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When does the ZF tranny oil need to be changed?

nuck

Member
Joined
Apr 3, 2004
Messages
16
Location
Edmonton, Canada
Corvette
2002 Procharged vert
I don't recall ever doing it in the old 4 speed cars but the technology has changed obviously. In a sealed unit does age of the fluid matter, or should you be looking strictly at mileage? My 96 has only 24k on it so I wouldn't be assuming the oil is degraded but what do you guys think?
 

Hib Halverson

Technical Writer for Internet & Print Media
Joined
Jan 10, 2001
Messages
13,453
Location
CenCoast CA
Corvette
71 04 12 19
I change the lube in my ZFs every 3 yrs or 36,000 miles.

I use Red Line Light Shockproof gear lubricant in them.
 

nuck

Member
Joined
Apr 3, 2004
Messages
16
Location
Edmonton, Canada
Corvette
2002 Procharged vert
It looks like ZF says every 30,000 miles so you are right on there. It also looks like the recommended product is actually an engine oil rather than a gear oil:confused

TRANSMISSION OIL (status) - Vascular flow of oil through the porous Phosphorus-bronze (Pb) material of each synchronizer is essential for effective British Thermal Unit (BTU) heat exchange occurrence. Frequent transmission oil changes will ensure lower Pb particle levels suspended in the oil. The ZF S6-40 6-speed transmission is lubricated by engine type oil. Manufacturer recommendations specify the use of GM P/N 1052931 (5w-30) or BMW P/N 07510009420 (10w-60) oil.
Approximate oil capacity of the ZF S6-40 is 2.2 quarts.
FYI - the BMW 10w-60 oil is fully-synthetic and is used in the BMW M5 engine. "From Bill Boudreau's site"
 

LT4man

Well-known member
Joined
Jun 25, 2003
Messages
2,214
Location
Chicago
Corvette
96 Collectors Edition LT4
I change my trans fluid every two years. Simple operation. Doesn't take too much time.

Last time I changed it, I used the BMW oil. What a difference! I had been running synthetic oil in the trans since 1996. One of the first things I did upon delivery. Going to the BMW oil made the trans even quieter and it shifts even more smoothly than before.

SAVE THE :w
 
Joined
Sep 16, 2003
Messages
525
Location
Newark, OH
Corvette
2003 50th Anniversary Convertible
I change the lube in my ZFs every 3 yrs or 36,000 miles.

I use Red Line Light Shockproof gear lubricant in them.


Is the gear lubricant better than the BMW oil? Mine is due for a change and I am just curious.

Thanks!

Jim
 
B

Black Bart

Guest
Is the gear lubricant better than the BMW oil?

NO it is not recommended in the ZF

Go to www. ZFdoc.com and read why this tranny should not have gear oil.
The oil needed is because of the bronze cone synchronizers.
If you want to experiment a rebuild is only around $ 3500.00
Here is a copy and paste from the ZF Doctor web site.
(A.) Jim, the C4 Corvette ZF S6-40 6-speed transmission uses engine oil for lubrication. I was told by Jeff Henning, Warranty Administrator of ZF Industries North America, that Engineering of ZF Industries in Germany determined that the BMW imported Castrol (RS superceded by TWS) 10W-60 oil was the recommended alternative to the (GM P/N 1052931) factory-fill oil for use in the ZF S6-40 transmission. In effort to verify ZF Industries alternative lubricant recommendation, we ran our own test series on the BMW imported Castrol TWS 10W-60 oil. Independent testing of the transmission oil samples was sub-contracted out to CTC Analytical Services. The test series went as follows:
<1> Spectrographic analysis indicated that it is has full synthetic composition.
<2> After 2 hours of operation, approximately 100 miles, oil sample analysis tests indicated that the viscosity rating was reduced from 60 down to a 43 level. No need to worry, this is a normal occurrence for this heavier type of oil. I attribute this to microscopic-level lubricant-strand trimming through operational loading where all of the oil contents has been passed through gear pressure-loading regions at least a few times.
<3> At 200 miles, the viscosity level stabilized at a 42 level viscosity since the 100 mile oil analysis test results.
<4> At 5000 miles, the oil analysis test results indicated a 40 level viscosity.
The test-transmission was completely disassembled and checked for wear. There were no signs of carbon film like experienced with the factory-fill oil. The phosphor-bronze lined synchronizers had no glazing and experienced an average mass loss of approximately 4% based on reserve-wear-range mass equivalency between 0.062"(new) and 0.048"(spent)
gap wear/mass measurements.
<5> At 10,000 miles, the oil analysis test results indicated a 39 level viscosity.
<6> At 12,500 miles, the oil analysis test results indicated a 37 level viscosity.
<7> At 15,000 miles, the oil analysis test results indicated a 34 level viscosity.
The test-transmission was again completely disassembled and checked for wear. There were no signs of carbon film like experienced with the factory-fill 30 oil. The phosphor-bronze lined synchronizers had no glazing and experienced an average mass loss of approximately 17% based on reserve-wear-range mass equivalency between 0.062"(new) and 0.048"(spent) gap wear/mass measurements.
<8> At 15,000 miles the oil had enough phosphor-bronze particles suspended
in it that deposits began building up inside of the synchronizer sliding
sleeves from the normal centrifuge-like rotational occurrence.
In Conclusion, until someone invents a copper magnet, we recommend that the ZF S6-40 6-speed transmission oil be changed at 10,000 - 12,000 mile intervals so as to minimize the amount of deposits of the suspended spent synchronizer material from collecting in critical component contact surface areas.
 

arp35

Member
Joined
May 23, 2007
Messages
5
Location
Alabama
Corvette
1996 Polo Green LT4
I am in the process of changing mine. I am going to use the Penzoil Syncromesh fluid which is the same as the GM equivalent but half the price. I purchased a fluid transfer kit from autozone and once I drain the old stuff will use the kit to pump in the 2.2 qts of fresh. Here was my problem...it took 3 days of penetrating spray and hammering/swearing to get the fill plug out. Make sure you can get the fill plug out before you drain the fluid using the drain plug otherwise you will be screwed. I had to grind down the 17 mm hex bolt adapter in order to get a decent grip on the plug as well as use a hammer against the side of the exhaust to hold the hex bolt in the plug to get a good grip while turning. This may be best done on a lift but I did it in my garage on jack stands. Finally the bolt turned (after 3 days) and then I tackled the drain bolt. It loosened with less effort. Needless to say I ordered 2 new bolts $8 bucks online x's 2, and will replace the old ones. I will also put some anti sieze on the threads. I do not think the fluid was ever changed so 11 years of corrosion had basically locked the bolt in place. I was about to take it to the pro's because I was too timid to use the heat/cold process for removing stuck bolts. Anyway, I just thought I would give you my experience on how a simple job can turn into a nightmare. Fortunately, it has turned out ok and no trip to the dealer. Alan
 

Florida Guy

Well-known member
Joined
Oct 16, 2003
Messages
166
Location
Florida
Corvette
'96 Torch Red LT4
I copied the following 2 Q&A from the ZF web site.

Q: What type of oil do I need to use in my ZF S6-40 Corvette transmission?
A: ZF only recommends the following lubricant for S6-40 transmissions. The GM oil (available from GM with part number 1052931) and the Castrol Synthetic Formula RS 10W60 (available from BMW with part number 0751009420).

Q: What is the recommended service interval for my ZF S6-40 Corvette transmission?
A: The lubricant should be changed every 30,000 miles.
 
B

Black Bart

Guest
I copied the following 2 Q&A from the ZF web site.

Q: What type of oil do I need to use in my ZF S6-40 Corvette transmission?
A: ZF only recommends the following lubricant for S6-40 transmissions. The GM oil (available from GM with part number 1052931) and the Castrol Synthetic Formula RS 10W60 (available from BMW with part number 0751009420).

Q: What is the recommended service interval for my ZF S6-40 Corvette transmission?
A: The lubricant should be changed every 30,000 miles

.
If you look at the test that I posted above you will see that the oil is shearing down from the pressure and he recommends a 15000 change interval.
I change mine every 6000 miles. A couple of Qt. of oil is a lot cheaper than a
$ 3500.00 rebuild.
I'm also putting a lot more power to mine than most people do so it would shear down faster.
 

2fast

Member
Joined
Sep 22, 2006
Messages
19
Location
TX
Corvette
96 CE LT4 vert. plus 2015 C7 Z51
If you look at the test that I posted above you will see that the oil is shearing down from the pressure and he recommends a 15000 change interval.
I change mine every 6000 miles. A couple of Qt. of oil is a lot cheaper than a
$ 3500.00 rebuild.
I'm also putting a lot more power to mine than most people do so it would shear down faster.

The manual for my 96' CE LT4 6 speed, says the transmission fluid does not need to be changed, so it has no reccomended change schedule. Where is all of this change info coming from?
 
B

Black Bart

Guest
The manual for my 96' CE LT4 6 speed, says the transmission fluid does not need to be changed, so it has no reccomended change schedule. Where is all of this change info coming from?
If that is what your manual says the only expiation I would have is GM wants you to think that their cars are so good that they don't need maintained.
If you want to risk damage to a $ 3500.00 transmission rebuild to save buying two quarts of oil be my quest.
I changed mine at 6000 miles
 

Florida Guy

Well-known member
Joined
Oct 16, 2003
Messages
166
Location
Florida
Corvette
'96 Torch Red LT4
The manual for my 96' CE LT4 6 speed, says the transmission fluid does not need to be changed, so it has no reccomended change schedule. Where is all of this change info coming from?

As you can see, my info came from the Trans manufacturer. Just changed mine at 47K miles and used the BMW synthetic. I would never have thought it would be so much smooooother. I'll change mine again in 15K miles.
 

lefoy84

Member
Joined
Jun 29, 2003
Messages
7
Location
Heart of Dixie
Corvette
96 CE LT4 Roadster
The new part # for the GM oil is 12345349. I used it and am happy with it. I recommend 15,000 mile interval.
 
R

Red Rocket

Guest
5W50 Castrol full synthetic

I called my local BMW dealer to price this 10w60 tranny/motor oil. They want $17 per litre. So, while I was at Walmart tonight I noticed a Castrol 5w50 full synthetic on sale for $6.86 a litre. I picked up 3 and plan to replace the oil this weekend. My LT4 has 56,000 miles and the fluid has never been changed. Since the original fill was a 5w30 I'm thinking this 5w50 should be just fine. Any comments or concerns on this are appreciated. Also any suggestions for rearend fluids?
 

LT4man

Well-known member
Joined
Jun 25, 2003
Messages
2,214
Location
Chicago
Corvette
96 Collectors Edition LT4
I called my local BMW dealer to price this 10w60 tranny/motor oil. They want $17 per litre. So, while I was at Walmart tonight I noticed a Castrol 5w50 full synthetic on sale for $6.86 a litre. I picked up 3 and plan to replace the oil this weekend. My LT4 has 56,000 miles and the fluid has never been changed. Since the original fill was a 5w30 I'm thinking this 5w50 should be just fine. Any comments or concerns on this are appreciated. Also any suggestions for rearend fluids?

According to Gordon Killebrew and Bill Boudreau (zfdoc) the answer is no. The GM oil and the BMW oil have certain friction modifiers that are necessary for the metals which are used in the transmission.

SAVE THE :w
 
B

Black Bart

Guest
I called my local BMW dealer to price this 10w60 tranny/motor oil. They want $17 per litre. So, while I was at Walmart tonight I noticed a Castrol 5w50 full synthetic on sale for $6.86 a litre. I picked up 3 and plan to replace the oil this weekend. My LT4 has 56,000 miles and the fluid has never been changed. Since the original fill was a 5w30 I'm thinking this 5w50 should be just fine. Any comments or concerns on this are appreciated. Also any suggestions for rearend fluids
?
Since you ask for comments Here is mine
NO WAY IN HELL I WOULD USE IT.

I found the Castrol at a BMW dealer for 12 bucks shop around.
Look at it this way you will drive 25000 miles before draining
.
Depending on how much you drive your car but you may get several years per change so you are going to risk a $3500.00 rebuild to save 3 dollars per year not even enough to buy a gallon of gas.

I use Mobil-1 full synthetic in my rear end it don't need the additive for the clutch pack it is already in their and can be bought reasonable at Auto Zone

Lubricates is the life blood of your vehicle I just never could understand why people will risk it to try to save just a couple bucks
 
R

Red Rocket

Guest
Thanks for the replies. I hear you guys and fully agree about the cost and the difference in the product. You're definately right ....who would risk a $3500 rebuild for just a few bucks. I didn't know the BMW product contained other additives. That being the case I'll opt for the better product. The 5W50 will be going back and I'll be using the 10w60.
 

96CERon

Active member
Joined
Sep 15, 2002
Messages
44
Location
Phoenix
Corvette
CE 1996
I called my local BMW dealer to price this 10w60 tranny/motor oil. They want $17 per litre. So, while I was at Walmart tonight I noticed a Castrol 5w50 full synthetic on sale for $6.86 a litre. I picked up 3 and plan to replace the oil this weekend. My LT4 has 56,000 miles and the fluid has never been changed. Since the original fill was a 5w30 I'm thinking this 5w50 should be just fine. Any comments or concerns on this are appreciated. Also any suggestions for rearend fluids?


Stick to the ZF recomendations of GM or BMW oil.

I went with Redline synthetic with an extra bottle of limited slip additive for the rear axle. You have to suck it out or drill a drain hole.
 

Edmond

Well-known member
Joined
Aug 1, 2001
Messages
5,218
Location
Louisiana
Corvette
2003 Z06
Hey guys,

Just thought you'd like to see a cool little fluid extractor that I built:

vacuum.jpg


It's just a 2.5 gallon gas tank with a fitting drilled in it for a 1/4" hose. Where the spout is, you put a shop vac slightly in so whatever fluid you want extracted will get sucked in through the 1/4" hose but not into the shop vac.

You could drill a fitting for a 3/8" as well if you'd like.

Cost was about $10 total. It's got great capacity and easy to dispense for disposal.

I'm going to change the trans fluid in my GP and this is what I'm going to use. I still have to take the pan out to get to the filter but at least there will be very minimal spilling of the old fluid.
 
Joined
Jul 28, 2004
Messages
799
Location
Phoenix, AZ
Corvette
Blk/Blk '96 LT4 Coupe
Nice job Edmond...should work well. :beer
 

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