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I have a need for speed... well at least a little faster.

jimjafarian

jimjafarian

half & half
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Location
Syracuse, NY
So every day I drive to school and I have to go over (through) a mountain. This is not an exaggeration this is my approximate route. There is a max 23% grade on my route which is about a 13° slope and this is the hardest part of the drive and I am maxed at 45 MPH at high RPM's dipping down to 40-35 MPH, which is understandable for a stock 1990 jimmy on 33's with 3.73 gears. My problem arises when I am going home and the max grade is at 7% (6°) and I am still stuck a 45 MPH until it flattens out then I can hit 55 MPH. The fastest I have had it was 75 MPH down a hill full throttle. I don't think that the material which my foot is constructed of plays a role in the impotence of my vehicle as it is made of uranium and sinks the pedal through the floor. I am not expecting sports car performance out of a 5,000-pound bull with an old 350 in it but I am not certain if this is typical performance and what can I do to remedy it? Taller gears (4.10)? New 700R4 from monster transmission? New or rebuilt engine (only at 60,000 Miles)? I may be 17 and stupid, but something does not seem right to me.
 
Go through all the basics first. Check the timing, confirm the plug wires are in the correct order and do basic tune-up stuff. Then check the fuel pressure. Sometimes TBIs respond nicely to a bump in fuel pressure. Does it have the original catalytic converter on it? It could be plugging, which really kills power. What is the altitude? It's possible that engine just isn't going to make over 200HP up there. Probably no benefit from an engine or transmission swap, assuming same controls and exhaust (an LS swap is another story....).

Don't plot mods until you're sure everything you currently have is working right. The 4.10 gears would certainly be better (actually "deeper", the lower numbers are "taller"), sometimes going a single jump in gears isn't worth the large expense. 4.56 would probably still be OK with 33's with your overdrive since it seems the truck needs grunt in these conditions. Often swapping in another set of 10-bolt axles is cheaper and easier than the gear swap and setup, if you can find the ratio you want.
 
Aside from the things mentioned, use a better octane from a decent station

As a note, I run the TBI pressure at ~14 psi
 
gears are a good thing but not as easy as it sounds finding 2 10 bolts with 4.56 gears but this would wake the truck up along with things blue and bent both mentioned
 
You sure you have 3.73 gears. I had 33 with 3.08 and had the same problem. I went to 4.56's and 35 and climber the same grade at 70 in cruise and overdrive. this was to Donner summit in the Sierras of Ca. 5000 to 7000 ft of elevation.
 
The timing and the order are correct and I have already done the basics and everything is in good condition/serviced/replaced including the gears, trans, etc. I will check the fuel pressure and report back. The exhaust needs to be changed as it is the original cat and is rusted all to hell. The elevation is from sea level to 1,000 feet at its peak and the route is only about 10 miles one way. I am certain that I have 3.73 as I have the GT4 id in the glove box and have had them verified by a reputable shop. I have a GM 12 bolt 30 spline rear with a GM 10 in the front. I don't know if the 12 was a factory install as this was a police vehicle though it is not an M1009. I am not planing to make this an off-road machine 85% on road 15% light to moderate off-road so I don't want to go too crazy on the gears. The max I would go would be a 2 or 4 inch lift with 33 or 35 inch tires, with more of a stock look while still being semi capable. I would not want to get Dual dana 60's on 44's with 4 link and a 15 inch lift.

I also would like to say that although living in Hawaii sounds nice, and it is great, it is not the best place to find scrap yard well anything and everything cost a great deal more. This is not a permanent situation as I am going to college in the north east US, but bare in mind I only have about 2-3,000 dollars to spend on my rig at this moment.
Thanks for your time and effort and I am open to all considerations.

P.S Thank you for correcting my mistake "(actually "deeper", the lower numbers are "taller")"
 
bent72 said:
Aside from the things mentioned, use a better octane from a decent station

As a note, I run the TBI pressure at ~14 psi
Click to expand...

This would be difficult as 92 at my local gas station is $3.20 a gallon and $3.20 x 31 gallons is $99.20, that hurts my wallet just looking at it. I spend about $88 as it is.
 
Gearing is your main problem assuming like you said everything else is kosher. You could either regear, or find a 3/4 ton set of axles with 4.10s. It wouldn't be a significant jump in rpms, but it would certainly help on the hills and could be found "cheap" used. Cheaper than gearing your current setup. And 8 lug isn't much of a non factory appearance. Only someone who knows about the trucks would notice it.
 
The glove box tag means nothing unless you're the original owner. Did a shop verify that the gears are good, count revolutions or pop the diff cover and read the markings on the ring gear? Just have to be sure of the starting point. You can verify the ratio yourself with a couple jackstands and a couple pieces of tape if you want. Do you have a tachometer? It would help to know the actual engine speeds you're seeing and could also be used to calculate the ratio.

An old test for a plugged cat is to remove the O2 sensor and connect a pressure gauge there.

Also look at this thread: https://ck5.com/forums/threads/bad-catalytic-converter.329393/#post-3748491
 
Pop the diff and take a look at the gears. Its always good to pop the cover and change the fluid as part of maintenance.
 
I'd try putting 4 "stock" tires like 235/75-15" on it and see if it will go any faster up those inclines,after making sure the engine is in tune and breathing ok....33" ones are about 4-5" taller and will "up" your gearing accordingly..make your 3:73's feel more like 3:23's...

My '81 G10 van has a 2:73 rear axle I put in it when the original diff case hogged out the side gear bore--it had 3:08's,and I thought it was doggy with those gears--it'll go almost 60 mph in first now,and I can use second gear to pass going 65 mph (TH350)--but when you take off on an incline its slow,and feels like your taking off in second,or power braking it some!...
I wish I had chosen the 3:42 ratio diff at the salvage yard instead..but the 2:73's they sold me for 20 bucks,no one wanted it and it only had 35K on it...it would be great if I lived in flat open country like Kansas,not so hot here in hilly New England..
 
I agree check the gears.

I have a burb with a 6.2. I drop to about 40ish on a 7% grade that's a couple miles long but that's at 6500 ft not at sea level. Well the bottom is 6500 ft the top is over 8k

That's with 3.73s and 32" tall tires
 
I was on that route last summer in a minivan and six passengers with no slow down, The top of that grade is a tourist stop to see the spot of the greatest battle in Hawaii history. That road should not slow your Blazer that bad.
 
frankin5 said:
I was on that route last summer in a minivan and six passengers with no slow down, The top of that grade is a tourist stop to see the spot of the greatest battle in Hawaii history. That road should not slow your Blazer that bad.
Click to expand...
That why I came here. I have gone up that hill thousands of times in all different cars and trucks and never had a problem. Don't tell anyone but I have hit 100 plus on that road in a 2015 Passat with a 5 speed and a 1.8 turbo 4 cylinder so it's not that intense of a drive. Driving slower does allow me more time to soak up the view but it means that I have to leave 10-15 min earlier every day.
 
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