Gear Ratio? and a couple other questions.

[BloodMoon]

I probably missed it somewhere but here it goes...

I am need of a gear ratio recommendation for my build. Also, brand recommendations? Whats a decent price to have a shop install new gears?

I have a 383 going in by the end of this month.

The transmission is TH350, and transfer case is a NP203

It has 33" tires now, and pretty sure the current gears are 3.73

I really want to put some BFG AT 35s on it but don't want to damage anything.

I found some info and people were recommending 4.56 or 4.88 but I think their trucks had an overdrive?

What do you think would be best for my setup? A lot of daily driving and I do not want to tow it to the trail. I want to run the desert, trails, small rocks... The truck will do some towing.

On the subject of tires, I am unfortunately going to ask the question that has been asked before... many times...

I have just finished the bodywork and painted my truck and I am scared of the fender trimming/bending.
35" tires.. 4" lift.. (rims are 15x10, don't recall the backspacing) any idea how much "adjusting" I am going to need to make?

Or should I skip the plans and stick to 33" with 3.73...

Thank you all for your help!

 

[tRustyK5]

If you don't want to trim, stick with 33's. Wider rims with more backspace make the problem worse, so if you really want 35's keep stock width and backspace rims and you can get away with some really minimal trimming.

With the TH350 I'd keep those gears, especially if it sees any time on the highway. To run much deeper you need an overdrive tranny.

 

[82355]

Swap to some narrower rims would help.

I think 3.73's would be good with 33" tires and no overdrive. I would run a 4.10 with 35" tires. Off road won't be great with the high ratio in the Low Range of an NP203 though.

Have you looked into a 1" body lift?

http://www.offroaddesign.com/catalog/oneinchlift.htm

If you want a slight bit of tire clearance, with out the silly looks of a 2" or 3" body lift, it is a nice option.

Martin

 

[ktmoutfront]

Drop the engine in and drive it foe a while. See if it does what you are asking of it. Then figure oit what would be better. Witht the 33's, the 3.73:1 will be all around ok. Towing might not be the best, but no truck does everything perfectly.

 

[BloodMoon]

Thanks everyone!

I may just go with the 33s; known performance as well as clearance.

I was able to speak with the manager at the local tire shop, he is going to bring in a set of 35x12.50 and mount up a pair to see what kind of clearance there is. If the clearance is good I may just be pressured into them... (years of set minded planning of the truck will do that to a guy..)

I was able to locate a couple threads where people had similar setups. 35" and TH350, and it does look like 4.10 is the winner for what I am looking at but it appears that I could run 35 with the 3.73 for a while too? Just going to be a little slow from a stop; but with a new 383 stroker going in I think it may compensate a little? Thoughts?

If I go with the 35s what brand gears do you folk recommend?

Just thought you guys would find this funny and kind of sad, I found the date code on my current tires ~216; yep 3 digits, so that would make them at least 19 years old. So even though the tread looks good, it kind of forces my hand.

 

[tRustyK5]

I just had my next project delivered today. 57 Pontiac that had been sitting in a garage for 47 years after an accident. Three of the tires are brandy new looking. Found the receipt in the car, bought and installed at Sears, in late 1966...a few months before the accident. They look great.

 

[BloodMoon]

I just had my next project delivered today. 57 Pontiac that had been sitting in a garage for 47 years after an accident. Three of the tires are brandy new looking. Found the receipt in the car, bought and installed at Sears, in late 1966...a few months before the accident. They look great.

So you know exactly what I am talking about! There is totally life left in those things... good tread, no flat spots or bulges... maybe a few cracks but the cracks are small so it's okay!

 

[82355]

With a TH350, you'll be fine running a set of 35's with 3.73's.

Martin

 

[rjfguitar]

I am going to go against the grain here I guess.

I always thought the 4.10's with stock 31's in my K30 was about right, and I have a TH400/454 in it.

For me, I'd do 4.56's with 33's and 4.88's with 35's. That would put you right back in the range of a stock K20 or K30. I plan to go 5.13's and I have 35's, but I have overdrive too.

 

[BloodMoon]

I was able to measure the distance from the outside edge of the rim to the lugs and it measures at 7.5", so that would put my backspace at 2.5/3" depending on if the rim is 10 or 10.5, anyone know what the oem backspacing is?

Also, if I were to draw a straight line down from the fender tip closest to the door, it has about a 3-4" gap from the tire. And the from the front tip would have about 1.5" gap.