Why the ZF fluid changes?
Thread Starter
Instructor
Joined: Aug 2006
Posts: 140
Likes: 0
From: St. Louis MO
Why the ZF fluid changes?
Can somebody explain to me why the trans fluid in the ZF's needs to be changed so often? I've got a 94 LT1 with the ZF 6-speed, and I've seen several posts about changing the trans fluid every year. What is going on inside the gearbox that would make this necessary? I can understand it in an automatic, since it's basically a hydraulic system, but the ZF (or any other manual) just has a bunch of gears spinning around, right? No combustion or anything...
By the way, I'm just talking about a street driver... no racing.
Thanks for any insight.
By the way, I'm just talking about a street driver... no racing.
Thanks for any insight.
Last edited by fuzzydawg; Nov 20, 2006 at 01:50 PM.
Race Director
Joined: Dec 2002
Posts: 13,348
Likes: 233
From: SCMR Rat Pack'r Charter Member..Great Bend KS
Originally Posted by fuzzydawg
Can somebody explain to me why the trans fluid in the ZF's needs to be changed so often? I've got a 94 LT1 with the ZF 6-speed, and I've seen several posts about changing the trans fluid every year. What is going on inside the gearbox that would make this necessary? I can understand it in an automatic, since it's basically a hydraulic system, but the ZF (or any other manual) just has a bunch of gears spinning around, right? No combustion or anything...Thanks for any insight.
Replacing the lubricant is not expensive. Your choice on whether to do it or not.....
Larry
code5coupe
Melting Slicks
Joined: Dec 2004
Posts: 3,284
Likes: 51
From: Jacksonville, FL
St. Jude Donor '08 thru '26
Figure it as cheap insurance against having a parts failure due to lube oil failure?
I went to zfdoc's & read the test that they did and decided that 40% remaining lubricity was as far as I would trust an oil to go down to and still be effective....that's my excuse.
Besides when you are under the car doing the fuel filter every yr, the trans plugs are right there along with the oil pan drain plug, etc, etc,....ya know the old "while we're here" thing? Seems like as good as time as any to me.
Tom
I went to zfdoc's & read the test that they did and decided that 40% remaining lubricity was as far as I would trust an oil to go down to and still be effective....that's my excuse.
Besides when you are under the car doing the fuel filter every yr, the trans plugs are right there along with the oil pan drain plug, etc, etc,....ya know the old "while we're here" thing? Seems like as good as time as any to me.
Tom
Safety Car
Joined: Apr 2003
Posts: 3,793
Likes: 9
From: VA
Originally Posted by fuzzydawg
Can somebody explain to me why the trans fluid in the ZF's needs to be changed so often? I've got a 94 LT1 with the ZF 6-speed, and I've seen several posts about changing the trans fluid every year. What is going on inside the gearbox that would make this necessary? I can understand it in an automatic, since it's basically a hydraulic system, but the ZF (or any other manual) just has a bunch of gears spinning around, right? No combustion or anything...
By the way, I'm just talking about a street driver... no racing.
Thanks for any insight.
By the way, I'm just talking about a street driver... no racing.
Thanks for any insight.
In a manual gearbox in a street car, I will usually replace around 30k intervals, which is being overprotective. You should be able to go 60k easily.
Check fluid condition once a year, sure. But replace it regardless of condition, no.
Team Owner
Joined: Aug 2000
Posts: 40,156
Likes: 45
From: San Pedro CA
www.zfdoc.com
surf that site... there is a FAQ there with a breakdown of his testing and why he recommends 12k mile intervals.
surf that site... there is a FAQ there with a breakdown of his testing and why he recommends 12k mile intervals.
Team Owner
Joined: May 2002
Posts: 24,337
Likes: 25
From: San Diego , CA Double Yellow DirtBags 1985..Z51..6-speed
The 10w60 lube breaks down really fast from shearing, and gets contaminated quickly from copper.
If it's not flushed, ZFdoc says the the copper dust from the syncrhos get where it doesn't belong and blocks the lube from doing its job.
It doesn't surprise me that the 10-60 shears down so quick, but why is synchro wear such a problem that it turns the fluid into a copper milkshake?
If it's not flushed, ZFdoc says the the copper dust from the syncrhos get where it doesn't belong and blocks the lube from doing its job.
It doesn't surprise me that the 10-60 shears down so quick, but why is synchro wear such a problem that it turns the fluid into a copper milkshake?
Drifting
Joined: Oct 2005
Posts: 1,915
Likes: 48
From: Angier nc
i bought mine with 89k on the clock.i was told it was changed every 15k miles.i have and will continue to do so.it shifts perfectly and i drive aggressively.it is about to hit 100k so proper maintenance is essential.
what is the old saying,an ounce of prevention is worth a pound of cure.......
what is the old saying,an ounce of prevention is worth a pound of cure.......
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Melting Slicks
Joined: Dec 2004
Posts: 3,284
Likes: 51
From: Jacksonville, FL
St. Jude Donor '08 thru '26
Originally Posted by CentralCoaster
The 10w60 lube breaks down really fast from shearing, and gets contaminated quickly from copper.
If it's not flushed, ZFdoc says the the copper dust from the syncrhos get where it doesn't belong and blocks the lube from doing its job.
It doesn't surprise me that the 10-60 shears down so quick, but why is synchro wear such a problem that it turns the fluid into a copper milkshake?
If it's not flushed, ZFdoc says the the copper dust from the syncrhos get where it doesn't belong and blocks the lube from doing its job.
It doesn't surprise me that the 10-60 shears down so quick, but why is synchro wear such a problem that it turns the fluid into a copper milkshake?
I'd like to know all of those answers!My only thought is the clutch hydraulic system is so filled with design compromises that it doesn't stay at a great level of performance to prevent the blocker rings and the dogs on the syncros from getting abused????
Team Owner
Joined: Jun 2001
Posts: 26,196
Likes: 0
From: Orlando FL
St. Jude Donor '08-'09
130K miles, never been changed. Still going strong (except 3rd gear syncro going)
I only found out about the need to change this a few weeks ago while surfing around on the forum. It might explain my tranny getting very hot while in stop and go traffic too.
I have plans to change it this weekend, thanks to all the info I found on the forums here
I only found out about the need to change this a few weeks ago while surfing around on the forum. It might explain my tranny getting very hot while in stop and go traffic too.
I have plans to change it this weekend, thanks to all the info I found on the forums here
