Sending unit question - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Will B · 07-11-2018, 07:33 AM

Is there a difference in sending units between a 16 gal and a 20 gal tank?

**mr48chev** · 07-11-2018, 09:25 AM

I've been looking for one for my 77 dualie and what I am seeing on Rock auto is 2 outlet or 3 outlet drivers side or passenger side.

If you click on the part number in blue it shows what it fits but doesn't distinguish between 16 and 20 gallon tanks https://www.rockauto.com/en/catalog/...ding+unit,4436

Checking the height and width where the sender sits they are the same on both tanks. Some sites say that the 16 gallon is a short box tank looking at the photos it looks like the added capacity is at the front of the tanks.

**Palf70Step** · 07-11-2018, 03:23 PM

They are the same for both size tanks. They differ on whether right or left side and 2 or 3 tube. I can't remember what year they went from 2 tube to 3 tube on the fillers, but I believe it was around 1978.

**hatzie** · 07-12-2018, 09:36 AM

The third tube is your return line. If you have a return line from the fuel pump you need all three.
Not sure exactly when the return line became standard equipment but I believe it was available in the early 70's...

I don't believe you can install 20 gallon tanks with a 6' box.

16 & 20 gallon pickup tanks are the same depth so they use the same supports and the same senders. Blazer and Suburban tanks have differing depths.

The senders are side specific but the supports are not.

07-11-2018, 07:33 AM	#1
Will B Registered User Join Date: Jan 2018 Location: S.E. IA Posts: 8	Sending unit question Is there a difference in sending units between a 16 gal and a 20 gal tank?

07-11-2018, 09:25 AM	#2
mr48chev Registered User Join Date: Jul 2007 Location: Toppenish, WA Posts: 15,735	Re: Sending unit question I've been looking for one for my 77 dualie and what I am seeing on Rock auto is 2 outlet or 3 outlet drivers side or passenger side. If you click on the part number in blue it shows what it fits but doesn't distinguish between 16 and 20 gallon tanks https://www.rockauto.com/en/catalog/...ding+unit,4436 Checking the height and width where the sender sits they are the same on both tanks. Some sites say that the 16 gallon is a short box tank looking at the photos it looks like the added capacity is at the front of the tanks. __________________ Founding member of the too many projects, too little time and money club. My ongoing truck projects: 48 Chev 3100 that will run a 292 Six. 71 GMC 2500 that is getting a Cad 500 transplant. 77 C 30 dualie, 454, 4 speed with a 10 foot flatbed and hoist. It does the heavy work and hauls the projects around. Last edited by mr48chev; 07-11-2018 at 09:40 AM.

07-11-2018, 03:23 PM	#3
Palf70Step State of Confusion! Join Date: Jul 2002 Location: Gulfport, MS USA Posts: 47,274	Re: Sending unit question They are the same for both size tanks. They differ on whether right or left side and 2 or 3 tube. I can't remember what year they went from 2 tube to 3 tube on the fillers, but I believe it was around 1978. __________________ Bill 1970 Chevy Custom/10 LWB Fleetside 2010 Toyota Tacoma PreRunner SR5 Double Cab - DD Member of Louisiana Classic Truck Club (LCTC) Bill's Gallery Life isn't tied with a bow, but it's still a gift. Live simply. Love generously. Care deeply. Speak kindly. Leave the rest to God!

07-12-2018, 09:36 AM	#4
hatzie Moderator Join Date: Oct 2008 Location: Wentworth, NH Posts: 5,014	Re: Sending unit question The third tube is your return line. If you have a return line from the fuel pump you need all three. Not sure exactly when the return line became standard equipment but I believe it was available in the early 70's... I don't believe you can install 20 gallon tanks with a 6' box. 16 & 20 gallon pickup tanks are the same depth so they use the same supports and the same senders. Blazer and Suburban tanks have differing depths. The senders are side specific but the supports are not. __________________ 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.



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