'72 K10 4WD Build

[ImAnIdiot]

So I am starting this thread to get some advice as I use these forums all the time to get info about my build. And I know less about rebuilding a truck than anybody in the world.

I bought this truck about a year ago and have done several things to it. The first picture is what it looked like when I bought it. It is a '72 K10 4WD. It had a rebuildt 305 from an 83 Monte Carlo when I bought it. Its no 350 but it runs strong, though it is geared way to low. The body was in shambles, as you can see, and I have spent the better part of 8 months doing body work by trial and error, mostly error. I will post some pictures of what it looks like now soon, and I just ordered two reproduction doors and a tailgate, and will likely need information on how to replace doors. I also completely redid the interior, including new gas tank, carpet, seats from an 88 Suburban, dashboard, head lining... all of it.

As the motor is strong and the interior is immaculate, my focus is on body work and then some suspension work. It needs bushings and body mounts and anything plastic or rubber... thats all shot.

There is some rust on the body (not much) and some rust on the frame. I dont have the time, money, tools, or knowhow to do a body off on this thing, so I will need some ideas on how to fix some of the frame rust without a huge rebuild. I am not looking for a show truck here, just a clean, safe, dependable driver.

I will be mosting many more pics about my progress so far very soon, and would appreciate any comments, suggestions, and even artistic ideas for this project. I am new to this and as I said, I dont know what the hell I am doing, so anything will help.

Jake

[ImAnIdiot]

This is the completed interior... well sort of, I have to re do all of the door trim and such when my new doors come in. Seats are electric seats from an 88 suburban.

[69gmcc10]

Your project looks great! I like your interior, have you checked for rust in the forward cap corners under the carpet? I only ask because my truck fooled me there. What transmission do you have? A 700r4 could make a big difference in gearing and you can pick up a used one for cheap if you know where to look.

[ImAnIdiot]

Thanks! Yes the whole cab is rust free. The floor panel was replaced before I bought it, and I am in the process of taking care of the exterior rust beneath the doors. The only real issue of rust on this thing is on the rear cab floor support. I know I can replace the whole support, I am just not sure if I will have to pull the cab to do it.

To be honest, I am not 100 percent sure what transmission is in this thing. I think the truck came stock with the 307 and the Muncie 4 speed manual. I know the motor has been replaced with a 305 from an 83 Monte Carlo (why.. I will never understand), but I dont know if that bolted up to the stock Muncie 4 speed (or whatever it is). I would love to replace the transmission (and engine really but I dont know if I can throw that kind of money at this). Does a 700r4 have an OD or just taller gears? Will it bolt up to the block of a 305? I think I am rolling with the 4.52 (or whatever they were) rear end, which is WAY too low. Thanks for the info.

[69gmcc10]

You are so lucky to have a rust free cab, enjoy not working on that! The 700r4 is a 4 speed auto that has an overdrive lock up, that drops the rpms @ cruse spee about 300rpms. It will bolt right up to any gm v8 and will require a wiring kit to manage the lock up feature, tci, bow tie transmission, and painless all make good kits ($50-200 based on features). It has a lower first gear for better acceleration and a higher final gear that is 30% higer for crusin speeds. I found my 700 on craigs list for $150 with 30k on the rebuild. If you like the manual trans you could always go to a t5 or a t56 manual, who doesn't like 5 and 6 speed transmissions!

[ImAnIdiot]

Yeah it is nice to have a rust free cab! Yeah I think I want to stick with the manual transmission. I dont want to mess with the steering column and holes in the floor and such. Do you think a different trans is the way to go to drop the rpms, or would a gear swap be feasible? Seems like a transmission would be an easier swap. Thats a good 69 project you have going too!

[69gmcc10]

To find what gear ratio that was originally in your truck there is a number stamped on the passenger side axle tube that can be cross referanced, I would find that numer and look on this site to find the ratio. The final drive grear on the muncie 4 is a 1.00 on the t5 and most t56 transmissions it is .62. That is a 38% reduction in rpms in the final drive gear not to mention it is a 15% lower first gear in the t5.

I cant see your tire size but I am going to assume they are 245 75 15 to give you something to think about. If we accept that you have 4.56 rear gears currently and you drive down the road at 70 mph your engine is turning at 3600 rpms, with a t5 transmission you will turn 2300 rpms. 1300 rpms, that is a big increase in efficiency! If you go a step further and change your rear gear to a 3.73 the rpms drop to 1850!

I dont know how easy or how expencive a t56 (6 speed in camaros and corvettes) would be but the t5 (in most manual v8s from 83-92) should be avalable in a salvage yard or craigslist near you for a reasonable price.

[ImAnIdiot]

I would bet money that they are 4.56 gears now. I jacked up the rear, marked the drive shaft and the tires, and I calc'd it to be somewhere around 4.50's. Thats awesome information man, I am going to look into a T5.

[69gmcc10]

What size of tire do you plan on running? Are you going to be running large tires? Do you plan on towing with this truck, off roading, daily driving or making a show truck?

I ask because your first gear ratio at the wheels now is 11.5:1 and with a t5 trans first gear will be 13.45:1, much much lower (You could drive it up a tree!). That is good if you have big tires, towe allot or want to off raod, but for a daily driver you wont need that low of a ratio. If you change the ring and pinion to 3.73 your first gear with the t5 is 11.05:1 and you are real close to the original 11.5:1 ratio you currently have, you also get allot more high end range. There is also the 4.11 r&p option to be somewhere in between.

If you change transmissions you may want to "eventually" change the ring and pinion as well.

[ImAnIdiot]

I plan on keeping the tires small, about the same as what is on it now. I wont be towing anything with it (I have a 96 GMC with a 454 for that), I wont be off roading, I basically want a driver.
After some thought, I think the best way to go about it is to change the ring and pinion to a 3.73 first. That will give me alot lower rmp's and I may even be able to use 1st gear again! If that proves to not be enough, then maybe I will think about a transmission swap. Basically, I just want to lower the revs and not feel like I am going to blow my motor doing 70 down the highway.

[69gmcc10]

I dont think you could go wrong either way, but i eventually would do both.

[ImAnIdiot]

Beat up old tailgate... Finally took this piece of junk off..

[ImAnIdiot]

New tailgate.. These reproduction parts are perfect! In the process of swapping the hardware now. Should have it on by tonight.

[ImAnIdiot]

Got my tailgaite on and got my doors delivered today. Pulled off one door and started trying to learn how to pull all the hardware off and out of a door. Does anyone know if the window seals can be salvaged and reused?

[ImAnIdiot]

I hope I dont break the window in the process