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

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 only problem with just finding a different rear is that there are no old junk/salvage yards and it's hard to find such rear ends as most drive Tacoma's here in HI. I will be regearing the axel (12 bolt) with new parts, now the only question is what gears to get and from where. Finally, the only problem with changing to an 8 lug is that a great deal of money with wheels, shipping, etc, maybe in the future I still have a lot of time with this truck.
 
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 will do and report back to you. Any recommendations on what gears to get and where from. I'll be in upstate NY or North Carolina soon enough, but I would have to drive it across country first (Long beach,CA) to either one.
 
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
Yes on all accounts except for the tachometer and have not tried the O2 trick, but will get a new exhaust system from heads to the tip in the likes of short or mid length heads to a "High flow" cat and glass packs or some other louder but not obnoxious alternative. While I am not the original owner I bought it from the Department's Mechanic and have been told it is all factory except for the bumpers, trailer hitch, winch, and tire diameter.
 
1990 was 10 bolt front and rear axles .

so if you have a 12 bolt rear then stuff is NOT original .
Yeah, I saw that when I was researching. They had not put it on the jimmy/blazers since the 80 or 81 models. I still was not certain if HPD (Honolulu Police Department) had just ordered it special since it was part of a batch of 10 or 15 custom blazers/jimmy's that were ordered by the City and County of Honolulu for fire, water utility, and police usage. They all had 12 bolt rears and that is why I do believe that is a factory install along with the dual batteries and different fuse panel (it has the panel of a 1990 k2500).
 
I might be the first to say it, but I'd like to see some pictures of this rig. It sounds like a pretty cool /special setup.
Just to add the two cents, I'd verify gearing and increase as required as long as the engine tune up bits are in good order.
 
When GM quit using the 12 bolt they also quit making it.

A 1990 blazer having a 12 bolt would not be factory.

If you post pictures we can verify it is a 12 bolt.

Have you checked compression on the engine?
 
Sorry to bring up a dead thread, but my condition has not improved. I have changed the fuel pump and sending unit, New manifolds, 3 inch full exhaust(Small universal Flow master cat, Straight through Borla muffler), Timing chain, water pump, and the truck runs great(Can pass people at 65 on flat ground). The truck moves quick off the line but once it shifts to second the engine sounds like its is bogging and under heavy load at WOT from about 20 to 30 MPH even on flat ground, at 30 MPH the power comes back. I verified the gears to be 3.73. I am planing on changing the gears to 4.56, this will help but not a solution, and will do a compression test. I need help with this one because I still can go up the hill efficiently.


Original post:
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 (60,000 Miles) in it but I am not certain if this is typical performance and what can I do to remedy it?
 
Before you spend a lot of money on gears, see if you can't borrow some wheels and tires. That is the easiest way to "test" gear ratios without actually buying gears. You don't have to have them longer than it takes to go over the mountain and back.
Get some stock size or smaller tires, and see how the truck performs. If that cures it, then you can do the math to see what gears would give you that final ratio with whatever size tires you want to run.
If it still bogs, then don't put the money in gears until you figure out what is really wrong.
Anything that will fit your truck will work, surely you know someone with a car or truck that would let you use their tires for a couple of hours. Especially if you do the work. Offer to rotate them and get them balanced for the use.
 
I agree with that---if the smaller tires don't seem to help much,it could be something else--I've seen a few automatic transmissions that had the stator in the torque converter "lock" and cause poor acceleration between 25-40 mph,it sort of felt like the e-brake was dragging until you get it over a certain speed..

I'm betting its more related to the altitude and the engine just being less efficient as a result..just about all the trucks I've owned fely much peppier and powerful at sea level where I live,compared to when I drove them to NH or VT ,NY,where the mountains are much higher altitude..perhaps some tweaking to the timing and fuel mixture might help some..
 
How did you verify the gears? My 90 Blazer with a tired TBI 350, 3.42's and 35's had no trouble pulling 4000 lbs of trailer through the mountains of British Columbia at the posted speed limit with power in reserve...
 
It sounds like you plan to keep the blazer a while. You plan to drive it around the mainland too.
I say wait to do the gearing and whatnot until you hit the mainland. It will be cheaper and easier to find shops if you can't do it yourself. As a bonus, you can grab a set of axles with the right gearing for cheap, cheap enough to have money left over for the 8 lug rims you'll need. You'll be ahead of the game then. Just saying, do the cheap or free stuff now and wait till you're over here to do the larger stuff.

I second a compression check. Never know.
 
and make sure you are getting each gear in the trans . count the shifts . or man select each gear . it could be a trans problem and skipping a gear and bogging down the vehicle.
 
It sounds like you plan to keep the blazer a while. You plan to drive it around the mainland too.
I say wait to do the gearing and whatnot until you hit the mainland. It will be cheaper and easier to find shops if you can't do it yourself. As a bonus, you can grab a set of axles with the right gearing for cheap, cheap enough to have money left over for the 8 lug rims you'll need. You'll be ahead of the game then. Just saying, do the cheap or free stuff now and wait till you're over here to do the larger stuff.

I second a compression check. Never know.
I will have to wait until at least this time next year before my truck will reach the mainland unfortunately(Long beach, CA then to Syracuse, NY). I will be a freshman at syracuse this fall and will not be able to have a vehicle for my first year. I do plan on keeping this jimmy as long as physically and finically possible as well as it will be my daily driver for the foreseeable future, I also spent a grand getting a Softoper so I want to get my moneys worth($100 shipping alone). I know that most of the major stuff ( engine, tranny,body work, etc) will be cheaper and more accessible on the mainland, but I would like to be able to possibly drive it across the country even if it will be a little impractical.
 
How did you verify the gears? My 90 Blazer with a tired TBI 350, 3.42's and 35's had no trouble pulling 4000 lbs of trailer through the mountains of British Columbia at the posted speed limit with power in reserve...
I have verified the gears in 2 ways, rotating the tire and watching the drive shaft rotations(with both wheels spinning), and the shop that did the pinion seal counted the teeth(per request). There is a possibility that I have some how gotten this all wrong, but I find the unlikely. This is also why I think that the gears may not solve the problem is because most seem to have no trouble at all, and this is not a troublesome hill in the least.
 
OK, I guess we beat the gears question to death. Have you done a compression test on the engine?
 
I agree with that---if the smaller tires don't seem to help much,it could be something else--I've seen a few automatic transmissions that had the stator in the torque converter "lock" and cause poor acceleration between 25-40 mph,it sort of felt like the e-brake was dragging until you get it over a certain speed..

I'm betting its more related to the altitude and the engine just being less efficient as a result..just about all the trucks I've owned fely much peppier and powerful at sea level where I live,compared to when I drove them to NH or VT ,NY,where the mountains are much higher altitude..perhaps some tweaking to the timing and fuel mixture might help some..
The feeling in the truck when it is bogging is not the feel of the ebrake but rather just a flat spot in the acceleration because it will be pulling then all of the sudden it will lose its pep. I just took it for a drive and I am fairly certain that I do not have second gear; The tranny shifts out of 1st (to I think 3rd) ,but does not shift until overdrive after I lift off the pedal at 50 MPH plus. I live at sea level and the elevation change is not enough to affect the performance that greatly.
 
To check the transmission, pull the shift lever all the way down and manually shift it through the gears as you accelerate...

It could be your TV cable is not set right and it's shifting way too early and not kicking down like it should.
 
i live 1hr 45min south of Syracuse university . . don't plan on driving it up here in the winter or the salt and liquid de-icer products they use in the winter will eat that truck alive . and the area you are going to school is the SNOW BELT zone . they get LOTS of it .
 
To check the transmission, pull the shift lever all the way down and manually shift it through the gears as you accelerate...

It could be your TV cable is not set right and it's shifting way too early and not kicking down like it should.
You could be right that the TC cable was not set right because IT WAS NOT CONNECTED AT ALL!! All this time and the fix could be that simple. Its always the simple things that screw you over. Im going right over the hill right now to see if its solved.
 

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