New to me 71 GMC, a few questions

[Christiansok]

I've been lurking these forums for awhile but just last sunday I bought a 71 GMC for my daily driver and it has a few quirks that I hope the experts here can help me straighten out.

First off some details:

1971 GMC 4x4 LWB
350ci V8, TH350
3-4"? home made body lift
31x10.5" tires

First thing to raise some questions was the VIN. It starts with a 'C' but the truck is 4 wheel drive. So I assume a previous owner swapped a cab off a 2 wheel drive. The thing I couldn't figure out though, in the digit where the year usually is it has '-' instead of any number 7, 8, 9, 0, 1 or 2.

The second thing that I'm unsure of is the tranny dipstick. The stick is brand new but when I checked the fluid level after driving it 2 hours home (with no problems) there isn't a drop of fluid on it. The stick is about 34.25" long and from eyeballing the tube I think its too short. How long should it be?

Third, are the front leaf springs on the 4x4 models originally flat? I was expecting them to have some upward arch but mine have a slight downward arch. I was wondering if they were flat originally and sagged down over time.

Fourth, my fuel gauge always reads empty. Is the wire running to the sending unit on the tank the ground or power? I cleaned up the wire/connection on the outside thinking it was the ground. Unplugging this wire from the fuse panel under the dash buried the needle on the fuel gauge so the gauge itself works. What is my next step? I'm thinking either the float doesn't float inside the tank or there's a short in the ground. Where is the ground for the sending unit located?

Lastly with the body lift in place the mechanical fan doesn't line up very well with the radiator causing it to run hot idling. I've read a few electric fan swaps (jeep fans, lincoln fans, etc) but has anyone used the 16" electric fan kit from LMC (or a similar all inclusive kit)? I've never done an electric fan upgrade so I was thinking a kit would be the best way to go so there's less chance of me screwing it up.

Also, are there any small upgrades I should consider that are done to these style trucks by expierenced people? What I mean are upgrades specific to this style truck that among people familiar with them are pretty much common knowledge (i.e. something about getting a 4-4.5" tall air filter?).

Anywho...appreciate any help/experience you guys can share.

[GruntMoanCough]

Congrats on your purchase and Welcome! Pics are required, you know .
I'm thinking maybe a 4x4 conversion, what does the registration say?

[gregg72340]

Welcome to the board always nice to see another 4 eyed guy on here. Make sure on the Vin decoder that you are looking at the GMC decoder, because I had the same problem but I was looking at the Chevy decoder

Post some pics of the new truck

[Christiansok]

I suppose a teaser pic is in order, took this with my phone stopping for gas before I drove it home. Maybe its just me but the front axle does seem shifted backwards off center in the wheel well so maybe a 4x4 conversion is what happened??

[71GMC71]

How did you put that hood on there? Thats a older hood.

[Christiansok]

How did you put that hood on there? Thats a older hood.

No idea, that's just how I bought it. Seems to work fine but the gap towards the cowl is a bit big and its a bit tall compared to the front fenders right about the center of the wheel well.

[GruntMoanCough]

Looks as though the "Chevy" fenders have been modified to fit the hood.

Edit: Actually, something doesn't look right with the fenders.

[Christiansok]

Here's some more pictures of the hood/front clip that may help clear things up





And here is a side shot where the front axle positioning looks kind of off to me (shifted too far back)

[gregg72340]

Originally Posted by GruntMoanCough

Looks as though the "Chevy" fenders have been modified to fit the hood.

Edit: Actually, something doesn't look right with the fenders.

IMO I think its an illusion because the fenders dont have the eybrow mouldings on them but the hood does. The hood definitly needs to be moved back, but I dont think they're Chevy Fenders because the grill is sitting flush like it should, I think with the other fenders it wouldnt fit right

[gregg72340]

Originally Posted by Christiansok

Here's some more pictures of the hood/front clip that may help clear things up





And here is a side shot where the front axle positioning looks kind of off to me (shifted too far back)

It seems like you might have the same problem with the rear axle too if you look at your last picture, I dont know just a thought is there any adjustment in the bodies on these trucks that you could basically move the body back an inch or two to fix it

[too much stuff]

Decent looking truck. I would check numbers, VIN glovebox door, etc to make sure of what it is. It looks like a 67 cab, 67 box, 68 hood, 69 and newer fenders.
The leafs i wouldn't worry about. They are usually flat or arched the wrong way after this many years.

[raycow]

Originally Posted by Christiansok

Fourth, my fuel gauge always reads empty. Is the wire running to the sending unit on the tank the ground or power? I cleaned up the wire/connection on the outside thinking it was the ground. Unplugging this wire from the fuse panel under the dash buried the needle on the fuel gauge so the gauge itself works. What is my next step? I'm thinking either the float doesn't float inside the tank or there's a short in the ground. Where is the ground for the sending unit located?.

Power goes from the ignition swtch to the dash gauge to the tank sending unit. The tank sending unit is grounded through the tank mounting to the body. If the dash gauge reads empty when the sending unit lead is connected and full when disconnected, the dash gauge, wiring, and sending unit ground are good. You likely have something binding the float arm or a leaky float that's filled up with gas. The only way to find out is to pull the sending unit out of the tank.

Ray

[Christiansok]

Thanks Ray, I'll pull the sending unit out next and check the float.

I was looking around for some VIN info for GMCs and found this:

http://outintheshop.com/vin_decode.html

So it turns out the GMC VINs are only 12 digits with a hyphen?

According to that website I have,
4x2, V8, 1/2 ton, Fleetside, Jainesville, 1971

My model number (if its the same chevy/gmc) on my glove box door, CS10934 tells me that its a 4x2, inline 6, 1/2 ton, fleetside....so thats even more confusing...

On the line right under the Model number I can make out 292...is the line below the model number related to the engine? Would make sense if the model number says it has a straight 6 then below it says 292...but that just confuses me more because the model number/VIN conflict with each other.

[Dazed and confused89]

I have a 1969 Gmc 2wd and i say the the earlier model hood looks smoother than the later ones with the squared off face

[chisler]

Maybe its me but,the rear shocks are mounted(upper) on the outer frame rails which makes me think some has been changed.Usually they are mounted on the inside frame rail

[Christiansok]

Maybe the body was swapped onto a different frame? That could explain the front axle shifted back, the 4x4 conversion and the body lift. Any features to look for to identify the frame as a 71?

[Christiansok]

For those suggesting the front clip, cab and bed are 67-68 what do you look for to tell? The front of the hood has the laid back angle and the cab has the small rear window, do both of these signs point towards 67-68?

[gregg72340]

Originally Posted by Christiansok

For those suggesting the front clip, cab and bed are 67-68 what do you look for to tell? The front of the hood has the laid back angle and the cab has the small rear window, do both of these signs point towards 67-68?

You definitly have a 67/68 hood, no question, the fenders are 68-72 GMC, 67 parts would have no marker lights in them at the corners so from your pics it looks like your bed is a 67, either that or someone filled in the marker holes, and the small rear window is a 67 only deal, so you definitly have some mismatched parts on there......So it really makes you no difference than the rest of us LOL

[Christiansok]

Thanks for the help Gregg.

So shes a miss matched bag of parts, oh well haha
But this does raises some questions because the VIN plate on the cab is for a 71 but the cab is definetely a 67...so someone must have transplanted the VIN plate to the older cab? Is this acceptable?

[gregg72340]

Originally Posted by Christiansok

Thanks for the help Gregg.

So shes a miss matched bag of parts, oh well haha
But this does raises some questions because the VIN plate on the cab is for a 71 but the cab is definetely a 67...so someone must have transplanted the VIN plate to the older cab? Is this acceptable?

Yeah there are lots of reasons why this happens may have been wrecked and rebuilt, or the cab rotted out and was replaced, or they lost a title and had a good vin with a plate and swapped them etc....etc....etc....Check on the frame somewhere near the steering box there should be a partial vin to see what it really may be, it may actually be a 71 with metal parts replaced who knows. I am having the same problem with my truck I think its been replated at some point in its life but from what I can tell mine is definitly a 68 just the Vin number has been ground of the frame on mine. and to answer your last question I believe its illegal to swap the plates from vehicle to vehicle but like everything else in life.....It does get done. Will be interested to see when you finally figure out what she really is ........Good Luck
Gregg

[Tim Christian]

Those are 68 GMC front fenders you are missing the 68 style eyebrowls