I recently began to experience a delay in downshifting when pulling to a stop. If I used the rolling stop method, it would shift hard upon acceleration. Given the cat's high miles, I thought I should at least change the trans fluid and filter.

After the new fluid and filter swap, the downshift issue was worse once everything warmed up. Cold it was fine. Accelerating enough to cause a downshift would make it slip about half the time. If I used the manual shift (leaving it in 4th) it seemed to be better and driving like a granny always worked.

After reading online, I decided to try some Lucas no-slip additive. This did not improve things so far, it might even be worse. Has only thrown a transmission fault once (just today) and there are no codes my reader picks up.

Any other suggestions? Time for a new transmission? Sacrifice a Kia to appease the car gods?

 

It sounds to me like there is a crack in the valve body or a badly scored or worn valve. Not necessarily a transmission replacement but inspection of the valve body.

 

Thanks RJ237, somewhat comforting to think valve body vs. total rebuild or replace.

Guess I'll be looking for a ZF transmission shop very soon.

 

Many foreign car specialists have experience with the ZF since it has been used in BMW, Audi and others.

 

Just a quick update. It finally threw a fault code & check engine light. Code is P0732. "Wrong gear ratio". It got stuck in 4th. Pulled over, turned off engine and it shifted again when I restarted.

I have called about 6 places today and apparently no one rebuilds transmissions anymore. Only one place even discussed doing any diagnostics. Everyone just wants to swap out the transmission.

Prices ranged from $2300 (used box) to $4500 (remanufactured). Going to try again tomorrow. Surely someone does diagnostics and/or rebuilds. Hate to pay that much if all it needs is a new valve body or electrical work (unlikely I know).

If anyone in the DFW area knows a good transmission shop that is familiar with the ZF 5HP24, please let me know.