Automatic Gear Box Trouble - Late Shift to 4th Gear

[Pawel66]

A kind request for help from a Club Member here:

1. Automatic transmission shifts late on the 4th gear and on the 4th gear only.
2. It shifts normally across lower gears.
3. No slipping.
4. They adjusted modulator pressure by the book
5. They checked the pressures on particular gears: on the 4th gear the pressure is too low, other gears are ok.
6. They swapped the valve body - same late 4th gear shifting

What can be causing the low pressure on 4th gear?

I found only 2 threads related to late shifting, 1 thread on late 3 to 4 shifting, but inconclusive (governor topic or not governor topic).

I already told them to check ignition timing and vacuum profile - I am not sure if wrong timing can cause late shifting just to 4th gear, but they can check it anyway.

Please kindly advise.

[MartinK]

Hei. Does the car shift often between 4th and 3rd gear, is there a kind if jiggling between the gears? Maybe there is a problem with the regulator assembly (broken coil spring or problem with the oil supply of the regulator unit).

[Pawel66]

Thank you for your kind attention!

I will ask. It was not part of info I received.

[BobH]

Hello Pawel, i'm sure you've read through the tech manual

I know very little about transmission, in fact you could write what i know on the gear knob!

Have a read through, it mentions both vacuum modulator pressure or the double acting solenoid as possible culprits

https://www.sl113.org/wiki/Automatic/Start

Hopefully one of the gearbox experts will chime in when they read your post

[zak]

Pawel, at what rpms does your trans shift into 4 th gear at normal acceleration ? - then hard acceleration ?
Also, if you shift manually thru the gears does the trans act the same going into 4th ?
Does the kick down work normally ?

jz

[Pawel66]

Hello Pawel, i'm sure you've read through the tech manual

I know very little about transmission, in fact you could write what i know on the gear knob!

Have a read through, it mentions both vacuum modulator pressure or the double acting solenoid as possible culprits

https://www.sl113.org/wiki/Automatic/Start

Hopefully one of the gearbox experts will chime in when they read your post

Thank you!

The tranny is worked on people who know what they are doing - they just got stuck and cannot figure out why modulator pressure is within specs across gears except the 4th one, where it is too low. They went through the basics....

They asked me to ask here for help.

[Pawel66]

Pawel, at what rpms does your trans shift into 4 th gear at normal acceleration ? - then hard acceleration ?
Also, if you shift manually thru the gears does the trans act the same going into 4th ?
Does the kick down work normally ?

jz

zak, thank you, I will ask.

[Pawel66]

Hei. Does the car shift often between 4th and 3rd gear, is there a kind if jiggling between the gears? Maybe there is a problem with the regulator assembly (broken coil spring or problem with the oil supply of the regulator unit).

Once it shifts, it holds. No changes back and forth.

[Pawel66]

Pawel, at what rpms does your trans shift into 4 th gear at normal acceleration ? - then hard acceleration ?
Also, if you shift manually thru the gears does the trans act the same going into 4th ?
Does the kick down work normally ?

jz

zak, here is the answer I received:

"The transmission shifts to 4th gear at approximately 45-55 mph. and
4000 rpm. , and it should be about 3000 rpm. for economical and correct
city driving. With a slight release of the gas, continue driving around the
city at a speed of 30-35 miles/hour. - the 4th gear should be maintained at
all times, while the gearbox gently shifts to the 3rd gear. To get the
transmission back into fourth gear, you need to accelerate to about 45-50
mph. and reach 4000 rpm again. Such driving around the city is very
unfavorable for the gearbox, engine and fuel consumption. The engine has
good torque and works properly in all ranges. The Workshop Manual lists
only one problem similar to this fault: "Engine races in 3rd and 4th
gear" and the cause is "Clutch K1 inoperative. 1. Mechanical
destruction, 2. Insufficient or no operating pressure (sleeve 27 is open) .
The K1 clutch was replaced with another one, the "sleeve 27"
works properly. Kick down works selectively, it is rather non-existent.
Changing the lever manually from 3rd to 4th gear does not work."

[MartinK]

Hi, If the centrifugal regulator does not work properly, the transmission shifts too late, too. If the piston stucks or the coil spring is broken or the oil guidance rivet left its correct position, it could disturb the gear change. If all other maintenance did not succeed, it is an option to check the regulator.

Picture WA0017 shows the oil pipe pressed into the shaft by the regulator´s coil spring.

You can see on the pictures that the oil pipe is slipped into the shaft and because of that the pumped oil volume is too low and soes not supply enough oil. the picture WA0009 shows the correct position of the oil pipe.

Martin