Hey guys, new to this forum. Been at the dieselstop for awhile now, but decided to branch out. Anyway, changed tranny fluid on my ZF. I know a lot of people are overfilling tranny which seems to help it operate better. Was wondering how much over the fill line people are filling it. Thanks, Nick.

 

That's the first I've heard of overfilling it. I don't know how you'd accomplish that. Full is at the bottom of the fill plug.

 

You don't want to overfill it. It'll just come out the overflow when you're pulling hard. Oil expands quite a bit when it's hot.

 

You overfill it by taking off the shifter boot and dumping the ATF straight into tranny. You don't overfill much, but enough which helps tranny run cooler in 5th.
I wasn't aware there was an overflow on the ZFs.

 

Are you talking about the overdrive gear of a ZF-5 or the 1:1 gear of a ZF-6?

Wouldn't you be better off adding an external cooler? That way you would get the superior cooling and the extra capacity without the need to overservice it.

I guess I just don't understand how more fluid in the case is going to keep it cooler...it'll take longer to heat up, but eventually will be just as hot.

 

Well I'm not real familiar with Ford's transmission concerning overflow. But there has to be some sort of hole somewhere to equilize the pressures inside with the ambient pressure outside. That's all I am referring to. Get it full enough and hot enough and something is bound to come out.

And Cookie's right about getting a cooler. More oil won't run any cooler, just take a little longer to heat up.

 

I've got the ZF5. It's in a 96 PSD. I've got synchros on the way out in the thing. supposedly shifting will improve a little if you overfill some. I have a cheap cooler (www.fastcoolers.com) but will probably go with an external pump and plate cooler when the time comes. At the moment I don't want to spend $400 on a cooling setup.

 

Does it feel like every syncro is going out? Or is it isolated to one gear? Reason I am asking is if it seems like every syncro is going out, I would be more suspicious of a clutch that won't disengage.

 

on the zf's its more than likely that you have a clutch on the way out if it is grinding shift to shift, worse in the lower gears, especially 1-2 no matter how you are driving it, my bucket truck has 300k on it and it was doing all that and put a new luk clutch in it and it shifts like new. if you overfill theese trannys they just leak out of the shift boot. i pulled my pto plate and put a cooler in mine, the pto was making the thing hotter than hell sitting still and having to run it. got my cooler gear for about 250 having a hard time finding the site again though. ill give you an up date when i find it. also check the little stupid plastic shift bushing on that down by the clutch petal, that thing goes and it wont fully disingage either. theres a guy on ebay that sells a replacement for that for $40 built a little hiem joint one that should last the rest of the truck and it made pedal push a little easier. if you clutch has been getting harder to push i bet its just getting time for a clutch, rebuilding theese trannys gets expensive quick


jake

 

Jake, my clutch isn't very old. I'm running a Luk SMFW and Luk clutch. I've checked the plastic bushing on the clutch pedal. I don't think that is the problem. It is only 3rd gear that is grinding, and all the others are just as bad as they are normally. I have a cooler on my tranny (www.fastcoolers.com). It does nothing as far as I can tell, although I didn't install the temp guage until I installed the cooler, so I have nothing to go on. The only real way to cool these trannys is to put on an external pump, mount it to the frame and plumb in a plate cooler like the auto trannys have. Pump is $300+. I'm just going to throw in an extra 1/2 quart above fill line and see how it goes. Nick.

 

Not sure about the ZF-5, but the ZF-6 has an internal pump in the belly of the tranny housing that is driven off the countershaft. I assumed the five speed was the same.

Does it pop out of any gears or is just grinding in third?

 

There is no pump in the ZF5. All the thing does is sling around the fluid that is in there. Hence the overfill, which slings a bit more around. I will eventually go to the external pump, which is the only way to get real movement out of the fluid. It does not pop out of any gears, but it grinds going into third if I'm not careful. I really have to wait for the rpms to die after putting in the clutch or it will grind. I'm talking about a 2-3 second at least wait before shifting.

 

Yep, broken syncro.