New Purchase 1970 C10 - Questions

[rmawyer]

New owner 1970 C10 & new forum member:
VIN CE140B107056 4X2, V8, 1/2 ton, pickup/cab/bed, 1970, Baltimore
1. Original tires were 205 / 75 / 15 or 215 / 70 /15. Current tires are 235 / 75 /15 and they need to be replaced. Keep current size or get original? How can I determine which size was original?
2. Speedometer not accurate - shows 100 MPH when doing 50 or 60 MPH. Simple matter of replacing cable or does it need a recalibration if the tire size is not original?
3. No radio in dash but dash radio opening has been cut. Best place for original look radio and how to replace original opening?
4. Suspension worn - good place for parts?
5. Window rattling - good place for parts?

[hugger6933]

Welcome to the site you are welcome and will find lots of help here. With the speedo being that far off you either have a trans that has been replaced and had way wrong speedo gears or the rear end has been changed and that makes the speedo off. A tire change like your talking about would not put the speedo off by twice. So you will have to start from scratch, find out the rear gear ratio then find out witch gears are needed for the speedometer. You can find a chart somewhere on line telling what color gears you need for the speedometer to get it right.
Now on the radio there are dash cuts for sale in the parts section quite often to patch the hole in your dash.
As far as parts you will find great deals on E-bay I know lots of people frown on it but I buy parts there at great bits cheaper than the local parts stores. Jim

[rmawyer]

Jim - thanks for your insight. I didn't consider the rear change as a cause.

[mike16]

speedo could be off by a combination of wrong tire size and a replacement rear/tranny from another vehicle. choose your tire first befor correcting the speedo. I have 235's on my 72 and they look good , ride good and they have lasted 32k so far..

sort out your front end befor you drop any money on the tires

the radio deal; unless you want to repair the dash, aftermarket is the way to go but I would not cut the truck up further for speakers and stuff like that.

rattling windows are fun projects down the road

[LPoole]

Welcome to the site. You'll find all kinds of good advice on here. But... we like to see pix. lol

[gvw5400]

WELCOME , Lot's of good advice above. For what it's worth the original tire size was likely
a G-78-15 . Close in size to a 215-75 R 15 . That being said I would run the 235-75 R15 .
I like the way it helps fill the wheel well . All The Best , Dirk

[rmawyer]

Thanks for the feedback - pics attached.

[gvw5400]

Nice, I like the White-hugger-white combo. Thanks for the pics.
All The Best , Dirk

[Sleepy Cheyenne]

Welcome to the board. Speedo would be mainly different rim sizes.

[yuccales]

Good looking truck you got there.

[alsriv2]

Bought from Brown's in Glen Burnie I see.
Moved from there last year. Nice looking truck, as others have mentioned, take your time and move slow on making changes and such. Those rims on your truck come from a newer model year (I suspect) and pretty much require the 235 series tires, the 205's will be too narrow and more than likely were the tires installed on the trucks original rims.

I had a '67 GMC that had a few transmission changes when I owned it. Each transmission produced its own speedometer readings as I never changed the internal transmission speedo gears. I was told it was easy to do, but the transmission had to be disassembled to make the change. (Doesn't sound easy at all).

Good luck and enjoy those crabs!

[rmawyer]

Thanks for the comments. MD is home but SD is nice all year long. Any mechanic near Ellicott City you can recommend?

[70cst]

Hey rmawyer ...

to the forums and from Ohio.

on one 70 C10.

C10 rocks

[alsriv2]

Originally Posted by rmawyer

Thanks for the comments. MD is home but SD is nice all year long. Any mechanic near Ellicott City you can recommend?

Depends on what you are looking for specifically. I mostly did my own work, but I had CGM Motorsports in Millersville do a complete overhaul on my 396BB. They did fantastic work.

Kens transmissions (right near Brown's) seem to have the best reputation for transmission work, but I am sure there are plenty of good shops up in your area. Once you are able to figure out what gear ratio the truck has, you can go to a transmission place and they will be able to regear that speedo output for your setup. There are also adapter units available that mounts externally to the transmission that can perform the same function.