Which Hayden Fan Clutch for D2?

SafariDave

Well-known member
Callsign: Safari
Sep 14, 2008
88
0
Brooklyn, NYC
I want to replace the old fan clutch on my 1999 D2 SD. Which one is best Hayden Heavy Duty 2781 or Severe Duty 2991? I keep this D2 in the Caribbean hot weather all year.
Thanks,
Dave
 

bgbrox

Well-known member
Dec 25, 2016
50
3
Golden, CO
I have the 2991 is my D1. It's very loud, but it certainly moves air. If you're sensitive to fan noise, I bet the heavy duty is perfectly capable of doing what it's supposed to do.
 

bgbrox

Well-known member
Dec 25, 2016
50
3
Golden, CO
Why would the clutch be noisy? I can see another fan design being loud, but the clutch?
Not the clutch, but the resulting speed of the fan is louder. In the way that a desk fan moving from low, to med or high gets louder. As compared to my worn OE clutch and my brothers D1 with a different clutch, the 2991 is louder. Standing outside the truck while it's idling or from the seat while driving.
 

bgbrox

Well-known member
Dec 25, 2016
50
3
Golden, CO
Q. What is the difference between a standard, heavy and severe duty fan clutch?
A. Each fan clutch type is designed to simulate the performance of the original equipment clutch that it replaces. All fan clutches are for specific applications and should be applied only on the application for which they are cataloged.

Standard Duty Thermal
Turns the fan 50-60% of shaft speed when engaged. Used with fans with lighter pitch. (1-1/2" of pitch) Flat plate impeller design with 30 Sq. In. of working surface.
Heavy-Duty Thermal
Turns the fan 80-90% of the shaft speed when engaged for increased cooling. Used with deeper pitch fans. (2 1/2" of pitch). Land and groove design with 47 Sq. In. of working area allows higher operating RPM's.
Severe Duty Thermal
Turns the fan 80-90% of the shaft speed when engaged. Used with deeper pitch fans. (2- 1/2" of pitch). Land and groove design with 65 Sq. In. of working area. Larger working surface provides cooler running and longer life expectancy.
 
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SafariDave

Well-known member
Callsign: Safari
Sep 14, 2008
88
0
Brooklyn, NYC
Q. What is the difference between a standard, heavy and severe duty fan clutch?
A. Each fan clutch type is designed to simulate the performance of the original equipment clutch that it replaces. All fan clutches are for specific applications and should be applied only on the application for which they are cataloged.

Standard Duty Thermal
Turns the fan 50-60% of shaft speed when engaged. Used with fans with lighter pitch. (1-1/2" of pitch) Flat plate impeller design with 30 Sq. In. of working surface.
Heavy-Duty Thermal
Turns the fan 80-90% of the shaft speed when engaged for increased cooling. Used with deeper pitch fans. (2 1/2" of pitch). Land and groove design with 47 Sq. In. of working area allows higher operating RPM's.
Severe Duty Thermal
Turns the fan 80-90% of the shaft speed when engaged. Used with deeper pitch fans. (2- 1/2" of pitch). Land and groove design with 65 Sq. In. of working area. Larger working surface provides cooler running and longer life expectancy.
Thanks for your help!
So which clutch would be best for my D2 1999? The heavy duty or the Severe Duty? My truck is in the Caribbean so constant hot weather year round, slow driving roads with stop and go traffic and very long red lights. I don't know what fan the clutch has, but I believe its the one that came with the original D2 clutch which can be taken off. Will that fan be ok?
Thanks,
Dave
 

bgbrox

Well-known member
Dec 25, 2016
50
3
Golden, CO
Well, my Hayden pissed all it's oil all over the place and nearly overheated. 8 months and 2k miles. I officially retract my earlier recommendation. :censored:
 
Last edited:

JUKE179r

Well-known member
Sep 14, 2016
220
6
Suffolk, England
Thanks for your help!
So which clutch would be best for my D2 1999? The heavy duty or the Severe Duty? My truck is in the Caribbean so constant hot weather year round, slow driving roads with stop and go traffic and very long red lights. I don't know what fan the clutch has, but I believe its the one that came with the original D2 clutch which can be taken off. Will that fan be ok?
Thanks,
Dave
IMHO... Heavy Duty #2781. I'm sure you won't get crazy Kuwaiti temps (134 degrees) so you'll be alright with the HD.
As for the fan, check your fan to see if it is in good condition... no cuts/cracks on the fan blades or wobbles when it is turning.
When I decided to change out my fan clutch I also changed to a Dorman #620-112 fan (my stock fan had deep cuts in a few blades) and installed a 180 degree thermostat for my V8 4.0L.
Now... the next question is which type of thermostat do you have? Stock 190 degree or 180 degree?
 

SafariDave

Well-known member
Callsign: Safari
Sep 14, 2008
88
0
Brooklyn, NYC
IMHO... Heavy Duty #2781. I'm sure you won't get crazy Kuwaiti temps (134 degrees) so you'll be alright with the HD.
As for the fan, check your fan to see if it is in good condition... no cuts/cracks on the fan blades or wobbles when it is turning.
When I decided to change out my fan clutch I also changed to a Dorman #620-112 fan (my stock fan had deep cuts in a few blades) and installed a 180 degree thermostat for my V8 4.0L.
Now... the next question is which type of thermostat do you have? Stock 190 degree or 180 degree?
I have a 180F grey thermostat