ZF slippage after fluid change

markrinker

markrinker

New Member
Jul 19, 2011
325
Lake Union - Seattle, WA
Boat Info
2000 410DA
Engines
Caterpillar 3126
3128 385hp with ZF 800 series 1.6 ratio

ATF out was still pink and not stinky, burnt, or carrying any visible particles. After the service, I tested forward/reverse function and verified fluid levels but boat was only operated at low speeds of 7knots or less. About a month passed before taking the boat to bigger water where I attempted to put the boat on plane and was met immediately with clutch slippage on both sides. With some careful throttle application and "coaxing past the troublespot", WOT RPMs could be attained with normal expected speeds, as well as throttling back and maintaining on plane cruise at 2300 RPMs.

However, slippage during acceleration from dead stop to on plane could be repeated at will, on either side, depending on which throttle is advanced ahead of the other.

Called our local ZF transmission repair facility, their CAT/ZF transmission guru seemed less than alarmed with this following fluid service, pointing out that the 385hp version of the 3126, mated to the ZF 800 series are 'running at the edge' of what the clutches can hang on to. He suggested to troubleshoot that I perform the following, in this order:

  1. Verify that both shift cables are properly adjusted for 100% engagement
  2. Verify that filters (not changed at this service) are not restricted - recommended replacement
  3. If slippage continues, remove and replace ATF with 15/40 motor oil
  4. If slippage continues, they would come out and line test the pressures and determine the next course of action

I am not panic'ed, as this certainly seems fluid related, and the fact that it is BOTH sides quite equally seems to support that, but isn't ATF the same viscosity brand to brand?

Chevron MD-3 ATF was used...
 
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I'm no guru, but I know there are different ATFs for different car makes. I would certainly find out what ZF recommends and change to that with the new filters. If you keep using it, you may burn up clutches
 
If you removed and cleaned the strainers, it is possible that the o-ring seal is leaking on the filter cap. The filter assembly is on the suction side of the pressure system so if it sucks air, you will lose pressure on the clutch pack and get some slippage. It isn't that hard to get paint chips on the o-ring when you pull the filter out of the hole, so you might want to check that before getting exotic in the diagnosis, especially since the transmissions pulled normally before the fluid change.
 
The filter caps have two orings. One that is squeezed between the two cap halves and seals to the case of the transmission and the other smaller one that pushes into the filter sealing the filter to the cap. The filter looks symmetrical, but it is not. Only one end of the filter will push on to the cap. If the filters are installed upside down and the cap set on top of the filter and not pushed into the filter you won't get a good seal and this can cause air to get sucked into the transmission which frank points out as a potential problem. The filters only have to be cleaned, not replaced. I put them in a funnel lined with a coffee filter and spray them clean with brake parts cleaner. After I'm done I look at the filter for particulate matter rinsed out of the filter. I press the filter on to the cap and install it as an assembly. One other thing to note is that the fluid level is checked with the dipstick placed into the transmission not screwed in. Hope this helps.

Good luck

Pete
 
Thanks all - from the input here and of the ZF repair shop, I have a good plan. Have looked at a new filter here in our Service Dept and agree that all but the worst case should be easily cleaned and reused.

Unfortunately I'm not sure when I'll get to this project between work, a minor surgery, and holiday travels... Will check back once I have new info.
 
Well I had some time over holidays to get back at this project. Pulled the old filters (which were not changed when the fluid was last fall) and they looked used, but certainly not plugged.

Took them to a local repair shop. The service manager sold me two new filters, I reinstalled them without incident. First thing I noticed at startup when checking for leaks at the cap was the starboard shaft spinning slowly at idle while in neutral. In the past only the port side did this.

However the test run was similar - the slippage was the same. Maybe some slight increase in flow would explain the starboard idle/neutral rotation. My plan is to find a nylon fitting matching the ZF drain plug to a 3/8" nipple, attaching a length of hose to the oil change system and completely re-drain both transmissions. The ATF removal at the change was done with a vacuum tube down into the filler cap.

Question: What spec ATF does the ZF80 call for? Chevron ATF MD-3 says "Recommended for automatic transmissions for which former DEXRON-III fluids are specified (revisions G and earlier). According to www.harbormarine.net/transmission-service the Chevron should have worked...but obviously didn't. I am planning to use Mobil One ATF, based on the information I have.
 
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I am using Castrol Transmax in my ZF HSW 800 V-1 which is the same transmission as the ZF 80 IV. No slippage. The only issue I am having is that the transmission fluid leaks past the filter caps and I can't get it to stop. I am thinking about machining some of the metal away between the caps so it will squeeze out the oring further and make a better seal.

Pete
 
The drain plug on the ZF-80-IV is 1/2" NPT..................

But, you can't remove the plug with the fluid in the transmission without dumping about 2 gal of ATF in the bilge. You will need to vacuum or pump it again thru the filter cavity or dip stick tube. Once you get that much AFT out of the way, you can just put a shallow pan.....tuna fish can?, baking pan? cut down milk jug?...under the gear box and remove the plug and let it gravity drain. There isn't going to be very much remaining.....a cup or a little more....because ZF designed the gear case to allow pumping at it lowest point which is under the filter housing.
 
I read an interesting bit of advise about the ZF transmission. AFTER you install the filter cover (and of course fill with oil) run the engine and put some ATF around the filter cap and make sure it does not get sucked in. If you have a leak there and it sucks air, your transmission will slip. You also might want to check your linkage adjustment and make sure that when you are in gear the shift lever (on the tranny) is ALL the way to the end of its travel, and when in neutral it is centered and in the detent.

Pete
 
fwebster said:
The drain plug on the ZF-80-IV is 1/2" NPT..................

But, you can't remove the plug with the fluid in the transmission without dumping about 2 gal of ATF in the bilge. You will need to vacuum or pump it again thru the filter cavity or dip stick tube. Once you get that much AFT out of the way, you can just put a shallow pan.....tuna fish can?, baking pan? cut down milk jug?...under the gear box and remove the plug and let it gravity drain. There isn't going to be very much remaining.....a cup or a little more....because ZF designed the gear case to allow pumping at it lowest point which is under the filter housing.
Click to expand...

2 gallons??? I've told you million times not to exaggerate, Frank! ;)

...although my lack of the suction tube was what propelled to envision draining with suction from the plug. Maybe I'll run a length of hose from my oil change pump and use a similar flex tube to evacuate through the filter housing?

I like this hybrid approach. If I do swap drain plugs this farm boy moves fast and a fresh oil absorbent pad will catch the rest.
 
peterkvs said:
I read an interesting bit of advise about the ZF transmission. AFTER you install the filter cover (and of course fill with oil) run the engine and put some ATF around the filter cap and make sure it does not get sucked in. If you have a leak there and it sucks air, your transmission will slip. You also might want to check your linkage adjustment and make sure that when you are in gear the shift lever (on the tranny) is ALL the way to the end of its travel, and when in neutral it is centered and in the detent.

Pete
Click to expand...

At idle with the filter cover removed, the fluid backs up slowly to overfill the filter housing. (Don't ask how I learned this.) I can only assume that placing the transmission into gear (which I did not) would cause that level to drop. If I have an assistant with next time, I'll test this.

The new O-rings provided with the filter appear to seal well. I don't think this is a air problem, as only fluid was changed before, the filter caps weren't touched.

Cable travel for shifters is 100%. I intend to have an assistant next time and will do more measurements and center (N) verification.

Thanks for recommending the green Castrol ATF. At 180, it has the highest viscosity index of any brands I've investigated, and the green color will be distinctive to identify any new leaks. (On edit...Mobil Multi-Vehicle ATF claims a 193 viscosity index spec.)
 
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The fluid capacity of your transmissions is 7.4 quarts......so I guess I exaggerated by .6 qts.........Excuse me.......I'm not here to argue, only to help. But, remember this exchange when you can't get the nipple in the transmission and you are mopping up 7.4 qts of ATF out of the engine sump.

IN fact, I've been here and done this before. I have hydraulic hoses in t he transmission sumps to aid in pumping the fluid out:


transdrain.jpg
 
See? Great minds think alike. :grin:

Question: Are there any other seals (...preferably that are servicable with the ZFs still in the boat) that could allow air into the system?
 
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Mark - Look at the cover of the manual you referenced and look at the cover of my manual (lower left corner):

ZF-80 IV.jpg

Don't you have ZF0 80 IVs​?
 
This is the tag...so either they are grossly under filled, or only about 2/3 of the old fluid was removed using the suction tube method.

I'll go back to the boat tomorrow and get a new reading on the dipstick, WITHOUT screwing it back in.


Thanks for all the input...
 

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Part of your problem may be that you are referencing the wrong transmission manual.

Your photo shows that you have Hurth HSW-800-V, not ZF-80-IV transmissions. ZF bought Hurth and redesigned the HSW-800 into the ZF-80-IV, fixing some known issues, then redesigned it again into the ZF-85-IV. One major difference is the transmission fill plug and dipstick design was changed. The HSW-800 has an expandable rubber plug that is fully seated in order to check the fluid level. The ZF-80-IV has a threaded plug that isn't seated but only contacts the threads for checking the fluid level.

Also the whole question of fluid volume on these transmissions is confusing because the external lines and oil cooler hold fluid. If you follow the manual procedure, i.e. run the engine before changing the fluid, your lines are full and you will never get all the fluid out, nor will it take 7+quarts to fill the transmission.
 
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