Question 1

Can you mix gl-4 gear oil with gl-5 gear oil? what is difference? if do 50/50....will be good together? why or why not?

Accepted Answer

NO NO NO...  GL-4 is specific for older transmissions that have bronze/brass parts. GL-5 will DESTROY these parts.. believe me I know from experience. My local speed shop mistakenly gave me GL-5 for my 91 YJ with the X-5 trans.  Within ten miles I could smell the problem happening. They honored the mistake and gave me a gallon of correct GL-4 so at 150K my X5 was shifting much better. It's in the shop now at 185K for a trans rebuild (yeah it lasted THAT long) and Troy Transmissions was pleased to hear I wanted Redline. He insists on synthetics for Arizona heat and drivers who get in extreme conditions, look up the "back way to Crown King" for an idea of our kind of fun.  And a heads up for the Y owners... beware the fast lube places.  I went to two different shops and BOTH insisted GL-5 was the correct lube!!!  NOT! Luckily the $450 they wanted just to change fluids scared me off and I did what Jeepers should do... work on your own rig yourself.

Question 2

why do many say to not change the old gear oil & that the "gunk" in old gear oil makes transmssion last longer & might have problems with new gear oil

Accepted Answer

What they are referring to is automatic transmission fluid. Automatic transmissions have a series of "bands" with clutch like materials bonded to the friction side. On a worn out automatic transmission, the friction materials on these bands are already smoothed out and slip. Since automatic transmission are driven by hydraulic pressure, the "gunk" suspended inside old fluid will help with "gripping" action with these band. This redline gear oil is used in Manual transmissions. The old saying would not apply here.

Question 3

Is MT 90 good for a 1995 jeep yj manual transmission?

Accepted Answer

Yes, great product; bought the vehicle used and it was not sure what  type of fluid it had in the transmission. The jeep sounded like a bus and once I added the MT-90; big difference and most importantly much quietly.

Question 4

Is this product compatible with my 1975 vw beetle, type 1 which spec's 85w/90 gl-4 gear oil? or do you have a synthetic product that is?

Accepted Answer

I would look on the Volkswagen site or call a Volkswagen service department you can fool around with weights on engine oil but I wouldn't put the wrong weight in on a transmission

ASIN	B002INX20C
Amazon Bestseller	#425,861 in Automotive ( See Top 100 in Automotive ) #487 in Gear Oils
Brand Name	Red Line
Container Type	Can
Customer Reviews	4.8 4.8 out of 5 stars (1,554)
Global Trade Identification Number	00083522503051
Item Weight	2.27 Kilograms
Liquid Volume	128 Fluid Ounces
Manufacturer	Red Line
Material	Synthetic
Model Number	50305
Number of Items	1
Part Number	50305
Recommended Uses For Product	Lubricant
Specific Uses For Product	Manual transmission and transaxle
UPC	083522503051
Unit Count	3785.41 Milliliters

Red Line MT-90 Gear Oil 75W90 GL-4 1 Gallon (128 Ounces) 50305

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