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Old 05-03-2007, 09:18 PM   #1
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Synthetic Transmission Fluid

Synthetic Transmission Fluid.


We have a 2004 GMC Yukon Denali (permanent AWD) with 9000 miles on it. Approximately 90% of it is used for towing our 25” Safari. Last year the transmission gauge ran a temperature reading between 185-190 degrees. On our first trip out this year, it was running at 200 degrees.

I called our local GMC (fairly large dealer) and inquired about replacing the tyranny fluid to all synthetic. The shop foreman was vehemently against it as he said it will not help the temp range, possibly void the warranty (we have extended warranty) etc. He, however informed me that water vapors do get absorbed by the fluid and after a period of time (regardless of mileage) the efficiency decreases. They only use a so called GMC (OEM) approved transmission fluid and are willing to replace the fluid (I guess they pump it out) for $130.00 complete.

My questions:

1) Are the mechanics comments about the synthetic fluids valid (I always thought synthetic fluid will be more efficient in all ways over regular fluids)?.

2) If I took the car to my local garage and had the trans. fluid changed to synthetic, will it really void my warranty?

3) Will I see a noticeable drop in temp. in using synthetic?.

4) Should I have the trans. fluid changed with the GMC brand as suggested ?.

PS: I use fully synthetic motor oil and the engine temp has always stayed at 180 deg.

Many thanks in advance.

Titu
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Old 05-03-2007, 10:24 PM   #2
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Quote:
Originally Posted by Titu & Gail
1) Are the mechanics comments about the synthetic fluids valid (I always thought synthetic fluid will be more efficient in all ways over regular fluids)?.
I am not a mechanic, but I don't think so.

Quote:
2) If I took the car to my local garage and had the trans. fluid changed to synthetic, will it really void my warranty?
Only if an warranty investigation can prove that you failed to use a lubrication that does not meet the manufacturer's specification and that directly lead to a mechanical failure. The 1975-enacted federal Magnuson-Moss Act and subsequent enhancements will back you on this.

Quote:
3) Will I see a noticeable drop in temp. in using synthetic?.
I don't know, but I think it likely.

Quote:
4) Should I have the trans. fluid changed with the GMC brand as suggested ?.
Only if you feel it's a superior product to whatever else you can get.

Personally, I'm a fan of Red Line Synthetic oil products; others use Amsoil; still others...well, you get the idea.

I'd go to great lengths to avoid any "extra" additives to any part of your vehicle's lubrication order. They're already produced with a specific additive package to meet the API and manufacture's spec. Anything else you dump in there is likely wasted money...or worse.

Some of my thoughts.

Cheers,
-jd.
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Old 05-03-2007, 10:46 PM   #3
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Part of the cooling system, if you have an aux cooler is the fins and all the road crap and bugs that get lodges in between the fins. My temps always go up when all that junk clogs up the air path. Also one time my temps were higher than normal- I cleaned off the corrosion on the electrical contacts at the sender and all returned to normal. Just facts that occured to me. DG
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Old 05-04-2007, 07:49 AM   #4
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1) Are the mechanics comments about the synthetic fluids valid (I always thought synthetic fluid will be more efficient in all ways over regular fluids)?
Synthetic fluids are less susceptible to viscosity loss due to heat. I use synthetics, am happy with them, and have never had a problem. I do feel they give me a little extra protection, longer service intervals, for a very expensive investment ($50k trucks…). However, I never had any problems related to fluids when I used dino either…

2) If I took the car to my local garage and had the trans. fluid changed to synthetic, will it really void my warranty?
Not if the fluids meet the manufacturer specs. Most brand names do. I understand Amsoil, for whatever reason do not claim that they meet mfr specs.


From 06 GM Owners manual;
Recommended Fluids and
Lubricants
Fluids and lubricants identified below by name,
part number, or specification may be obtained from
your dealer.
Usage Fluid/Lubricant
Engine Oil
Engine oils with the letters CI-4 or
CH-4 are best for your vehicle.
The CI-4 or CH-4 designation
may appear either alone, or in
combination with other API
designations, such as API CI-4/SL.
These letters show American
Petroleum Institute (API) levels of
quality. GM Goodwrench® oil meets
all the requirements for your vehicle.
To determine the preferred viscosity
for your vehicle’s diesel engine, see
Engine Oil on page 5-21.
Engine Coolant
50/50 mixture of clean, drinkable
water and use only DEX-COOL®
Coolant. See Engine Coolant on
page 5-34.
Hydraulic Brake
System
Delco® Supreme 11 Brake Fluid or
equivalent DOT-3 brake fluid.
Usage Fluid/Lubricant
Windshield
Washer GM Optikleen® Washer Solvent.
Van Models:
Parking Brake
Cable Guides
Chassis Lubricant
(GM Part No. U.S. 12377985, in
Canada 88901242) or lubricant
meeting requirements of NLGI #2,
Category LB or GC-LB.
Pickup Models:
Hydraulic
Clutch System
(5-Speed
Trans.)
Hydraulic Clutch Fluid
(GM Part No. U.S. 12345347, in
Canada 10953517) or equivalent
DOT-3 brake fluid.
Pickup Models:
Hydraulic
Clutch System
(6-Speed
Trans.)
Hydraulic Clutch Fluid. Use only
GM Part No. U.S. 88958860, in
Canada 88901244, Super DOT-4
brake fluid.
Power Steering
System
GM Power Steering Fluid
(GM Part No. U.S. 89021184, in
Canada 89021186).
Pickup Models:
Manual
Transmission
(5-Speed
with Low Gear,
RPO MW3)
GM Goodwrench® Synthetic
Manual Transmission Fluid
(GM Part No. U.S. 12346190, in
Canada 10953477) or equivalent
SAE 75W-85 GL-4 gear oil.
6-15
Usage Fluid/Lubricant
Pickup Models:
Manual
Transmission
(5-Speed
without
Low Gear,
RPO MG5)
Synchromesh Transmission Fluid
(GM Part No. U.S. 12345349, in
Canada 10953465).
Pickup Models:
Manual
Transmission
(6-Speed)
Synthetic Transmission Fluid
approved to Allison Transmission®
specification TES-295
(GM Part No. U.S. 12378515,
in Canada 88900701).
Automatic
Transmission
DEXRON®-VI Automatic
Transmission Fluid.
Key Lock
Cylinders
Multi-Purpose Lubricant, Superlube
(GM Part No. U.S. 12346241,
in Canada 10953474).
Pickup Models:
Floor Shift
Linkage
Lubriplate Lubricant Aerosol
(GM Part No. U.S. 12346293,
in Canada 992723) or lubricant
meeting requirements of NLGI #2
Category LB or GC-LB.
Chassis
Lubrication
Chassis Lubricant
(GM Part No. U.S. 12377985,
in Canada 88901242) or lubricant
meeting requirements of NLGI #2,
Category LB or GC-LB.
Usage Fluid/Lubricant
Van Models:
Front Wheel
Bearings
Wheel bearing lubricant meeting
requirements of NLGI #2,
Category GC or GC-LB
(GM Part No. U.S. 1051344,
in Canada 993037).
Van Models:
Front and
Rear Axle
SAE 75W-90 Synthetic
Axle Lubricant
(GM Part No. U.S. 12378261, in
Canada 10953455) or equivalent
meeting GM Specification 9986115.
Pickup Models:
Front Axle
SAE 80W-90 Axle Lubricant
(GM Part No. U.S. 1052271,
in Canada 10950849).
Pickup Models:
Rear Axle
SAE 75W-90 Synthetic
Axle Lubricant
(GM Part No. U.S. 12378261,
in Canada 10953455) meeting
GM Specification 9986115.
Pickup Models:
Manual
Transfer Case
DEXRON®-III Automatic
Transmission Fluid. Look for
“Approved for the H-Specification”
on the label.
Pickup Models:
Automatic
Transfer Case
AUTO-TRAK II Fluid
(GM Part No. U.S. 12378508,
in Canada 10953626).
Van Models:
Transfer Case
DEXRON®-III Automatic
Transmission Fluid. Look for
“Approved for the H-Specification”
on the label.


3) Will I see a noticeable drop in temp. in using synthetic?

Probably not. Whatever tranny fluid you use, once you cook it, you MUST change it asap. Get a gauge if you don’t already have one. This is one way to avoid the problem in the first place. When the temp start to climb, pull over, let the truck idle until it cools down.

4) Should I have the trans. fluid changed with the GMC brand as suggested ?

Again, any fluid that meet the manufacturer specs

p.s. I have had several GM trucks changed to syn fluids, by 2 different dealers. Never had any issues. Some GM vehicles come factory with syn (Vettes). I would talk with the service Mgr, or find a new dealer…

Bill
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Old 05-09-2007, 07:58 AM   #5
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I would be concerned about voiding the warranty unless you can get a service manager to state in writing that he will honor the extended warranty even if you use a non-GM approved fluid. Dextron VI is a semi-synthetic used in all vehicles from GM starting in 06. It is GM approved for use in all previous GM transmissions and is a superior product to previous Dextron's.
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Old 05-09-2007, 09:12 AM   #6
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Quote:
Originally Posted by hiker
I would be concerned about voiding the warranty unless you can get a service manager to state in writing that he will honor the extended warranty even if you use a non-GM approved fluid.
It's already in writing: read your owner's manual.

A vehicle manufacturer may not condition a written or implied warranty on the consumers using parts or services which are identified by brand, trade, or corporate name (such as the vehicle maker's brand) unless the parts or service are provided free of charge. Such warranty conditions are known as a "tie-in sales" provisions.

You cannot void the warranty merely for using any product that meets the published lube specifications -- synthetic or otherwise.

There is substantial federal law covering this, going back for more than thirty years.

Feel free to use the fluid you like best (based on cost, performance, karma, whatever) that meets the specifications, and feel good about it!

Cheers,
-jd.
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Old 05-09-2007, 01:10 PM   #7
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I agree. You cannot void the warranty using syn fluids. GM has syn fluids in many cars and truck. I have syn in nearly every vehicle fluid. So far, the only place I don't yet is my 3/4 ton burb, but that's on the way.

Syn fluid takes a bit more punishment than conventional oils. It is true that even though the syn trans fluid can take a major beating compared to it's conventional counterpart, the reality is that you'll cook the transmission long before you'll cook the syn trans fluid.

I use to be big on Mobil 1, but have since switched to Amsoil. If you pay $20 to become a "preferred customer", you can save that amount and more off retail or their normal website. It's an annual membership.

Most synthetics also flow better in cold as well FWIW.

I say put it in if you feel similarly. This all said, my 1980 Oldsmobeater Delta 88 never had any synthetic and burned no oil when I finally donated the car 2 years ago. Had a very badly rusted out body, but the engine ran like a top. It didn't see as severe service as my tow vehicles got, but I think regular oil changes had something to do with that too.
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Old 05-09-2007, 04:58 PM   #8
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Quote:
Originally Posted by Silvertwinkie
Syn fluid takes a bit more punishment than conventional oils. It is true that even though the syn trans fluid can take a major beating compared to it's conventional counterpart, the reality is that you'll cook the transmission long before you'll cook the syn trans fluid.
Very true. You still want to keep the tranny from operating at extreme temperatures as all the non-metal parts will start to take a beating. It is nice to know though that the superior performance of synthetic will minimize the breakdown by maintaining it's lubricating properties.

Quote:
I use to be big on Mobil 1, but have since switched to Amsoil.
Love their product, hate their marketing. No denying that company founder was a real leader in the field of automotive lubrication. He really was a fighter jock that took the lubricants developed to withstand the extreme temperatures of aviation and applied it to automotive use.

Quote:
Most synthetics also flow better in cold as well FWIW.
Roger that, I can attest to noticeably better start up and cold weather performance.

On the subject of additives I can add (pardon the pun ) that it may be required if you change to synthetic lube in the differential. Even though most synthetics claim you don't need it; my experience, backed up by the diffential shop that rebuilt my limited slip differential is that it is necessary. I didn't (I hope) damage the unit but there was a very noticable performance issue with the Valvoline synthetic until we added the friction modifier for limited slip.

Titu, if you do switch to synthetic I'd be very interested in the temperature readings you get after the change. Please report back.

-Bernie
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Old 05-09-2007, 07:55 PM   #9
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Quote:
Originally Posted by 5cats
It's already in writing: read your owner's manual.

You cannot void the warranty merely for using any product that meets the published lube specifications -- synthetic or otherwise.

There is substantial federal law covering this, going back for more than thirty years.

Cheers,
-jd.
I agree you cannot void the warranty merely for using a product that meets the published lube specifications.

Dextron-III, Dextron-IIIH, Dextron-V, and Dextron-VI are published lube specs. Dextron-VI meets GM specification GMN10060. Any ATF that meets this specification can be used in the transmission without voiding the warranty. GM licenses other manufacturers to produce ATF that meet their standards. I'm certain you will not void the warranty if you use one of these. (See URL for example: http://www.petro-canada.ca/pdfs/IM_8017_E_v14.pdf).

The excerpt from the owners manual in BillTex's post states Engine oil: any oil meeting American Petroleum Institute CI-4 or CH-4 is acceptable (this is for a diesel engine). Hydraulic Clutch Fluid: GM part NO US 12345347 or equivalent DOT-3 brake fluid. But for automatic transmission the manual only states: Dextron-VI. There is no mention of an equivalent.

We know that for engine oils not all synthetics are equivalent. For example, you can't use Mobil 1 5W-20 in a diesel engine. The oil must meet API CI-4 or in 2007 models CJ-4. Using the wrong synthetic will void the warranty.

I'm certain that if you use a synthetic that meets the appropriate Dextron standard for your transmission, you will not void the waranty. You may have to go to court to prove your point but you won't void the waranty.

My point was that Dextron-VI is a GM approved synthetic mix ATF fluid that is superior to what you have in your transmission now. You will not be hassled by the GMC service manager and there will be no question about whether or not the fluid meets GM standards. If you want to upgrade your transmission fluid, to me this seems like the path of least resistance.
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Old 05-09-2007, 08:00 PM   #10
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Quote:
Originally Posted by bhayden

On the subject of additives I can add (pardon the pun ) that it may be required if you change to synthetic lube in the differential. Even though most synthetics claim you don't need it; my experience, backed up by the diffential shop that rebuilt my limited slip differential is that it is necessary. I didn't (I hope) damage the unit but there was a very noticable performance issue with the Valvoline synthetic until we added the friction modifier for limited slip.

-Bernie
My temps pretty much stay the same FWIW, but I will say this, some vehicles need the limited slip additive and others don't.

My Impala SS with the 8.5" rings did. My burb shop book said no additive, I replaced both the rear and the front with synthetic early last spring. One thing to note, that GM after 2000 came out with a TSB for the front GM (4x4)axle stating that vehicles operated in cold climates should use syn in the front diff to the correct viscosities due to chatter as the conventional oil in cold climates was not doing what it needed to in temps like we get here in Chicago. One issue though is that you need to have the right vent cap. I forget which color it had to be, white or black, but one of them is NOT compat with syn. If you do place syn in the front of a 2000-2003 front 4x4 axle (I think the factory made them all compat after 2003) make sure to change the vent plug.

So far no issues with my rear pumpkin with synthetic. But then again, I'm kind of old school. I broke my truck in real easy for the first 3000 miles on conventional and then moved to synthetic. Some agree and others don't. I can see both sides, mine was to wait, then do it.
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Old 05-09-2007, 08:44 PM   #11
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I did a transmission fluid change at 35K on my Allison. Put in 8 quarts of Mobil 1. (Not a complete flush). Changed the front pumpkin with Mobil 1 gear lube and transfer case with Mobil 1 ATF. So now everything is syn except the engine oil, which is Chevron Delo 400. Mobile 1 is to expensive at $66 per oil change.
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Old 05-09-2007, 09:26 PM   #12
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Mobil 1 ATF will save you from early transmission repairs caused by overheating and toque converter wear. My transmission takes 21 quarts and is not cheap to change but beats replacing the gearbox.
Mobil 1 will run cooler and last longer than the manufacturers OEM fluid.
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Old 05-12-2007, 01:09 PM   #13
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Mobil 1 Web Site

I found the following link about Mobil 1 Synthetic ATF on the Mobil web site:
Mobil 1 Synthetic ATF

It states that:

[Mobil 1 Synthetic AFT is] recommended by ExxonMobil for use in 2005 and earlier GM vehicles. Mobil DEXRON-VI ATF is recommended for 2006 and newer GM's and for improved performance in 2005 and earlier GM vehicles.

My understanding of what this means is that Mobil does not recommend Mobil 1 Synthetic for use in GM transmissions specifying Dextron-VI (model years 2006 and greater), and that although Mobil 1 can be used in 2005 and earlier model years, Dextron-VI is preferred.

Am I misinterpreting the Mobil data sheet?
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Old 05-12-2007, 01:59 PM   #14
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I sent you an email earlier in the week about using synthethics. I use it in the engine, trainnie and rear end. I've been through the hot desert in July 05 when at 9 am it was 92 degrees going uphill. 105 degrees going up the mountains to Yosemite. I truly believe if I didn't have the synthetics the truck would have over heated.
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