Fan and fan clutch - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Tully · 01-16-2005, 10:22 PM

I have a 71 GMC 3/4 ton 4X4 I want to change the stock 4 blade fan for a 7 blade with a clutch. Can some one tell me which model and year vehicles have a set up that will work on my truck. I plan to go to a junk yard to get it. Thanks in advance.

**kwmech** · 01-16-2005, 10:26 PM

Suburban big blocks in the 87-91 range

Tully · 01-16-2005, 11:34 PM

Thank's kwmech, is that all my choices? I read somewhere a 71 monte carlo will work or is that bad info?

Longhorn Man · 01-17-2005, 01:32 AM

Tully, welcome to the board..where do you call home?
Some of this will depend on what style pump you have. The bolt patern on short pumps (stock on these trucks) was not the same as the long pumps. However, many replacement pumps will have both bolt paterns on the hub so they can use the same part on either pump.
If you have a short pump, and it has the single bolt patern, then you'll be stuck with getting the part off a 69 or older car, or 72 and older truck...problem is, not many of either were sold with fan clutches. So this means parts store, and you'll pay through the nose from what I understand.
If you have a long pump, or a dual pattern hub, then you can grab the fan/clutch off of any GM rear wheel drive vehicle up untill the serp belt came in to play, which would have a reverse rotation pump, so that fan would blow air through the rad instead of sucking the cool outside air.

Tully · 01-17-2005, 09:27 AM

Thanks longhorn man. Home is in NE WI

Tully · 01-17-2005, 10:02 AM

I was a little slow digesting the info from longhorn man. Will the difference between the short and long style water pumps be enough to mess with the fan being half in the shroud? Also while on this subject what's the difference between 2 and 4 wheel drive setups, with the shrouds being twice as deep on the 4X4's.

Longhorn Man · 01-17-2005, 10:10 PM

4X4 trucks had the engine set back a few extra inches. This is the same location that the inline engines were installed too...but that doesn't matter for this conversation.
If a long pump is installed on an otherwise stockl truck, then the fan will be in the shroud about 2 inches further than needed.

**kwmech** · 01-17-2005, 10:23 PM

There may be more , but I know that the Suburban is a definate shoe in for a 7 blade.

4x4Poet · 01-17-2005, 11:00 PM

NAPA had US made fan clutches for my 71 for $30-$35. I can't remember, exactly. The seven blade fan costs $100 at the dealer! Same with Classic Industries.

Tully · 01-18-2005, 01:55 PM

Thanks a lot guys, thats just what I needed to know!

01-16-2005, 10:22 PM	#1
Tully Registered User Join Date: Jan 2005 Location: Hiles, WI Posts: 42	Fan and fan clutch I have a 71 GMC 3/4 ton 4X4 I want to change the stock 4 blade fan for a 7 blade with a clutch. Can some one tell me which model and year vehicles have a set up that will work on my truck. I plan to go to a junk yard to get it. Thanks in advance.

01-17-2005, 11:00 PM	#9
4x4Poet Registered User Join Date: Nov 2004 Location: "Under Montana skies." Posts: 1,836	NAPA had US made fan clutches for my 71 for $30-$35. I can't remember, exactly. The seven blade fan costs $100 at the dealer! Same with Classic Industries. __________________ '71 GMC K20 Suburban, '71 GMC K10 Suburban, '72 Chevy C10 CST Suburban, '72 Chevy K20 clunker pickup.

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01-16-2005, 10:26 PM	#2
kwmech Senior Member Join Date: Mar 2003 Location: Colfax-California Posts: 8,500	Suburban big blocks in the 87-91 range

01-16-2005, 11:34 PM	#3
Tully Registered User Join Date: Jan 2005 Location: Hiles, WI Posts: 42	Thank's kwmech, is that all my choices? I read somewhere a 71 monte carlo will work or is that bad info?

01-17-2005, 01:32 AM	#4
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	Tully, welcome to the board..where do you call home? Some of this will depend on what style pump you have. The bolt patern on short pumps (stock on these trucks) was not the same as the long pumps. However, many replacement pumps will have both bolt paterns on the hub so they can use the same part on either pump. If you have a short pump, and it has the single bolt patern, then you'll be stuck with getting the part off a 69 or older car, or 72 and older truck...problem is, not many of either were sold with fan clutches. So this means parts store, and you'll pay through the nose from what I understand. If you have a long pump, or a dual pattern hub, then you can grab the fan/clutch off of any GM rear wheel drive vehicle up untill the serp belt came in to play, which would have a reverse rotation pump, so that fan would blow air through the rad instead of sucking the cool outside air.

01-17-2005, 09:27 AM	#5
Tully Registered User Join Date: Jan 2005 Location: Hiles, WI Posts: 42	Thanks longhorn man. Home is in NE WI

01-17-2005, 10:02 AM	#6
Tully Registered User Join Date: Jan 2005 Location: Hiles, WI Posts: 42	I was a little slow digesting the info from longhorn man. Will the difference between the short and long style water pumps be enough to mess with the fan being half in the shroud? Also while on this subject what's the difference between 2 and 4 wheel drive setups, with the shrouds being twice as deep on the 4X4's.

01-17-2005, 10:10 PM	#7
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	4X4 trucks had the engine set back a few extra inches. This is the same location that the inline engines were installed too...but that doesn't matter for this conversation. If a long pump is installed on an otherwise stockl truck, then the fan will be in the shroud about 2 inches further than needed.

01-17-2005, 10:23 PM	#8
kwmech Senior Member Join Date: Mar 2003 Location: Colfax-California Posts: 8,500	There may be more , but I know that the Suburban is a definate shoe in for a 7 blade.

01-18-2005, 01:55 PM	#10
Tully Registered User Join Date: Jan 2005 Location: Hiles, WI Posts: 42	Thanks a lot guys, thats just what I needed to know!



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