Does anyone have first hand experience with either of these lubricants? I was considering using AMSoil transmission oil on my 3 speed but Royal Purple is much more available here. I got the AMSoil brochure at a local car show and it impressd me, but I would like to hear some feedback and personal experiences from real people. I'm also open to recommendations of other brands. Obviously my goal is to provide the longest possible life and least wear on my 3spd and overdrive unit because far down the road replacement parts might be even harder if not impossible to come across. I have just finished rebuilding this transmission and want to do it some good. Thanks for any input!
Mike

 

You're fine to use ANY synthetic gear oil in your transmission.

I have used Amsoil System 3000 synthetic oil in my VW transmission and it was MUCH better than the regular gear oil. Especially in very cold weather.

I also use it in my rear axle. I was getting it from a friend who is an AMSOIL dealer.....so I got it for his cost. It was still a little more than going to Walmart etc and getting Mobil1 gear oil.

Next time I'll just get the Mobil 1 at Wallys World.

I don't think it really matters which brand.



Regards,



Rick

 

We use Redline in our tranny and rear ends on the race cars (mostly due to availability). All the brands mentioned are equally as good. be sure to get the right weight and type, then buy based on price.

 

Do either of them make straight 140 weight oil, GL-1 or GL-2? That's what the 3-sp's use. Don't forget the OD has a separate reservoir, too.

 

I've used the Royal Purple just because I saw Chip Foose using on his truck and all the others he builds. The stuff is very expensive, but definitely seems to be good stuff. It may be my imagination, but things seem to be running quieter. more efficient and smoother? I also bought the gear oil for the rear end with Royal Purple, but I only found 90W and that's what I'm using.

 

Can I use 75/140 or 80/140? I'm having trouble finding straight 140wt.

Mike

 

Albuq,
Are you sure it uses 140? The operators manual says 80w below 32degrees and 90w above 32.

Mike

 

What year and make 3 speed is it? All the early ones i.e. 1975 and earlier that I know of used straight 90W gear oil. I've never seen 140W that would be like tar.

 

Actually i have seen 3 independent studies all with dynos all took diffrent cars one was a High perfomance nova one was a street comuter and dont rember the third but all 3 showed a slight gain in hp and milleage

They changed every fluid in the car with Royal Purple though not just the engine or tranny.

 

Its a LD 3spd overdrive from a 59 F-100. I'm pretty sure its 90w, thats what the owners manual state.
Mike

 

Well, mine is a '52, and the '48-'52 shop manual shows straight 140 for Summer, lightweight 90 for winter. (for the trans)

Interesting, I wonder if there are any parts changes that resulted in the later models having thinner oil.

The usual sources for straight 140 are farm stores, construction equiopment stores, or NAPA (special order most places)

 

Thats interesting. Whats the difference between straight 90 and say 75w90? Most of the sythetics come in 75w90 or 80w90. Will either one work the same?
Mike

 

Obviously 75w90 will be less like molasses in cold weather, but runs off surfaces a little quicker too. If your spec is for 90 in summer and 75 in winter, I'd say you're OK with 75w90 year round. But look for GL-3 spec 75w90....

The real issue with multigrades this heavy is that most dealers only carry GL-4 or GL-5 spec multigrades. To get hypoid gear compatibility and wear ratings, they put stuff in GL-4 and more so in GL-5 that attacks copper-bearing metals at elevated temperatures. Personally I doubt it's an issue unless you are going down the highway at high speeds with a load in the bed, but I've heard horror stories!!! Like synchro blocker rings disappearing in a couple months....

It just can't hurt to use what Henry designed 'em for!

 

If you go to Wal Mart, they have both 90W and 140W in gear oil. Not the synthetics you guys are talking about here though.

The grade 75W -90W only means that when the oil is cold at start up, it will be a 75W grade, when the temps go up it will thicken to a 90W. You can you that grade and it will be fine.