What viscosity is this particular oil?

Film thickness greater than an SAE 75W250, yet low fluid friction like 75W90For heavily-loaded racing differentials and transmissions, problem gearboxesMany performance racing applications like Sprint/Midget/Dirt Late Model Differentials, Detroit Lockers and spools, NHRA Top Fuel and Funny Car rear endsNot recommended for most synchro applications due to the product's extreme slipperiness

What is the viscosity of this? Need a specific number.

Film thickness greater than an SAE 75W250, yet low fluid friction like 75W90. This is from the manufacturer's site.

Canged primary chain OIL of my 2002 RoadKing ScreamingEagle I made a MISTAKE! Added REDLINTransFluidw/Shockproof. IS It COMPATABLE

I would think not. As the primary runs a 20w 50 and the red line is something like 75 90 it's going to a lot thicker. I would call a local Indy not HD and ask them for sure.

It exceeds API GL-5 specifications.

58204 Heavy Shockproof Gear Oil 1 Quart Bottle

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Description

⚡ Shift into high gear with Red Line’s shockproof power!

EXTENDED SERVICE LIFE - Designed for longer drain intervals, saving you time and maintenance costs without compromising performance.
TRUSTED LEGACY SINCE 1979 - Red Line’s uncompromising quality ensures your vehicle performs at its peak, race after race.
RACE PROVEN SYNTHETIC FORMULA - Engineered from advanced polyol ester base stocks for unmatched lubrication under extreme conditions.
MAXIMIZED DIFFERENTIAL EFFICIENCY - Boosts mileage and reduces wear, exceeding API GL-5 standards for superior drivetrain protection.
SPECIALIZED SHOCK PROOF PERFORMANCE - The go-to gear oil for high-demand racing setups including Sprint, Midget, and NHRA Top Fuel rear ends.

Red Line 58204 Heavy ShockProof Gear Oil is a fully synthetic, polyol ester-based lubricant designed to deliver exceptional protection and efficiency for high-performance differentials. Exceeding API GL-5 specs, it extends drain intervals and reduces wear, making it a top choice for racing and specialty applications since 1979.

Specifications

ASIN	B000CPI5XW
Best Sellers Rank	#12,204 in Automotive ( See Top 100 in Automotive ) #262 in Automotive Oils
Brand	Red Line
Customer Reviews	4.8 4.8 out of 5 stars (937)
Date First Available	12 August 2012
Exterior	Painted
Item Weight	771 g
Item model number	58204
Manufacturer	Red Line
Manufacturer Part Number	57-6525
Model	Red Line 57-6525
OEM Part Number	58204
Product Dimensions	22.86 x 9.88 x 9.83 cm; 771.11 g
Viscosity	75W90

Reviews

D**O

This is very good for Harley transmissions. Shifts smooth. Easy to find neutral.

3.01.2026

N**C

Questo olio per differenziale è veramente fantastico e mantiene ciò che promette. E' bene ricordare che è un olio per differenziale e non va usato nei cambi con sincronizzatori. Leggere le indicazioni di utilizzo e la scheda tecnica, sono chiare e ben fatte.

6.06.2021

3**0

My 3rd gear synchro was failing and grabbing and gridning getting in to gear, after a bit of reading I decided to try this and it fixed my gearbox and saved me $1000s.

7.03.2020

P**L

The best lube for Harley-Davidson Transmissions , quiets shift & makes finding neutral effortless!

28.10.2023

J**P

Don't trust anything better since its made for racecar transmissions. I have used in my Harley FXSTC transmission for 10 years and its at 77000 miles and still smooth and quiet.

3.03.2026

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