GL-4 vs GL-5 gear oil

Hello all, I'm getting ready to change the gear oil in my TR250 non o.d. tranny & diff, The owners manual specs GL-4. I've done a little research & it seems as though you do need to use GL-4 in the TR's due to the bronze components. I couldn't find anything in Valvolines page, but here is something from Penzoil. Note the comment about "bronze components" The GL-5 spec does not mention it.

It appears as though synthetics cover GL-GL5 applications.

Any comments, experiences??

https://www.pennzoil.com/products/gear_oil/gearplus8090g4.html

Two years ago when I changed the oil in my Spitfire 1500's transmission I used Quarter State's synthetic GL-4 gear oil. I used this oil because it was the only one I could find that said that it was a GL-4 oil. The transmission has worked very well since changing the oil, it even shifts easier. The only problem is that it comes in US quarts, not Imperial quarts, so I had to buy two bottles. /ubbthreads/images/graemlins/canpatriot.GIF

Does anyone know anything about spitfire transmissions blowing oil out of the breather? It seems mine keeps getting low, but it barely (it does indeed leak, but hardly at all when sitting) leaks ... it would seem it blows out when driven... any way to prevent that?

Matt:

I've never seen this. Are you sure that the top cover plate in the trans isn't loose or missing bolts? Also, I think that the vent/breather in that plate has a screen to keep oil from sloshing out. Is your's damaged in some way?
Also, be sure that regular motor oil was not put in the trans by mistake. Older Spridgets with the ribcage trans use motor oil (instead of gear oil), so it's a common mistake.
The Red Line Gear Oil is my favorite (see Dave R's post in this section about Red Line).

Nope, most definitely gear oil, put it in myself, then filled it again after about 750 miles ... SilentUnicorn (Mark) had commented on this problem also, so I don't really know... Perhaps installing a catch tank is in order, to see if that is truly the culprit ... but the cover is installed securely (did that one myself, also, and I am certain that it is still in place after about 1250 miles total).

Finally got an answer back from Valvoline:
can't be too carefull!

Product Information A PRODUCT OF THE VALVOLINE COMPANY A DIVISION OF ASHLAND INC. VALVOLINE HIGH PERFORMANCE GEAR OIL Valvoline High Performance Gear Oils are superior sulfur-phosphorus, extreme pressure gear lubricants formulated with premium quality basestocks to meet the demands for excellent performance. It is designed to provide excellent load carrying capacity, extreme pressure properties, anti-foam performance, demulsibility, corrosion protection, thermal stability protection, and service fill limited slip capability. These products are recommended for conventional rear axles, limited slip rear axles, and transmissions requiring EP gear lubes under high speed, high load, high torque, and high horsepower conditions. Valvoline High Performance Gear Oils meet or exceed: Ford M2C108C; Mack GO-H, & GO-J; Mil-PRF-2105E; API Services GL-5, GL-4. The Valvoline High Performance Gear Oils Advantages:
Thermal Protection: Provides outstanding thermal stability for cleanliness and longer service life.
Wear Protection: Contains additives to assist in protecting gear teeth against pitting, spalling, and scouring.
Reduces Chattering: Contains special additives to reduce chattering in limited-slip differentials.
Corrosion Protection: Protects parts from rust and corrosion. Approvals/Performance Levels Viscosity Grade/Other MIL-PRF-2105E - - - - - -, 80W-90, 85W-140 API GL-4 75W-90, 80W-90, 85W-140 API GL-5 75W-90, 80W-90, 85W-140 FORD M2C108C - - - - - -, 80W-90, 85W-140 API MT-1 75W-90, 80W-90, 85W-140 Test 75W-90 80W-90 85W-140 Vis @ 100
C (cSt) 15.5 14.5 26.7 Vis @ 40
C (cSt) 86.91 141 361 Viscosity Index 190 98 99 Spec Gravity @ 60F 0.887 0.900 0.904 Density (lbs/gal) 7.39 7.49 7.53 Brookfield Vis., cP 140,000(-40C) 125,000(-26C) 120,000(-12C) Pour Point, C -39 -27 -15 This information only applies to products manufactured in the following location(s): USA, Canada. Effective Date: Replaces: Author's Initials: Code 07/08/03 07/29/98 DJD

Kind of hard to sort out just what Valvoline is saying. Sounds like an advertising snow job.

Straight GL4 is intended for transmissions. Especially those which have bronze parts in them. It is a medium load capacity lube.

Straight GL5 is intended for hypoid axles. It has a large amount of extreme pressure additive (sulfur compounds) The sulfur in GL5 will degrade bronze parts in a transmission.

The GL4/GL5 combination oil is a synthetic. Due to the synthetic characteristics, it requires much less of the EP (sulfur) additive & will work in both transmissions & axles.

It would be bad to use a straight GL5 in a transmission, or straight GL4 in an axle. The GL4/GL5 is good for both.

Redline MT90 & MTL are GL4 transmission oils which are formulated to have the correct friction coefficient to make synchronizers work well.

Redline has other oils with the GL5 rating for axles, such as 75W-90 NS.
D