ZF Gearshift Bias

[SteveB]

My gearshift works well; however the side to side springloaded bias for fourth and fifth is quite strong. The gate is naturaly set to second and third. Spring resistance toward first and reverse is a little heavy but I've become used to it.

Question is; can the bias spring tension on the selector shaft be adjusted by changing the spring rate or some other way. I have tried a longer gear shift lever to improve the leverage that improved the feel.

Any one with ZF experience have any suggestions?

Thanks

Steve

 

[O-RING]

Steve,

You can change the springs on the cross shaft. Depending on what spring you have there may be a softer one available. Is your gearbox a ZF or RBT what is the model number off the type plate? 1031-???-???

Oliver

 

[SteveB]

Hi Oliver

The box is a ZF 5DS-25 -2
Stuckl nr 1031 002 131
Getriebe Nr 011973

Thanks for your help

Regards

Steve

 

[O-RING]

Hi Steve,
Your gearbox if it were in the original configuration should have one of the lightest springs ZF offered going into the 4<SUP>th</SUP> 5<SUP>th</SUP> gate. The gearbox was originally built for a Giocattolo so it is possible that a heavier spring was installed when it was converted to your application. You can inspect or replace the spring after removing the shift box.
Best regards
Oliver

 

[SteveB]

Oliver

Thanks for the info. Again I am amazed by the depth of knowlege in the members of this forum.
Which bits of the numbers identify the box to a car I had previously never heard of?
Is there a spring rate for the various options that I can use to identify what I have installed and then identify a lighter item, but from where?

Again thanks for your help with this

Steve

 

[O-RING]

Steve,
The 002 131 tells me what gearbox you have. The light spring has 11 coils of 1.4mm diameter wire. If you need one it can be purchased from RBT Transmissions. They advertise on the forum.
Best regards,
Oliver

 

[SteveB]

Oliver

Thanks for the detail, I'll contact RBT if I need a new spring.

In fact it may be another cause. I have disconnected the linkage from the gearbox end and removed the cover plate to access the mechanism.
What I thought was resistance from the selector shaft spring now appears to feel like hydraulic resistance.

My gearbox is inverted so the selector shaft is in the gear oil, I wonder if the blind end of the shaft bearing at the opposite side of the gearbox from the selector box,fills with oil that then has to be displaced to allow the selector shaft to move across the gate. This may be the resistance I feel as I shift from third across the gate to fourth.

Is it possible to create a relief hole/path/duct ? Has this been a problem with anyone else?

Steve

 

[MICK.(southerngt)]

Hi steve had this problem with my zf box i drilled the end of the housing and fitted a braided hose and returned it back into the box above the oil level.this cured the problem as it was pressurising across the gate the faster you moved the gearchange the harder it became. Regards mick.

 

[SteveB]

Mick

Thanks for the info.

I removed the blind end housing for the selector shaft, there is a groove in the bore to allow oil to escape so it was a bit of a surprise that there was a hydraulic effect.
On closer check the spring retaining washer actually seats up against the face where the oil needs to escape from and is under spring loading. This sets up resistance to the oil flow.

I used the same relief method and created a bypass from the outer end back to the gearbox case.

I also found the spring loaded button in the hex plug that fits in the bearing cover was putting a lot of resistance to the shaft movement, I have shimmed this back to ease the pressure.

These changes have made the shift a lot better.

Steve