40 Gallon Tank

[Faster57]

I finally got started with the installation of the 40 gal. tank to replace the 21 gal. one that came from the factory. I ordered a tank,straps & sending unit for a 1974 suburban from Tanks to Pans. The depth and width of the new tank is the same as the old 21 gal. My '71 is a 3/4 ton 2wd with coil springs. The frame crossmember tha the panhard bar attaches to is installed in the frame at a angle so any measuring is done from the side rails and the rear crossmember. After you have the old tank out you have to remove the second from the rear frame crossmember, also the floor reinf. that lines up with the fuel filler. The new tank filler hits the reinf.

[Faster57]

The second step is to make two wood spacers to space the tank the correct distance from the rear floor. I trimmed a couple pieces of 4X4 treated. The front one is cut to fit between the small indent in the front top of the tank. with these blocks inplace on top of the tank and the tank jacked up into place you can install screws into the blocks from the top down from inside the rear of the suburban. this will locate the tank and hold it down from the floor. The tank looks low in the pictures but it is only 1" lower than the old tank. This weekend I will mount the straps and post the pictures on Monday. I will put the floor reinf. back in about 3 inches rearward of the original position, add a piece of flat stock to the top of the frame where the crossmember use to be then when I make the reciever hitch it will tie the bottom of the frame together.

[bad_turbo]

should this be a sticky???

[Faster57]

Here are the pictures of the front strap mounting ,a couple shots of the rear brackets and a pic. with the mounts all in place and the floor brace moved back a couple inches. Hope this will help someone else that needs more than 21 gal. Dave

[71meangreenc10]

Did the brackets and straps come with the tank? How is the filler neck going?

Smitty

[Faster57]

The straps are for the '74 tank. I just drilled holes in the crossmemer in front of the tank to mount it then bent up flat 3" wide strap metal to shape then welded sides on them for reinf. See the last 3 pictures in the last post. Dave

[Faster57]

I forgot to mention the filler. I don't expect any trouble with it. The new tank has the same Dia. filler as the old tank and is only a couple inches different in location so I will just get a longer hose to connect it. Also the vent will be routed to the sending unit with a longer hose. It also is the same Dia. I will extend the fuel line and block the extra vent in the sending unit and it should be good to go.

[71meangreenc10]

what sending unit are you using? Make sure you vent the tank to the filler neck or you may have alot of back pressure when you fill it up. looks like it fits well between the frame rails.

Smitty

[Faster57]

The sending unit is also from a '74 and it has the vent built into it instead of in the tank by the filler connection. Just use a longer hose from the neck vent tube to the sending unit vent. The only thing I'm not sure about is the sending unit wiring. It looks like the wire that you connect to the truck harness has a resistor in it. If when I test it before I install the last time I might have to splice a different wire W/O the resistor. I will let you know how it goes.

[71meangreenc10]

Do you know what the resistance is on the 74 unit? If I recall our trucks use the 90 ohm sending unit. I think it was changed to a 30 ohm sending unit later.

Smitty

[Faster57]

I don't know. I'm not a wiring expert by any stanard! I am guessing that by hooking up the ground and hooking the wire on the new sending unit to the harness it should work . If not then maybe the resistor is built into our harness and then just lose the resistor on the sending unit and try ir again? I'm open to any insight someone else might have.

[71meangreenc10]

Take a multimeter and check the new sending unit for ohms, run the black to the top of the sending unit and the red to the terminal, with the unit in the full position it should read low ohms with it in the empty position it should read high (either or) the only resistor is on the back of the gauge, if the new one reads 30 ohms then you will have to change the resistor on the guage to get it to work. I havent seen any resistors in the wires. I am going with after market guages so it wont matter which unit it comes with. The tank looks good and thats what I am going to do to mine.

Smitty

[4x4Poet]

I think the filler neck location on the '74 tank may prove troublesome. Looking forward to being corrected by pics.

[Faster57]

4x4, What do you see as the problem? Maybe I'm missing something and you could save me some time.

[454_72_4X4]

This is goin in a surburban, correct? I have no experience with Sub's but trucks, (my 72 for example), the sending unit wire is a resistor wire itself.

[Faster57]

From looking at the sending unit the resistor looks like I can remove it and connect directly to the exsisting wire. I'll just have to tyr a couple ways and see what it takes. Dave

[Faster57]

I checked the sending units with a multimeter and the ohms read the same when I move the float from empty to full so it should work. I am going to try to install the tank for the final time either Thursday or on Saturday. I need to extend the fuel line and hose's for the filler and the filler vent. Dave

[Faster57]

I finished up the tankand have some final pictures. I have one of the tank with the vent hose and the gas line hose and the other two plugged. I also took a couple of extending the fuel line and finally one of the filler neck hooked up. The only problem I ran into was that I had to cut and rotate the filler neck to line up with the tank then welded the tube back up with a wire feed.

[ranger danger]

Just what I was looking for!!

[Average Joe]

Sub'd for future reference as well. Seems like a good candidate for the FAQ section.