gear ratio in a k5

I recently purchased a 1991 K5 350tbi 700r4 241c with 33" tires and 3.42 axles. The K5 doesn't seem to run properly because i would guess the gear ratios. As soon as i get on the highway and gets into OD it changes out and in when I approach a small slope. Engine runs fine good compression, trans is rebuilt so i'm guessing its the tire axle combo.

What gear ratio would be recommended and how easy/hard is it to change them out? It's all stock except 3" body lift.Really like the K5 just don't feel like sinking any major money into it. Any help would be appreciated  

the gear issue i think would only affect if you had 35s 33 on a stock set up is norm
it sounds like you have a fuel issue, possibly the fule filter(very common) or worst fuel pump take the filter off and blow through it.  if its not easy as reg breathing then its pluged and in need of replacement  
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You know I love you all (in a manly non sexual way) Spawn_X

I'm gonna go ahead and try changing it out without even checking it. Its the only thing i didn't change out when I did a complete tune up. If it still acts up on slopes i'll be back for more suggestions. Thanks.  

Ratio is way low. Go with at least 4.10 to 1. As for doing switch if you don't get it shimmed right you can ruin new part real fast. Go to Randy's ring and pinion web sight and they can set you up with all the know how you need. Good luck and keep us posted. As for being a fuel issue this is easy to test. Take truck for a ride and leave it out of overdrive. Drive it at 55 mph. If it runs fine then it is not fuel related. If it runs like crap then it is a possible fuel delivery issue. This is a easy test and is free.  

Well it wasn't the fuel filter. Runs fine in 3rd gear and once in OD and slight hills it slows down then downshifts. I'm mechanically good at putting things together but never took and axle apart or together. How hard is it to change gears besides the difficulty in the shims?

Or should I just buy used 3.73 axles and would it be worth it in the long run?  

I don't think you're going to get your desired effect with 3.73 gears. I wouldn't go lower then 4.10's with the possibility of using 4.56's. This isn't going to be cheap just for parts(I don't know how deep your pocket is) Randy's ring and pinion! Get book on your axle and decide if you think you can do the switch.Also get prices on parts. Get book and have fun.  

why would you go so high with such a small tire. the only advantage i would think would be cruising speeds and if he decides to go up to a 35.  do have the ability to check fuel psi. also have you given the vehicle a tune and adusted the spark plugs correctly.  whats the max speed. if its around 85-90 then you may have a gear issue also is it a 2 wheel drive, what does the door jam say for factory size tire  
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You know I love you all (in a manly non sexual way) Spawn_X

If you haven't done a tune up to it then you really can't go wrong doing one. If the ignition wires are bad then it can cause a slight shuttering at cruising speed. You can check the fuel pressure Blazer suggests to see if it's low or drops after running. I do not think these are the problem from the symptoms you discribe.I can agree with Blazer that 4.56 gears might be a little overkill but still think 4.10's are your best bet. The vehicle is older and probably not as strong as when new so gearing would help. If you have a tach in truck what are your rpm's at 65? If they are around 1700 to 1800 then gearing will help. Good luck and keep us posted.  

ya that make sense.  im thinking that the fuel psi might be not be high enough to floor it fuel pumps have many ways of dying one of them being decrease in psi especially under load.  the same thing with the spark plugs and especially the wires under a heavy load the spark could find another place to spark white spots on a wire is usually the symptom  
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You know I love you all (in a manly non sexual way) Spawn_X

After driving the Blazer today for over an hour and around town and on the highway it actually runs betters and doesn't down shift likes it used too. It had a full tune up about 4000 miles ago. Seems the fuel filter did help a little bit.

Now as far as for plans on the K5 I use it for daily driving, once in a while some mudding and no towing what so ever. When at full capacity max 5 people and sports junk in the back and a/c on i would like more power. What else can i do before looking into 4.10 gears?

Not looking for high performance, just good mpg and reliabilty.  

anything higher than a 4.56 is a waste of time and money for 33's... the OD ratio of the 700 is .699, higher ratio's like 4.10's will contribute to an early death of the tranny by baking it

I would (and do) run 4.88's  
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I've got an '85 K5, 350 w/mild cam, headers,edlebrock highrise and carb.
700R4 w/shift kit - 208 t-case, 35" tires.

It came with a GM corp 14 bolt rear w/ 3:73 gears.  It actually runs down the highway really nice, but I use it mainly in the dunes at Silver Lake.  I have to keep it in 4 low for the hill climbs but so far no problems.
I can't complain about the highway performance.  I drive it over 100 miles on the expressway every year and it's got more power than my 99 Silverado.

From everything I've read I'm leaning toward the 4:56 gear set, and seriously considering a full spool front & rear.  If I blow it up before I replace the gears I'll opt for a Ford 9", or go junk yard shopping for some 1-tons.

Let me know what you end up with for your gear set.  

K&N intake and filter
headers

i have a 97 tahoe 2wd and when i run a full load the power is still decent but it gets squirmy  
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You know I love you all (in a manly non sexual way) Spawn_X

4:56 at least!!! i have a blazer with the same tranny....people said that 4:88s would be way too low for my 35s.....they were way wrong....i can run down the fastlane on the highway in 4th gear no prob motor is right in its sweet spot too,not over reved and not lugging.....  
solid axle chevys cant be beat
78 K5: 350 V8,700r4,np208, 8 lug D44 4:88, 14 bolt 10.5 4:88 with detroit locker and 35 inc parenelli jones dirt grip tires

i wouldnt worry about the gears unless your moving up to a 35  
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You know I love you all (in a manly non sexual way) Spawn_X