 series 1HDFTE 2003 model for 12 years, I noticed lately that the change between 4th and 5th is a little bumpy. The Automatic oil is spotless and it has only done 170000km has anyone else had any experience with this.

When you say "bumpy" you mean it slips and engines is over revs? I have an ideea or two regarding different issues with A750.
 
Don't like the adverts?  Click here to remove them
When you say "bumpy" you mean it slips and engines is over revs? I have an ideea or two regarding different issues with A750.
Hello, I gave it a service again this week (The oil is like new) and the auto pan had no metal in it. when its changing into top gears say 4th to 5th it is bumping in instead of a smooth change (The gearbox has always been smooth in all gears) I tested the resistances on the solenoids they all seemed fine, any help would be good as I'm not selling this car and its a little annoying knowing it never did it before.
Regards Brett.
 
Don't forget the gear change solenoid has a hydraulic side of it .
The coils may well be checking out resistance wise but if the little spool inside the solenoid is sticking that could well cause your problem .

Is 5-4 OK or is that also bad

Difficult to diagnose if it's 4th hanging onto a bit of pressure or 5th being lazy .
Best way to see what is going on would be if the entire coil and valve is the same for all speeds then swap 4 and 5 for 2 and 3 ....that should move the problem to that gear change if it is the solenoid valves causing a problem .
You could then swap again to finally diagnose which 1 valve is faulty .

Used to do a lot of work on big Full Power Shift Ag boxes and a faulty PWM valve could make a real harsh change . We used fairly tech stuff to look at clutch pack pressures and also milliamps applied to the PWM from the trans controller to produce a graph of all the gear changes , sometimes the dumping off of
pressure in a clutch pack was slow so both packs were momentarily trying to drive again produced a harsh change or a bump and not a smooth change, again if a pack is slow to take up pressure that will cause a bump or bad upshift .
We could also calibrate clutch packs to compensate for wear .

No idea what level of diagnostics is possible on a Toyota Auto box or if it even has pressure test ports that can be accessed with the box still in the vehicle and driveable ..... but a couple of gauges would soon show whats happening at that shift point .....have fun .

Edited to add ...... When you resistance checked the solenoid coils were they at working temp or cold ?
Were they all very close to each other or was one different from the rest although technically still within spec ?
 
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Hello, I gave it a service again this week (The oil is like new) and the auto pan had no metal in it. when its changing into top gears say 4th to 5th it is bumping in instead of a smooth change (The gearbox has always been smooth in all gears) I tested the resistances on the solenoids they all seemed fine, any help would be good as I'm not selling this car and its a little annoying knowing it never did it before.
Regards Brett.

Hi Brett
What oil are you using, I,ve only used the WS oil with no issues
Cheers
 
I am currently looking at changing my Manual transmission to a A750F auto and was looking into common failures with tis box.
One of the issues sounds like you guys described and has to do with the Clutch that assists in engaging 4th to 5th Gear as apparently it's one of the smaller ones and can fail - from the description the only long term fix is to have the box rebuilt.
I know this is an old thread so interested to know if there was any updates or has the issue been resolved by the mentioned fixes?
 
The A750F is rock solid. As long a it is treated nicely, the first thing to need replacement are the solenoids, or rather just one or two of them.

Changing from manual to auto includes also the ECU, and in the case of the A750F it is a combined ECU for engine and atm, which works really well. Iirc, there are also some differences with signalling to the instruments.
 
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