Shell Dentax S as Synchromesh Fluid.

[George7941]

Here is the Shell transmission oil
http://www.shell.us/home/content/usa/pro...nts_fleets.html

I have a pail of this and it is used at work in MD truck synchromesh transmissions. It is lightweight, being a 50 weight gear oil and it is non EP and therefore safe for yellow metals.

I want to replace the GM Synchromesh Fluid in my Sierra NV3500 transmission. It has 25k mi on the factory fill. Would the Dentax S be a suitable replacement for the GM Synchromesh Fluid?

 

[scoobie]

a bit heavy i would say. i've heard of using 5w30 mobil synthetic in that application. perhaps mix it 50:50 with Pennzoil synchromesh, or 50:50 with ATF.

 

[Doug Hillary]

Hi,
George7941 - Shell's excellent range of Dentax synthetic lubricants have been around for some decades

What is the Sierra's lubricant specification required?

 

[MolaKule]

The Dentax is a PowerShift type fluid and it's viscosity is much higher than GM or Pennzoil Synchromesh.

You would be better served by using one of Redline's or Amsoil synchromesh fluids.

 

[George7941]

Sierra's lube spec for the transmission oil just specifies "Use GM Synchromesh transmission fluid, part no.12345349". I am getting this out of the Owners' Manual. No standards specified that are to be met by the fluid.

Apparently Pennzoil supplies GM with the Synchromesh fluid and the formulation is proprietary, so no other lube manufacturer has a GM approved fluid. Amsoil, Redline etc. come up with recommended fluids thru reverse engineering.

I believe the GM fluid is a synthetic blend, and I am looking for a full synthetic lube. Also, the GM fluid is expensive, at $15/litre.

The replies have convinced me to forget using Dentax. I will go with Amsoil.

 

[MolaKule]

Quote:
Amsoil, Redline etc. come up with recommended fluids thru reverse engineering.


I kinda doubt the reverse engineering statement since the formulations are much different. Amsoil and Redline use a different base oil mix and the additive pack is much different as well.

 

[artificialist]

GM Synchromesh is a 75w gear oil with an API GL-3 rating. I doubt the Shell Dentax S would work here because a GL-1 oil doesn't have enough EP additives to do the job.

RP Synchromax is another option, but you have made your choice, and Amsoil is a fine product.

 

[MolaKule]

Quote:
GM Synchromesh is a 75w gear oil with an API GL-3 rating. I doubt the Shell Dentax S would work here because a GL-1 oil doesn't have enough EP additives to do the job.


Synchromesh is a 9.3 cSt viscosity GL4 fluid.

The Dentax S is MT-1 rated and I'm sure is has plenty of EP additives.

 

[unDummy]

Use an MTF/MTL if you don't want to use synchromesh. Amsoil, Redline, Royalpurple..... have great substitutes.

I've use sae50 manual gear lube in place of 75w/80w-90's GL4.

You'd be nuts to replace a 9cst fluid with a 18cst fluid in the Canadian climate.

 

[George7941]

I will not be using the Dentax S. Only reason I considered it was from a misunderstanding on my part. I thought 50 weight Dentax gear oil was a very light oil, with the 50 weight being a gear oil weight and so considerably lighter than a 75w gear oil. It appears,and somebody can correct me if I am wrong, that the 50 weight is on the engine oil scale and therefore a thick oil. What remains a mystery to me is why Shell would use the engine oil viscosity scale and not the gear oil viscosity scale, considering that Dentax is a gear oil. Perhaps somebody can shed some light on this.