I am flushing my tranny (manual) and the rear. I wanna put royal purple in. Can i use the Royal Purple Synchromax in the tranny? What weight does our cars need in the rear? 75-90 or 75-140?
The car: 06 GT
The car: 06 GT
Help!! What gear oil should i use?
- Thread starter Slipk911
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Just did this exact same thing on my 08 GT. I used Royal Purple 75W140 with NO friction modifier added in the rear axle. It completely cured my minor gear whine. I also changed the 5 speed out to Royal Purple Synchromax and I love it! It shifts much better when cold and is absoloutely silent in operation. I plan to stick with Mobil 1 in the engine but this Royal Purple gear oil is good stuff! 
When you say wheel slippage in turns, do you mean that the car acts more like it has a solid axle? Will this harm the rear down the road?
I think you're mis-understanding how the limited slip and friction modifier are supposed to work. The friction modifier is added to make the fluid slippier so the clutches in the lim slip won't bind or grab in corners and NOT allow the inside wheel to turn without binding. ANY rear axle will spin the inside wheel in a corner in the rain if you mash the gas. Royal Purple advertises that you don't need to add it to their fluid so I didn't. So far in 500 miles of driving the lim slip acts just like it did on Ford fluid so I think it's fine. Again some lim slips will grab and bind without the modifier but spinning the tires in the rain is not a symptom of this.
I think you're mis-understanding how the limited slip and friction modifier are supposed to work. The friction modifier is added to make the fluid slippier so the clutches in the lim slip won't bind or grab in corners and NOT allow the inside wheel to turn without binding. ANY rear axle will spin the inside wheel in a corner in the rain if you mash the gas. Royal Purple advertises that you don't need to add it to their fluid so I didn't. So far in 500 miles of driving the lim slip acts just like it did on Ford fluid so I think it's fine. Again some lim slips will grab and bind without the modifier but spinning the tires in the rain is not a symptom of this.
I had wheel spin with very mild throttle. I know how the diff is supposed to react from the 1st 35k miles I put on the car. I believed the advertising too and didn't think I needed the 6$ friction modifier. I was wrong.
GOLDENPONY
Founding Member
Oil
I am using Syncromax, very satisfied. The rear end wants 75W140. Use 1 bottle of Ford friction modifier.
I am using Syncromax, very satisfied. The rear end wants 75W140. Use 1 bottle of Ford friction modifier.
gmantheman
Member
Hey guys,
I had my gears swapped from 3.31 to 4.10's in my auto. At higher speeds, and not all the time, but at certain rpm's, I will hear a slight high frequency noise, almost like a whistling sound coming from the rear. I'm not toooo sure the type of gear oil that was used, but does this sound like a mis-alignment issue or that the wrong type of gear oil was used (75-90 instead of 75-140)? It's not annoying at all, but it's noticeable. Just curious.
I had my gears swapped from 3.31 to 4.10's in my auto. At higher speeds, and not all the time, but at certain rpm's, I will hear a slight high frequency noise, almost like a whistling sound coming from the rear. I'm not toooo sure the type of gear oil that was used, but does this sound like a mis-alignment issue or that the wrong type of gear oil was used (75-90 instead of 75-140)? It's not annoying at all, but it's noticeable. Just curious.
ptfoxbdy89
New Member
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