The 1947 - Present Chevrolet & GMC Truck Message Board Network - View Single Post - DOT 4 fluid for clutch- why?

**hatzie** · 09-10-2023, 05:06 PM

DOT3 & DOT4 are both glycol based brake fluids. DOT4 has a significantly higher dry and wet boiling point. I'm not sure why they would use it in the clutch and not in the brakes from the factory. Good possibility someone changed the clutch master cylinder reserviour cap.

DOT4 is downward compatible so you don't have to clean the system entirely to update to DOT4. I run DOT4 in everything. An extra couple hundred degrees boiling point is a good thing when towing.

I changed the brakes on my 05 Silverado and my 09 Impala over to DOT4 when I flushed the brakes several years ago. I replaced the DOT3 master cylinder cap with the 92457850 DOT4 MC cap.
This is the post on flushing the brakes in my build thread. http://67-72chevytrucks.com/vboard/s...8&postcount=68

09-10-2023, 05:06 PM	#2
hatzie Moderator Join Date: Oct 2008 Location: Wentworth, NH Posts: 4,920	Re: DOT 4 fluid for clutch- why? DOT3 & DOT4 are both glycol based brake fluids. DOT4 has a significantly higher dry and wet boiling point. I'm not sure why they would use it in the clutch and not in the brakes from the factory. Good possibility someone changed the clutch master cylinder reserviour cap. DOT4 is downward compatible so you don't have to clean the system entirely to update to DOT4. I run DOT4 in everything. An extra couple hundred degrees boiling point is a good thing when towing. I changed the brakes on my 05 Silverado and my 09 Impala over to DOT4 when I flushed the brakes several years ago. I replaced the DOT3 master cylinder cap with the 92457850 DOT4 MC cap. This is the post on flushing the brakes in my build thread. http://67-72chevytrucks.com/vboard/s...8&postcount=68 __________________ 1959 M35A2 LDT465-1D SOLD 1967 Dodge W200 B383, NP420/NP201 SOLD 1969 Dodge Polara 500 B383, A833 SOLD 1972 Ford F250 FE390, NP435/NP205 SOLD 1976 Chevy K20, 6.5L, NV4500/NP208 SOLD 1986 M1008 CUCV SOLD 2000 GMC C2500, TD6.5L, NV4500 2005 Chevy Silverado LS 2500HD 6.0L 4L80E/NP263 2009 Impala SS LS4 V8 RTFM... GM Parts Books, GM Schematics, GM service manuals, and GM training materials... 1973-1991 GM Light Truck Service, Unit/Overhaul, Wiring Manuals, Parts Books and Some 1968-1999 GM Service Training textbooks in PDF 1988-1998 GMT400 CK service manual project 1988-1993 GMT400 CK parts books. 1967-1972 GM Light, Medium, & Heavy Truck Service Manuals in PDF Please include at least the year and model in your threads. It'll be easier to answer your questions. And please let us know if and how your repairs were successful. Last edited by hatzie; 09-10-2023 at 05:17 PM.