GL3 vs GL4 or 5 differential fill?

I'm refilling the differential this morning getting ready to pull the beast out of the garage under it's own power (fist time this has happened since 1989!).

I found nothing in the archives when searching for GL3? Is it OK to use the GL4 or 5 rated hypoid oil or should I worry about bronze parts in the 75B rear gear?

TIA
Cheers,
Newt

Newt, love the color ! I dont know about the G #s you mentioned but I use Castrol Hypo 90w gear oil.

Thanks Robert, I mixed that color myself actually... the kid can't shoot a car for a hill of beans but he can blend colors? IF (if being the operative word here) I actually get the beast out of the garage today I'll post some photos. Living in PA the state requires 4 photos of the finished car for the antique plate application. I'm nowhere near being ready to put the car on the road but I didn't want to take the photos with the car in the garage on jack stands... that makes them suspicious! LOL

Cheers,
Newt

Good luck! Yep, like the color. Good job on the mix.
Rob

Jim,
I have been using Mobil 1 75w-90 gear oil in my rear end for several years now and the only problem I have ever had with it is synthetic's propensity to sometimes weep past the rear axle seals.

I fixed that by using an alternative double lipped seal, either "County" brand part number CNA294 or NOK UH0577-E0 BD , http://www.afmusa.com/doc_generator.asp?doc_id=979&attr_index_id=4130 which use a nitrile coated seal housing.

GL4 would be the right one from a rating point of view, but GL5 will work too. The API defnition for GL5 says that it is compatible with yellow metal. If you use GL4 look for one that says on the label that it is compatible with yellow metals.

Thanks for seal tip Bob! And the lead on labeling Mark! I'd like to keep costs down on this driver as much as possible and I'm hoping the seals DON'T leak! I just went ahead and used the Hypoid I get from TRF. I had two quarts of it here anyway (thought I was out!). Then I went in and actually read the labels on the two gallons of gear oil I have here. I have a NEW gallon of GL4 that I got for the GT6 and has the yellow metals statement. (thought I was out again... must be old timers!) The other was GL5 so that goes in the truck! No loss, the TR3 gets the fluids changed in a couple of weeks anyway!

Thanks again,
Newt