75w90 gl5 in t5

[JT1]

My buddy just rebuilt the t5 in his 302 powered ranger and filled it with supertech synthetic 75w90 gl5 gear oil under the advice of one of the dealership mechanics he works with. I immediately warned him of the dangers associated with using a gl5 lube with brass synchros, yet he decided to use it anyway. Has anyone ever had any first hand experience with said issue?

 

[salv]

The AX-15 in my XJ called for 80w90 GL-3 from the factory, and the shift quality sucked with it. It is now back speced to run on a GL-5.
The NV3500 that replaced the AX-15 runs synchromesh.
I drained and filled with synchromesh. The AX-15 shifts much better. No issues.
If synchros are your primary concern, go with synchromesh. It will adequately lubricate the gears.

 

[Rand]

its not the end of the world if the proper gl-5 lube is used but gl-4 would be much better in that application.

 

[ethangsmith]

All world class T5s (All T5's after about 1985) take Mercon/Dexron III fluid. Do not fill them with gear oil! You'll end up with hard shifting and potential synchronizer issues. Check out any 79-93 Mustang forum and do some searches. The earlier T5s specified gear oil, but it was switched to Dex/Merc shortly after their introduction. There is even rumor that the gear oil specification was an error in Ford manuals since the T5 was the first manual transmission to use ATF instead of gear oil. Regardless, you'll get MUCH better shifting out of it with an ATF fluid.

 

[JT1]

I should mention its non world class.

 

[ethangsmith]

Then you should be ok. It will shift hard in the winter though with the gear oil in it. I've heard GM's synchromesh fluid performs well in them FWIW.

 

[mechtech2]

The GL5 is probably buffered. That means the sulfur is neutralized to not corrode the synchros.
I don't know who makes over the counter non buffered GL5 anymore.

But it is a differential lube, not a dedicated manual trans lube.
It is not optimized for shifting, and is a bit thick. Being thick is felt more when cold, , esp in winter starts.

ATF has it's own inherent problems with manual trannys.
Synchromesh fluids have been used with great success.
It depends on it's use and how and where you drive.

 

[JT1]

Good to know that the gl5 wont cause damage to the freshly built trans. I havent driven the truck myself, but according to him it shifts wonderfully and probably wont be driven in the winter.