Fan clutch - Please Help!

[midnightrider78]

I have a 1972 C20 2wd Custom Camper 402, Auto, A/C that I am trying to get a thermal fan clutch for. The one I have and that everyone lists(Murray 2707, same # as Hayden and Parts Master) is absolutely not correct. The clutch is larger in diameter and appears lighter duty than the old one. The biggest problem is the fan mount height. The 2707 is just a hair over 2" and puts the fan much closer to the radiator. The one that came off the truck is 1 9/32".

So what gives?

I need my truck back on the road and I hate to use the old fan clutch. There is not a lot of wobble, but I figure virtually any is too much since I just replaced the water pump on Friday.

[randy500]

You could try contacting our member PICKMUP, his name is Frank Ham
Google this for his phone number,

Frank's Pickmups Truck Parts Oly, wa

he has a lot of fan clutches.

[Stocker]

Yup, that #2707 is shown as just over 2". I would say you need a Hayden #2747, but its mounting height is 1 5/8" so maybe a bit more than you're looking for. You probably already know that you need a Heavy Duty unit.... Hayden's site shows the differences http://www.haydenauto.com/featured%2...s/content.aspx.

[midnightrider78]

Originally Posted by Stocker

Yup, that #2707 is shown as just over 2". I would say you need a Hayden #2747, but its mounting height is 1 5/8" so maybe a bit more than you're looking for. You probably already know that you need a Heavy Duty unit.... Hayden's site shows the differences http://www.haydenauto.com/featured%2...s/content.aspx.

I don't know if it will make a difference, but #2747 has a slightly different mount diameter and pilot depth.

[davepl]

FWIW, this is the unit I bought and am running with good success on my '70 402:

https://smile.amazon.com/ACDelco-15-...words=15-80250

It says that's not correct, and they list this one as fitting, but I have the one above.

https://smile.amazon.com/Flex-a-lite...2Fc2500+pickup

[midnightrider78]

Originally Posted by davepl

FWIW, this is the unit I bought and am running with good success on my '70 402:

https://smile.amazon.com/ACDelco-15-...words=15-80250

It says that's not correct, and they list this one as fitting, but I have the one above.

https://smile.amazon.com/Flex-a-lite...2Fc2500+pickup

Wonder what is different about mine? The Ac Delco you show is a direct interchange with the 2707 they sold me. Do you have a fan shroud and stock radiator on your truck? Besides the 2707 putting the fan blade too far inside the fan shroud on my truck. I also cannot fit the clutch and fan blade in if I bolt them together first(they won't clear as an assembly, they want to dig into the radiator getting them in place).

[Stocker]

Originally Posted by davepl

FWIW, this is the unit I bought and am running with good success on my '70 402:

https://smile.amazon.com/ACDelco-15-...words=15-80250

It says that's not correct, and they list this one as fitting, but I have the one above.

https://smile.amazon.com/Flex-a-lite...2Fc2500+pickup

Near as I can tell, both of those are standard-duty units. From what I have read, an A/C truck should have a heavy-duty (my K20 had a HD on it from the factory). The Hayden link I posted above explains the differences. Standard-duty has a smooth steel faceplate, and heavy-duty has a finned aluminum faceplate. OP, you could try contacting Four Seasons in Lewisville, Texas for correct fitment info. That's the company that manufactured the one I bought last year to replace my leaking OEM unit.

[midnightrider78]

Originally Posted by Stocker

Near as I can tell, both of those are standard-duty units. From what I have read, an A/C truck should have a heavy-duty (my K20 had a HD on it from the factory). The Hayden link I posted above explains the differences. Standard-duty has a smooth steel faceplate, and heavy-duty has a finned aluminum faceplate. OP, you could try contacting Four Seasons in Lewisville, Texas for correct fitment info. That's the company that manufactured the one I bought last year to replace my leaking OEM unit.

I actually called Four Seasons right before I posted today. They weren't much help. They suggested a severe duty one with 1 5/8" fan mount height(which I just happen to have in all my extra parts), but my fan blade didn't have quite enough pitch to use that one.
It seems there is nothing available anywhere that is actually a match to the old fan clutch.
I looked at the Hayden web site some more and narrowed it down to 2747 or the 2705. The 2747 that you had suggested is the closest heavy duty one. The 2705 is actually a little closer yet(1 1/2" fan mount height), but is only standard duty.
I ended up ordering the 2747 and it's supposed to be here in the morning.

[Steeveedee]

I'm following this with interest, because I think I may have the same 2" high clutch, since I can't get the fan belts off unless I remove the fan. I'll have to look into that.

[Stocker]

Hope it fits the way you want it to. I got my 2747 (for my '72 K20) at my local NAPA store, but it wasn't easy. After a few failed attempts involving their recommended light-duty units, we finally got one for a mid-seventies K30, which is a HD unit. It's a perfect fit on my truck.

[midnightrider78]

Been driving the truck the last couple days. So far so good. I believe the 2747 is a winner.

[Stocker]

Excellent, glad to hear it -- thanks for the follow-up!

[davepl]

Does anyone know what the functional differences are? I'd assume the amount of slip vs heat varies, but don't actually know.

[Steeveedee]

Originally Posted by davepl

Does anyone know what the functional differences are? I'd assume the amount of slip vs heat varies, but don't actually know.

I'd be interested in knowing what the fan-to-radiator clearance is. As I mentioned previously, I had a tough time changing belts because of fan-to-radiator clearance. I bought the current clutch a few years ago, and it may well be that it is the wrong one, based on what I'm seeing here. Maybe we should make a library of what part numbers work for what year truck, because we have to rely on people who are young enough to be our grandchildren to look up parts for us, when we go to the parts store. Though for what is worth, one parts store I used to go to has a guy about my age that isn't sure which way is up, most of the time.

[midnightrider78]

Originally Posted by Steeveedee

I'd be interested in knowing what the fan-to-radiator clearance is. As I mentioned previously, I had a tough time changing belts because of fan-to-radiator clearance. I bought the current clutch a few years ago, and it may well be that it is the wrong one, based on what I'm seeing here. Maybe we should make a library of what part numbers work for what year truck, because we have to rely on people who are young enough to be our grandchildren to look up parts for us, when we go to the parts store. Though for what is worth, one parts store I used to go to has a guy about my age that isn't sure which way is up, most of the time.

Just measured mine with the 2747. There is about 2 1/4" between the fan blade and the radiator.

[midnightrider78]

Originally Posted by davepl

Does anyone know what the functional differences are? I'd assume the amount of slip vs heat varies, but don't actually know.

I'm pretty sure the difference is the speed the fan is moving vs the water pump. I think I read somewhere that a standard fan clutch is moving at 70% of the drive(water pump) speed when its engaged and a heavy duty is 85%.

[Steeveedee]

I just went out and measured mine. The front edge of the fan blades are about one inch from the radiator. That probably explains why the thing roars all the time, too. Looks like I have a fan clutch replacement in my near future.

[Stocker]

Originally Posted by midnightrider78

I'm pretty sure the difference is the speed the fan is moving vs the water pump. I think I read somewhere that a standard fan clutch is moving at 70% of the drive(water pump) speed when its engaged and a heavy duty is 85%.

Per Hayden's website:

Standard Duty turns fan at 60-70% of shaft speed when engaged

Heavy Duty turns fan at 70-90% of shaft speed when engaged

Severe Duty turns fan at 80-90% of shaft speed when engaged