Engine/Transmission (1998.5 - 2002) Gear Oil Question (yet another)

[mavrick1]

I've got a question concerning gear oil. My truck has 35000 miles on it and I recently changed the rear diff oil and put on a Mag-Hytec cover (which I love). I'm a Valvoline guy so I put Valvoline SynPower Full Synthetic SAE 75W-90 in it (a lot of folks on here have said full syn 75W-90). It is MIL-PRF-2105E and API GL-5 and MT-1. The owners manual says SAE 90 GL-5. The service manual says the same with MIL-L-2105C. At 30000 I had the front axle oil changed by the dealer because the passenger side seal went out (warranty covered), so I don't plan on doing it for a while. But when I do I plan on using the above Valvoline and putting on a Mag-Hytec cover. My biggest question has to do with the 5 Speed NV-4500 transmission. The owners manual says 75W synthetic API GL-4 and the service manual says Mopar manual transmission lubricant (lot of help there) and the PTO cover says Castrol Syntorq. I called the dealer and the guy said the Mopar stuff is $26 a quart, but he also sells and recommends the Mobil 1 for $9 a quart (I have seen this stuff mentioned on TDR). Since I said I prefer Valvoline and would like to use the same in both axles and transmission, is there a big difference between the Valvoline and Mobil 1? I've seen mentioned here that GL-5 shouldn't be used in the transmission. What is the difference between GL-4 and GL-5 and between MIL-PRF-2105E and MIL-L-2105C, and would the Valvoline be ok in the transmission?

Thanks for any help on this,

Lance

 

[dremelts]

Mavrick1,



There is an article in a previous issue of the TDR magazine that covers fluids. I think the difference between the GL-4 and GL-5 has to do with the amount of phosphates (GL-5 has more) which can plate your synchros when they get hot and reduce their friction making it hard to shift.



I don't know believe the article went into what the differences are between the two MIL specs you mentioned, but it did say that the GL-4 stuff is available from Standard Transmission.

 

[gonehuntingagain]

The Mopar manual transmission fluid is re-labeled castrol syntorq.

I replaced my fluid with Amsoil GL-4 80w-90 and added a transmission filter. What a difference in shifting! Much smoother and easier shifts.

 

[TowPro]

The castrol Syntorq you and I can buy at the store is not the same thing used in our trucks.



The 5 speed requires GL-4

the amsoil you used is called AGT which looks to me like it should fit the bill. If you call Amsoil they will recomend Series 2000 TGR which is GL-5, but they will tell you that the trans don't get hot enough to have the problem. All I know is I put the series 2000 in and could smell hot gear oil every time I backed my camper into a camground.



Now I am stuck with an auto for 5 years (but I got a great deal ) so we will see how that works out.



If I did it again, I would just call Standard Transmission and get the correct stuff for a couple more dollars.



don't get me wrong on the Amsoil, I still use it lots of places, I just think the application was wrong.

 

[jrollins]

i personally used the 75W full synthetic gear oil that is the house brand for Orliey auto parts, it comes in like 2 qt bottles and is a half as much as the DC stuff. I changed it around 95 to 100k and am about to roll over 126 with no problems, the trans. is hard to shift at times but it was like that before the fluid change and for 126k i am not really complaining much.