Making a mud toy

[1976Scottsdale]

I have my 79 k10 almost done now.  It has the factory 3.40 gears in it and it has 33's.  It is a 350 engine, turbo 350 trans, and an np203 t-case.  My dad wants to put a 5 speed in his truck and he has 4.56's in his truck.  He wants my 3.40's.  Should I trade him for his pair of 4.56 posi front and rear ends?  His truck is a 79 shortbed, mine is a 79 longbed, will everything swap?

[roundedline]

If both are 4x4's the axles will swap with no problems.  Should you is a question you will have to answer.  Do you like driving his?  

Chris Lucas
www.73-87chevytrucks.com
www.captkaoscustoms.com
Project Su
Jimmy 2WD Project

[1976Scottsdale]

I love driving his truck.  My only dislike about the whole thing is that his turbo 350 hits third gear before it reaches 30 miles an hour.  However, I am not building a cross country truck, though, I do know that with a rebuild 350, and a street avenger 770 carb, he was getting about 150-175 miles from his 16 gallon tank.  So, he got on average 10 miles per gallon.  I am running a 750 quadrajet for now and a rebuilt 350, so I hope to achieve about the same as his did.  I have a friend who I am helping to work on his 1980 sierra 15 4x4, he is about to destroy it, he was doing 80 on only his front end in 4 lo with his muncie m22 and an np205.  Now he has both drivlines back on and is running 4.56 rear gears and 4.11 front gears.  He will not have his truck for long I think.  Oh well, I plan to own it when he rids himself of it.  I will fix it how it should be fixed.

[captkaoscustoms]

If you swap to the 4.56 gears the shifting will be the same unless tire size is drastically different.
The 81 K10 I had with a crate motor and SM465 and 3.73 gears and 31" tall tires got 14mpg when I had it.  You should be able to get at least that from it.

Running that large a difference in ratios front to rear is not a good decision.  They should be no more than 1% variance for the street.

Chris Lucas
www.captkaoscustoms.com
www.73-87chevytrucks.com

[77DuallyCowboy]

Let me ask you this, What is your main use for this truck? mud im assuming, so YES id swap to the 4.56 posi's, the biggest difference is engine RPM, according to 700r4.com's calculator u will be running 2500 at 55 and 3 grand at 65 with the 33's n 4.56's. and probly 10 miles to the gallon     Like i said if this is a mud truck I would do it. Dont forget to get the right speedo gears, (if ya really care) Someone else would have to answer that one for ya, ive always delt with 2 wheel drives so i know all it is, is a gear in the trans. I just bought my first 4x4 last month (now i need an engine) And my speedo is off but thats another story. Hope that helps!

[1976Scottsdale]

I will be running 4.11's, that is what is in my dad's truck, not 4.56's, just found that out today.  I will use 4.11's front AND rear.  I know what happens when you do not use equal ratios.  I am also going to buy a kit for my speedo to make it be correct.  My local speedo cable shop sells a ratio adaptor that will make it work correctly.

[1976Scottsdale]

I got the truck running and driving on Sunday.  It still has no passenger floor or center hump, but it drives.  The 350 runs great, I can give it less than a quarter petal and darn near twist the frame 6 inches.  This is with the 750 quadrajet.  The quad is also my main mechanical issue.  The thing loads up really bad and lugs when you first get on it, then it takes off.  So, I will be installing a new Edelbrock Performer 600CFM manual choke carb.  Also, the dual exhaust kit that I got would not claer the torsional support from the transfer case to the NP203, so, I took off the support.  This has had no effect on how the thing performs.  Finally, when I put it in gear, the thing makes a rather interesting "TINK."  I know what that is too, the u-joints are bad, but those are easy.  For 200.00, I got a straight frame, np203, th350, posi front and rear diff's, new ball joints, all 4, and a rancho steering stabilizer.  I found out that the truck takes off way too fast to be 3.40 gears.  It flies forward and hit 30-35 in about 4 seconds.  I do not know what they are yet.

[k10caddy]

assuming you are completely correct, how did your firend mate up an m22 to a 205, or is it a divorced transfercase?  

[1976Scottsdale]

As it turns out, he thought he had installed a muncie, but he had actually installed a saganaw of some kind.  However, he does have a mated transfer case.  My NP203 works very well, so I will not do a swap from auto to manual right now.

[1976Scottsdale]

Alright, got the truck on the road and functioning well as a daily driver and snow toy.  I am now planning to replace the th350 rather than rebuild mine or convert to a 4 speed.  I can get an extreme 4x4/HD th350 for my truck with extra clutches, kevlar band, hardened races, and 36 element sprag drum, plus a shift kit for $550.00 delivered to my door.  I am going to do this, I think.  What I want to know is, what are some other upgrades I should consider over the winter that can be done one at a time and not take more than a weekend or two.  I have not lifted the truck other than a 2 inch body lift to clear my low hump and the transfer case.  The engine is a rebuilt 350(done by me).  It makes roughly 375-400hp and 425 torque.  It runs well in an automatic and does not slam into gear.