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Discussion Starter #1
Ok, I was going to put this under the other thread but was afraid some of you would not see it as that thread has gotten quite long.......there is NO comparison between the RP Synchromax and the RP max_gear; the synchromax is way better; the Max gear is maybe 10% better than the stock fluid but still is difficult at times to shift 1-2; any other thoughts now, Folks were saying try the redline but I thought it did not have the modifiers(NS) for non slip? so is that ok, as you all recall I went back to Max GEar after you guys as did RP told me that the Synchromax was not intended for our tranny's......can I mix the two, lol dogdoc
 

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So are you going back to Synchromax? Will the LSD really suffer during normal driving? If you track the car every month I could see a problem arising.
 

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Discussion Starter #3
Not for now

no one can give me a straight answer for the long term, the Ferrari tech said they use it alot and he believes it will not hurt the tranny, but he has no long term history he says to check years later, RP said it won't hurt but they do not recommend it since it is not what Maserati calls for..........a dilemma, read the long thread on the clutch adjustment.........
 

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Thanks for the report. It would certainly haunt me to run 10W (eg Synchromax) lube in a gearbox that calls for 75W90 (eg Max Gear). I had suspected that such would be the result.

I have purchased 3 quarts of the Redline 75W90NS, which does not have the friction modifiers that foul up the synchronizers. Most all 75W90 gear lubes have these. I'll give a report as soon as I get it in service. It'll have to wait a bit as my son is doing an engine rebuild in the garage right now.

We face a dilema in having a synchromesh gearbox sharing fluid with a limited slip differential. I know the Mitsubishi 3000GT guys have similar issues. Anyway, I feel we can get to a solution.

I expect we will find nirvana by using Redline 75W90NS and adding a small amount of friction modifier, but much less than the 5% that most gear lubes contain.

Again, thanks for the data, Dogdoc!
 

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Discussion Starter #5
How do you know how much to add?

That's why I asked can you mix the two? what is the name of the modifier product and in what quanity, let me know, thanks, dogoc
 

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You can find the friction modifier at http://www.redlineoil.com/products_gearlubricants.asp?productID=41&subCategoryID=15&categoryID=6

However, the problem with Synchromax is that it is 10W oil that is not designed for the stresses of the hypoid gears of the differential. That calls for a GL-5 rated gear lube. The friction-modifier needs of the limited slip clutches are a secondary consideration.

Most gear lube has 5% limited slip friction modifier. For our cars, I suspect the amount should be anywhere between 0% to less than 5%. The folks at Redline suggest using the NS lube and adding modifier (if needed) just until the limited slip clutches no longer "growl" or "chatter".

There are two negative effects that gear lube can potentially have on synchronizer operation. First is lube that is too thick which clings to the cone and creates a cushion barrier to the cone engaging the gear. Secondly, friction modifiers can make the lube too slippery, preventing the synchro cone from having enough friction to bring the gear up to speed. That seems to be what is happeneing to second gear in my trans, as I get some mild clashing of the slider with the gear.

In answer to your question, I have heard of people mixing gear lubes but I've never heard how it turned out for them.
 

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Discussion Starter #7
Post results please!!!

Let us know when you change the fluids out and what the mix ratio was, sounds like you think you may not need any, maybe I should go the redline? Post the exact Product name again please........Dogdoc
 

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Redline Gear Oil 75W90NS

if needed, Limited Slip Friction Modifier

Both items can be seen on the link I posted above. I hope my son gets this dern hot-rod motor built and installed this week so I can have the garage back this weekend.
 

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Discussion Starter #9
How much will you add?

How do you determine what amount of the modifier to add to the 3 bottles of 75W90? Dogdoc
 

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The idea is to start with none. If you hear "growling" or "chatter" from the limited slip, add a bit of friction modifier. If you still hear the unwanted sound, add a bit more. Keep adding in increments until the "growling or chatter" goes away. I plan to add 30ml or about 1% at a time, if needed. Maybe once I start, I'll try 15ml at a time to get a more exact minimum.

If I still have bad shifting with the 75W90NS and no friction modifier, then I'll consider trying a thinner lube, like a GL-4 motor oil weight. My guess is that won't be the case. Knowing what I know about how challenging it is to repair/replace hypoid gears, I will not go to a 10W oil in any case.
 

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Mt90?

I checked my owner’s manual (04 Spyder) and it says “GL4/GL5” ?? so I phoned Red Line to clarify. They seemed to lean towards MT90 GL4 or 75W90GL5. They said that the GL5 had inherent resistance to high pressure degradation (re: caused by pressure in hypoid gears) and in fact recommended against mixing the friction modifiers to the 75W90NS – too much risk of problems on the synchro side and no real protection against the hypoid gear wear. That being said, they said that the concentration of sulfur in the GL5 was so low that it would cause no problems to the synchromesh bushings.

My mechanic says to go with Amsoil GL4 – he says in 25 years experience the Red Line lubes always cause the shifting to be worse (no mention of the effects on the differential though).

I have no idea what to think now!!
 

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I also corresponded with Redline. It was they who suggested 75W90NS as best for this application.

I have now drained the Mobil1 from the gearbox and installed the Redline 75W90NS with no friction modifier. I find no growling or chattering from the limited slip clutches even though there is no friction modifier in there. The synchros engage better so I no longer get that brief "bump-bump" clash in the 1-2 shift. Overall, the shifting is better but still notchy as hell on the 1-2 shift and less so on others. I only have about 40 miles on this lube and think I'll give it a bit more of a test before the final decision.

If the owner's manual says GL4 is OK, I will give the GL4 a try. Since the lack of friction modifier doesn't look to matter anyway, this may flow out of the synchro cones better.

The shifting is the only low point in the total enjoyment of this car and I feel sure that it can be made to be all that it should be. Flashgordon, if you try the GL4, please let us know how you find it.
 

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Discussion Starter #13
I started this thread and it is long!

so keep me in the loop; looks like many of us have the same concern; will be waiting on results!!!
 

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GL4 Transaxle Oil

I am scheduled to take her in next week (weather permitting). I will try the Amsoil GL4 and I will let you know Fastfreddy (plus others).

I am also switching out the Motul 300V 15W50 engine oil that my last mechanic put in (despite the manual calling for 5W40). This is way too thick for weather in the 20’s. I am going with Shell Helix 5W40. My mechanic is also going to adjust the linkage and cables on the shifter – I will advise on how that works.
 

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Discussion Starter #15
Fast Freddy, where R U on the Redline?

How is the shifting on the redline; give us an update please!!!!!!!!!
 

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Follow Up

Guys,

The weather here (Calgary) is stll a bit iffy. Last week was still too snowy to get the car in - hopefully next week. I will advise as soon as I can.
 
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