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1991 k5 lacking power?

wraenking

wraenking

1/2 ton status
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my friend just got a mint 91 hmc jimmy (hopefully mine soon) lol

we out a 4" lift with 35's underneath it and he said while driving in the highway he had to have the pedal to the floor to get to 65?


stock gearing, so im not sure if its that or not. we havent tuned it up yet either. hes not sure if hes happy with the truck, so i mget it and swap all my **** into it, but i told him i would check to see what it is


any ideas?

thanks guys
 
I would agree its probably gears . I ran 33's and 3.08's and I had to use 3rd until highway speeds , and then I had to downshift on any slight grade . Same tires and lower gears , albeit cheap factory 3.73 axle swap , and its ways better . My truck likes to pull the same grades in OD now , doesn't gear hunt and doesn't take much gas pedal now :k5: :k5:
 
Start with the fuel filter. I usually do not agree with throwing parts at a problem for troubleshooting but this part is cheap, easy, and probably needs to be done anyway. We can go from there....
 
pauly383k10 said:
I would agree its probably gears . I ran 33's and 3.08's and I had to use 3rd until highway speeds , and then I had to downshift on any slight grade . Same tires and lower gears , albeit cheap factory 3.73 axle swap , and its ways better . My truck likes to pull the same grades in OD now , doesn't gear hunt and doesn't take much gas pedal now :k5: :k5:
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I agree with the gears as well. Our '98 Dodge has 33's and 3.55 gears, and it can barely hold overdrive on the Interstate because it's barely turning 2000rpms at 80mph.

35's and 3.08's must be horribly painful.... it's like putting a set of 2.46's (if they even exist) with stock tires.
 
I wouldnt think it was the gears. My brother ran with 3.08's and 35's for almost a year and a half and it had power. His GPS said he was doing 107 down the highway one time. I would check the fuel filter if I were you. That could cause the problem. Other than that just do a tune up. New dist. cap, plugs, wires, air filter, oil change, clean the tbi, adjust the timing, etc etc. It should have plenty of power to turn 35's at 65 mph. Look in the glovebox to find out what gears you have. In 91, 3.42's were popular, which should turn 35's down the highway pretty easily.
-Harrison
 
87BrnRsd said:
I wouldnt think it was the gears. My brother ran with 3.08's and 35's for almost a year and a half and it had power. His GPS said he was doing 107 down the highway one time. I would check the fuel filter if I were you. That could cause the problem. Other than that just do a tune up. New dist. cap, plugs, wires, air filter, oil change, clean the tbi, adjust the timing, etc etc. It should have plenty of power to turn 35's at 65 mph. Look in the glovebox to find out what gears you have. In 91, 3.42's were popular, which should turn 35's down the highway pretty easily.
-Harrison
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;)
It should get to 65 eventually but be able to surpass it to a great degree with lotsa open road :eek:

Can it?

I have had the fuel filter go bad on mine with good gears and have extreme problems with getting to 65. Had the original cat go bad with similar problems also (go monolithic).
 
Even with 3.08's my brothers truck didnt get to 65 "eventually". It booked pretty good. Especially up around 70, if you punched it, it would move surprisingly well. But it does sound to me like a clogged fuel filter. Happened on my dads 99 suburban and it had no pwer from 30-40. Barely got out of its own way.
-Harrison
 
2Dogs said:
Start with the fuel filter. I usually do not agree with throwing parts at a problem for troubleshooting but this part is cheap, easy, and probably needs to be done anyway. We can go from there....
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fuel filter first. those tbi trucks should smoke tires when working good. the filter is about 5 bucks and easy to do.
 
hmmm what tranny does it have? If its a 700 that is completly normal when running 35's.... I had a fairly stock 350(about 230 hp) with stock gears and 35's mated to a 700 and it was gutless in 4th unless you got up more speed than 65. once you get past 65 it has a lot more scoot. I switched to a better higher hp motor mostly because i wanted to be able to hit the highway hills in od and maybe win a few mud comps and sand drags. I could have put new mains in my old stocker but i got tired of doggin it in 3rd everytime i hit a hill and i wanted better off idle torque and response. If he doesn't have the money for a motor buildup 4.56's will help ALOT with the 700.
 
Check your timing and check that all cylinders are getting spark. When I first installed my 33's with my 305 I could hardly go anywhere. I found out that 2 of my plug wires were arcing and one of the spark plugs had a cracked insulator and was arcing to the block. Running on 5 out of 8 cylinders decreases your power....alot! lol
 
Tom....

it wont be gears if it only gets to 65... more than likely some fuel or tune up issue... if he can be around your place sat, maybe i'll stop up and see you as opposed to you stopping by the shop..
 
Gearing, Gearing, Gearing!!!

You are going to have to cheat with that TBI motor because how badly those heads flow. You can do that with gearing, (or change the heads.) I went from 30's and 3.42's to 33's and 4.10's and I could def feel the difference. The difference is really only on the low end, the Higher RPM's suck. (My engine build will fix that though.)

I suggest you change gears regardless of how your engine is running. For 35's, go with 4.56 to stay close to a stock ratio.

Now the question is, do you want to spend money on a 10 bolt for gearing for 35's or do you start looking for a 14BFF with the needed gearing and build it right?

Lots to think about.

Good luck!
 
we out a 4" lift with 35's underneath it and he said while driving in the highway he had to have the pedal to the floor to get to 65?
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It depends on what that means, but that is normal with a 700 k5 running 35's. in 4th gear the motor is silent and until it spins up around 70 or 75 it will be gutless.
 
are you arguing with me again?

garauntee gears are not whats wrong.. sure it could use gears, but if you have to "floor" a motor to get it to do 65, its not gears.. and it has nothing to do with a 700 or 4th gear or gutless.. hes talking about getting it up to 65...
 
ryoken said:
are you arguing with me again?

garauntee gears are not whats wrong.. sure it could use gears, but if you have to "floor" a motor to get it to do 65, its not gears.. and it has nothing to do with a 700 or 4th gear or gutless.. hes talking about getting it up to 65...
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i will back you up buddy. my friend has 87 short box with 38x12.5x15 TSLs and 3.08 gears with gov lock rear and tbi with tired 305. he can smoke the tires and it goes great on street and mud. ITS THE FUEL OR TUNE UP PARTS. check them first. and if dark out fire up and look under hood and look for crossfireing on wires. easy to spot on dark night.
 
thats y i said.....

Quote:


we out a 4" lift with 35's underneath it and he said while driving in the highway he had to have the pedal to the floor to get to 65?





It depends on what that means
 
Not arguing with you, it's just my opinion that alot of his problem starts with gearing. He is working with TBI and a computer that's looking for certain info based on on his speed, throttle position. And yes, problems can be addressed with a simple tuneup, fuel filter change, etc. plus any other mechanical issues, but these are compounding this issue.

Fix all these mechanical issues and he will still have problems because of his drive ratio, gearing is just the most staight forward to address it.

When you have successfully trouble shot and fixed the problem, i'd be interested in the outcome.
 
i am not saying the gears are the problem but the tune up stuff is about 75-80 dollers total. and gears are 300-1000 for used axles or new gears. the cheeper fix would be the one i do first. then when sure running good do gears.
 
sweetk30 said:
...my friend has 87 short box with 38x12.5x15 TSLs and 3.08 gears with gov lock rear and tbi with tired 305. he can smoke the tires and it goes great on street and mud...
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Anybody can smoke tires in a pickup and a gov loc. There's no weight back there, c'mon.

I've got a 350 TBI (not so tired with 210HP 300ftlb), 4.10's, 33" and a detroit locker in my suburban and the best I can do is chirp the tires going into 2nd gear or turning a corning.

BTW, now I'm arguing.

Gees
 
dirtwarrior17 said:
thats y i said.....
Quote:
we out a 4" lift with 35's underneath it and he said while driving in the highway he had to have the pedal to the floor to get to 65?
Click to expand...

ok, i'll translate for ya... not too hard, 1 letter.. :p:

we Put a 4" lift with 35's underneath it and he said while driving in the highway he had to have the pedal to the floor to get to 65?

lets look at the key phrases here.... "pedal to the floor" and "to get to 65"

sounds like a 0 to 65 issue to me.. and it certainly doesn't sound anything like a tranny issue... it definitely wants a gear but i'd bet the farm its got a tune up issue causing the majority of that prob.. i'll find out saturday....
 
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