Transaxle fluid specs


jammer

GT Owner
Mark II Lifetime
Apr 19, 2016
165
I want to have all fluids in my 2006 GT replaced. Local Ford dealer wants to use Redline 57905 75W90 Synthetic for transaxle fluid and DOT 3 for brake and clutch fluids. Owners Manual and the experts here call for XT-75W90-QGT for transaxle and DOT 3 for brake and clutch (Motorcraft 5.1 here). I can go with the DOT 3 dealer recommendation because it is inline with the OM, but I'm having hard time accepting the Redline 57905 in the transaxle even though both meet the API GL-5 specs. What do you guys think? TIA
 
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Specracer

GT Owner
Mark IV Lifetime
Nov 28, 2005
7,081
MA
I used the Motorcraft trans fluid. I would be more interested in having a better brake fluid. The stock fluid is nothing special. Ive used SRF which no longer seems to be available. Now using Motul.

A handy chart showing wet boiling points and prices

 
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nota4re

GT Owner
Mark IV Lifetime
Le Mans 2010 Supporter
Feb 15, 2006
4,177
I think you are correct to be concerned. I would never put anything other than the XT-75W90-QGT fluid in the transaxle. The the best of my knowledge, Ford has never stated "or equivalent" - so I would ONLY use the OEM spec fluid.
 
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HighHP

GT Owner
Jun 3, 2019
434
Spokane, WA
I am not aware of a Redline product number 57905. They do have a 57904 that matches your description. This is for use in limited slip differentials. The added friction modifiers in this oil do their job too well related to transmission gear synchros, it causes them to slip and not grab the gear when you shift gears. Also, most GL5 lubes have extreme pressure (EP) modifiers for the ring and pinion gears and should not be used in transmissions. These GL5 modifiers tend to corrode yellow metals (copper based brass synchros) present in transmissions, thus GL4 rated oils are typically used in transmissions. However, some oils that are made specifically for transaxles are rated GL5 for the ring and pinion, but also are safe for the yellow metals, due to the addition of copper corrosion protection additives. The Ford recommended oil is GL5 rated and rated for the transaxle. Redline has a product that is probably superior to the Ford product, is rated GL5 and is formulated for transaxles. It is product number 58304, Red Line 75W90NS GL-5 Gear Oil. It is rated for Porsche, Ferrari, Subaru transaxles. See tech sheet attached.

I dearly wanted to run this Red Line oil, but, the consequence of problems later is $$$$$$ and more $$$$$$. I stayed with the Ford Product.

PS: Just found the 57905. It is the same as 57904 (Qt), but in a gallon size. Don't use it!!!!!
 

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PeteK

GT Owner
Mark II Lifetime
Apr 18, 2014
2,268
Kalama, Free part of WA State
HighHP: Thanks for the info sheet on the Redline. I'm about due for a trans oil change. I've used the Ford stuff up to now. Given what they say about reducing friction in the sliding of the hypoid gears, and thereby reducing temperature, I'm tempted to give it a try this time.
 

HighHP

GT Owner
Jun 3, 2019
434
Spokane, WA
Red Line uses superior base oils, not refined crude oil based. I don't race my GT so gear to gear contact temps don't get that high. If I raced it, I would run the Red Line. Another plus is that it is available for less than 1/2 the price.
 
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Beez

GT Owner
Mark II Lifetime
Oct 28, 2016
195
South Denver
I find it surprising that a Ford dealer would recommend anything other than the Ford specified product. I had to learn more than I ever wanted to have to know about fluid choices in our unique and expensive transaxle, after needing to work through a repair.

Regardless of any tempting "on-paper" technical advantages of the Redline, subtle additive differences can have unintended consequences. Many Getrag 6 spds in MKIV Supras were damaged by "superior" Redline products having additives that caused seal-swelling. I do not mean to imply that specific issue would be a risk in our Ricardo application, but it is a general example of why I can't imagine risking use of anything other than XT-75W90-QGT.

Also if I was a future buyer seeing a receipt for service done with a non-OEM non-recommended fluid, I'd be uneasy and think that was an odd-ball thing to do.
 

jammer

GT Owner
Mark II Lifetime
Apr 19, 2016
165
Beez,

I too don't understand why a Ford dealer would use after market product when Ford product is specified. Maybe they don't have it in stock and too lazy to order and wait for it?

In my search I came across your thread from couple of years ago and learnt a lot about the importance of using the correct transaxle oil. That's what made me question the dealer's recommendation. So I thank you and thank all those who diagnosed, explained and helped solve that issue and those who responded here.
 
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lewishou

GT Owner
Feb 27, 2007
26
Atherton, CA
Mind sharing which dealership in the Bay Area you are using? Thanks.


Lewis


Beez,

I too don't understand why a Ford dealer would use after market product when Ford product is specified. Maybe they don't have it in stock and too lazy to order and wait for it?

In my search I came across your thread from couple of years ago and learnt a lot about the importance of using the correct transaxle oil. That's what made me question the dealer's recommendation. So I thank you and thank all those who diagnosed, explained and helped solve that issue and those who responded here.
 

jammer

GT Owner
Mark II Lifetime
Apr 19, 2016
165
After my talk with the service manager at Livermore Ford he contacted Red Line tech support. They confirmed to him that Red Line 57904 is not suitable for the GT transaxle and that Red Line 58304, 75W90NS is what should be used instead. Basically what HighHP said above. I am satisfied that he genuinely but mistakenly believed that the Red Line 57904 was a superior product to the Motorcraft oil and wanted to do the right thing. After checking with Red Line he confirmed that the Ford specified Motorcraft XT-75W90-QGT will be used in my transaxle.