rithsleeper

Has anyone put a temp gauge on a zf6 trans while pushing it on a track for about 20-30 min? I run amsoil syncromesh so I'm not too worried and never even thought about it, but I had a coolant hose burn through off the oil filter and while I was fixing it (about 4 hours after last session), it was still screaming hot to where I couldn't touch the fins on the bottom.

Amsoil states temp range from -40 to 300º but for how long I'm not sure...

My shifting gets hard from 4 to 5 later in the day.

mgarfias

http://www.zfdoc.com/S6-40ExtOilCool.htm

rithsleeper

What is the cost of something like that system? Is there a pump? I see the two fans and heat exchanger. Why are there two return lines? Looks like I could rig this system up using a ps heat exchanger and would more than meet my needs since I'm not in 24hrs of le mans.... any costom setups like that someone has done?

froggy47

Call Bill B. He's been doing zf forever & nice guy.

ScaryFast

I wouldn't worry about it. I have been racing a ZF6 (NASA ST2) without coolers for 15 years and only had my first one fail with about 200k miles on it last season. And I believe that issue was caused by the clutch, not temps. The handful of others I know that still run C4's also do not use coolers.

I use the BMW Castrol oil, FWIW.

My issues in the C4 have always been trying to keep the engine cool.

RedLS1GTO

Yup. 100%.

The C4 has it's share of heat related issues when you put them on a track, but in my experience the ZF is not 1 of them.

C66 Racing

Everybody I race with, myself included, all have tranny coolers for this reason. Actually installing a diff cooler this weekend for the same concerns. All C5s and C6s, but the heat buildup will be common to all track day cars.

The fluid doesn't really have a line at which below is okay and above is not. The real problem is that fluids lose viscosity as they heat up. At 300F, a typical tranny fluid's viscosity will be ~70% lower than it is at 212F. Ouch.

I have a purpose built cooler system on mine (put together by Phoenix Performance when my car was prepped for the SCCA). The kits made by companies like DRM and LGM are pretty good. One line runs from the drain plug to the pump which is normally mounted inside the front cover of the rear wheel well, just over the brake duct. Line runs from there to the cooler (mine is in the nose), then back to the tranny fill plug.

RedLS1GTO

I'm sure it has happened at some point to somebody, but I have never seen a single C4 (with a ZF) have an issue that could even remotely be traced back to inadequate transmission cooling.

You want to go race endurance races or build a big dollar car... sure. Go for it. He said he is running 20-30 minute sessions. For that application there are a whole lot of better places to spend that money on a C4.

C66 Racing

Understand he is running 20-30 minute sessions. In my first DE with my 02 Z06 I got a high tranny temp warning... in only 20-30 minute sessions. Surprised to hear the C4 doesn't have similar issues.

rithsleeper

Thanks guys I agree there are other things to address. Water temps are perfect but oil is different story. Moving to a 7qt pan before next track day might help some... running 270º after a session. I was going to get a bigger oil cooler to help so was wondering if I needed to kill two birds with one stone.

How often do you guys change your trans oil if not using a cooler in a zf6? And just out of curiosity, at what temp does that hot trans warning light flick on on a c5?

RedLS1GTO

There are all sorts of issues that pop up on the C4 when you start beating it up on a track, but the ZF is 1 thing that they got about as close to bulletproof as you can get on a street car.

The D44 ain't too shabby either.

ScaryFast

I probably change trans fluid once a year. sometimes less.

270 is nothing for synthetic oil. I'd be happier with 260 but if you're only seeing 270 then you're far from the danger zone on engine oil.

C66 Racing

I disagree in principle. Synthetic oil, though having a better viscosity index than mineral oil, still looses a lot of viscosity from 212F to 260-270F. The oil companies don't release viscosity at 260-270F so you have to infer what it is. They do release viscosity at 212F and 300F. A typical viscosity of a 30 grade oil at 212F is 10-11 cSt, and at 300F, it drops to 3-3.5 cSt. 260-270F itself isn't going to hurt the oil, but the viscosity loss may hurt your bearings. My own personal thumb rule is that around 260ish I'd go from a 30 grade to a 40 grade and at around 280ish I'd go from a 40 grade to a 50 grade. In my car (C5 Z06 with Ron Davis radiator and external oil cooler), I run AMSOIL's racing 10w30 and my oil temp is usually 245-255F, right at the top of where I feel comfortable with a 30 grade. Above that and I feel the viscosity loss leads to loss of fluid film strength which in turn puts highly stressed parts of the engine like the bearings at risk.

For rithsleeper, the C5/C5 Z06 manual tranny temp warning comes on at about 274F.