Castrol syntorq v dexron 3

[Joel]

Hoping to change my trans fluid soon and I'm curious to know what the difference is. I think syntorq is a 75/80 but what is the actual spec for this oil since I'm having difficulty soucing it in the UK. Could it be the same as Castrol Syntrax. The syntorq is the factory fill for my trans and although I've considered using Dexron 3, it being an Auto trans fluid has a very low viscosity, so I am loathe to use it given some recent posts on transmission failures under high speed autobahn use. However dexron may be more suitable for conditions where the trans is relatively cool such as the quarter mile. What should I do?

 

[GTS Bruce]

I would hope that the Dublin office of Castrol would be able to answer your questions.If not I am sure Jon B would be more than willing to send you some.I know some racers that used to use auto trans fluid in gear boxes and trans axels.Me too a long time ago.Auto trans fluid will run very hot.Most have switched to a synthetic motor oil or gear lube because they got tired of finding parts destroyed by heat or welded together. Bruce

 

[Kevin ACR]

My understanding from conversation with TTC that makes the transmission is that the Viper and Vette run the same basic trans, different blocking ring material on the viper for more ability to withstand abuse.

I recall him saying that they went from ATF to the castrol in the Viper due to NGR generated behind the V10, can't remember if he said there were other reasons or not.

When I asked if there was anything I could do about the nothchy shifting when the trans is cold I was told that I could run ATF with no downside, with the exception of maybe some noise. I was told the Vette runs ATF .

He really gave no specific recommendation either way for, but did say the factory fill in the viper is intended to be for the life of the trans and didn't require changing as a maintenance item. Also said if I wanted to change it over to ATF I would do no harm, and would probably have easier shifting due to the thinner cold viscosity of the atf over castrol. Felt the ATF didn't offer a shifting advantage over castrol once the trans was warmed up.

fwiw

 

[Joel]

Thanks guys
I got onto Castrol UK tech today. Very helpful lady went to a lot of trouble and got back to me a couple of times. Syntorq is a US only product but is equivalent to Castrol SMX S fully synthetic 75/90 gear oil. I feel very happy about this and have ordered a case of this oil which is quite reasonably priced.
So we'll be changing oil asap, since there was a slight loss of fluid when removing trans for flywheel and clutch replacement
Have to say that I like the thought of a "proper" gear oil rather than dexron even though that is the factory fill for earlier trans

 

[Tom and Vipers]

I'm trying to find if 15-50 Mobil 1 can be used in the Dextron III transmissions. Of course, the 75/80 is even better.

My guess is that the synchros would not work as well. ...and I sure can't see the problem with that! Sort of a poor man's slick shift.