4EAT does not engage 4th gear
 

We have a new friend. His first act of SVXness was to get the car fully roadworthy again (I believe it had brake issues and had been standing for quite a few years). Since our Road Being (directly translated hehe) has made a slight error in registration, the VIN does not resolve well and details of the year or trans type is unknown.

What is known is that the car was sold with a transmission issue and that after changin fluids, this issue has persisted. He took the car to a specialist shop for autotransmissions but they could not connect to the TCU. He has tried the self diagnostics and no code is thrown. Since he's new to the car, I'm not 100% certain if he did a transmission diagnostics or engine diagnostics, we'll try to sort that out tomorrow. The specialists drove the car a lot and concluded that the car simply does not even try to engage forth gear.

He seems fairly intimate with cars and mechanics and since he hasn't said anything about sounds, I assume there are no sounds. 1-3 works just fine. I remember reading about something similar on the forum but a good 30 minutes of search did not reveal anything like this.

Any theories or pointers as to where he should go looking?

Re: 4EAT does not engage 4th gear
 

Check the fluid level, brake band could need adjusted or is shot?, check for metal shavings in pan, possibly TC problem?

Re: 4EAT does not engage 4th gear
 

Is this another Norway car Jetboy?

;):D

What I am going to say will be bad news financially, but as he bought the car with the transmission fault, he may be expecting that it will cost money to fix it properly.

I suspect the reason the car is not engaging with 4 is a sticking valve or a servo problem, and the gearbox may need to come out and be refurbished.

When I got my first SVX, a '91 JDM car, I drove it for nearly two years with only gears 1-3 working. [:eek: I am not suggesting your friend keeps driving the car with only three gears, he may not be as lucky as me and the car would strand him somewhere] I got the gearbox re-built and new clutches put in, it remained perfect from then until I sold it years later.

The ATSG troubleshooting chart suggest the following for no shift 3-4 on the 4EAT, in order of frequency:

On-car checks:

3) Faulty control unit [TCU]
23) Valve sticking
16) Faulty ATF temperature sensor

Unit check [aka gearbox out]:

47) [Brake] Band and servo slippage

I am labouring the obvious because your first language is not English, but the on-car checks can be done without taking the gearbox from the car. As follows:

Faulty TCU: simplest plan is stick in a TCU from a known good car; if the problem is solved [and assuming the wiring loom is not damaged] then you know what you need is a good TCU and don't need to strip and rebuild the box.

Valve sticking: the reason this can be checked on the car is you can drop the transmission sump and remove the cassette with the valves and fix the relevant sticking valve. Re-install the cassette, fill up with fresh oil and away you go, assuming a sticking valve was your problem.

Faulty ATF temperature sensor: This one is obvious; if the sensor is faulty and the TCU is only registering a temperature that is incorrect and too low, then the TCU will not allow 4 range to be selected. The objective of this temperature control is to allow the oil in the gearbox to reach the correct higher temperatures through maintaining the higher revs of the lower range gears. If the TCU is not getting the correct expected higher temperature registered by the [faulty] sensor, then the TCU will not allow 4 to be activated and also will not allow lock-up to happen.

It would be very wise to thoroughly investigate these three possible faults before taking the gearbox out for the fourth suggestion.

And speaking of that investigation is your friend sure that the "transmission specialists" you are using know enough about the 4EAT to fix this problem?

The last suspected failure with the gearbox removed: [unit check in ATSG speak]

Band and servo slippage: Personally I would suspect the servo in this case because when the band is loose you also get problems with 2 range, they are both on the same band [ranges 2 and 4], and you do not report fault with 2 range.

When and if you have the gearbox [transmission] out of the car the guys will not be repairing one servo or one band or one clutch. Once the box is out it is usual to rebuild all wear and tear parts and check the operation of all valves etc. That's what makes it so expensive, but is the correct procedure.

This makes it all the more important to check the other faults out thoroughly while the gearbox is still on the car; if you manage to determine it is one of the three suggested faults above, you will save yourself a lot of money.

So make sure your transmission guys know what they are doing. :rolleyes:

Sorry for the long post [guys round here prefer 2-line responses ;)] Best of luck with it.

Joe :)

Re: 4EAT does not engage 4th gear
 

Do you know if the transmission has worked ok after any major work performed on it? Or is this a condition which appeared after someone touched it?

I know someone who :rolleyes: assembled the valve body and, by accident, flipped one of the steel thingies against which the accumulator springs rest the wrong way around.... and this resulted in no fourth gear :-).

This someone had to take the valve body down again to put it together correctly. Thank god for the lift and the drain barrel....

Just what happened to me.... I tried to find a photo, but no luck.

/T

Re: 4EAT does not engage 4th gear
 

Thanks to both of you, long time no see Tapani and yes Joe, I think this is one of the seven. The owner took a photo of the small plaque in the engine room and I could just make out a 'Y' in the type position (trans code). Looking back to the import rules of the early 90s the original owner had nothing to win by importing the car themselves. These two factors strongly add up to this being an original NDM.

I'll pass on your answers as to provide him some clues in his quest. He has been very grateful so far for any assistance I have offered and I'm certain he be no less happy for this. As for the specialist, their only activity is autotransmissions. They are at least 6 employees with a converted barn as shop. They offer a 2 year warranty on their work and is an authorized ZF service shop.

Do they know 4EAT by heart? Not too likely since they didn't have a proper diagnostics system.

The oil they flushed was btw proper.