No power driving up hill

[Blazer Ralph]

Hey new guy here! I’m hoping I can get a little help! I just bought my first blazer few months ago, it’s a 1982 k5 with a 350 and I was told has a th350 transmission. The problem I’m having is it runs good on flat streets but when I go to drive up a steep hill the truck feels like it has no power, like it is crawling up a hill. Took to mechanic shop and they stated it’s because the truck came with a 700r4 transmission and transfer case. Is this true or any other ideas?

 

[Wes Harden]

How long and steep are these hills ? Is your blazer hauling any load or trailer ? Which ever trans it has shouldn't effect speed on hills. Gears, tire size and Horse power are needed to climb hills.
So lets start by
1 current tire size
2 rear axle gears ratio, look in glove box and see if the production option list sticker is still there (aka RPO codes)
3 condition of engine, any over heating, hard starting, miss fires, uneven idle ?

Welcome to CK5 @Blazer Ralph

 

[Blazer Ralph]

The hills aren’t crazy steep, they are paved hills. I’m not hauling anything and I did a full tune up and I put new fuel pump distributor cap rotor all spark plugs new, belts new. Truck drives good! I drove it for 3 hours straight on hunting trip just going up hills she loses power. It does have 34” tires on it that previous owner put on that are new, mechanic also said those could be an issue? I have a feeling it’s the carburetor just wanted more opinions before I changed it

 

[Bent77]

Elevation? And how much higher from where it was tuned at?

 

[Wes Harden]

yeah is the 34's, cause I am betting the diffs don't have 4.10 ring and pinion. does the trans down shift on the hills ?

 

[Blazer Ralph]

yeah is the 34's, cause I am betting the diffs don't have 4.10 ring and pinion. does the trans down shift on the hills ?

No I don’t feel it down shift. I believe the differentials are original, I changed fluids. I’ll start with the tires. Thank you

 

[muddybuddy]

If you can count driveshaft rotations for a single tire rotation that would be a key to tell what your gear ratio is, im betting it may be 3.08 which would absolutely be a dog on hills with 34” tires. 3 rotations = 3.08’s, 3.5 rotations = 3.42, 3.75 rotations = 3.73, 4 rotations = 4.10’s.

 

[dyeager535]

Tires are pricey, does the shifter actually work? Can you get all three gears if you manually shift?

Agree its probably 3.08's, IMO tires alone aren't going to solve your hill climbing issue if its's not downshifting. Try manually downshifting. If the assumption about 3.08's is right, if you are trying to climb hills without downshifting, you'd be sitting at~1900 RPM's at 60MPH, and at 35MPH ~1100RPM.

With my '83 K5 that had the 700R4 and 3.08's with only 31" tires, I'd hold it in second gear a LONG time getting onto the freeway. It would upshift way too early, no matter how far the gas pedal position.

 

[tarussell]

As mentioned earlier by a few folks verifying that the carb is tuned right for where you live is important but it very much sounds like you have a lack of gear ratio problem.
If you do have a super low numerically gear like 2.73 or 3.08 in conjunction with a 34” tall tire then there’s your smoking gun.
Those gear ratios were gutless with the 29” tall tires that were standard equipment and a 34” tall tire is pure torture.

If your truck still has its original axles and gears it would have come with any of the following gear ratios 2.73 ( these were standard ), optional 3.08 and 3.73 ( optional only with a towing package ).

Even if you have 3.73’s those gears combined with that tall of a tire and any engine from the eighties emissions era is going to result in beyond poor performance expectations.

Here’s a pic out of a sales brochure for an 1982 model K5 or K10 with a gas motor that shows you what was available.

Getting your carb healthy is always a good idea but chances are you are way under geared for the tire size that you are running.

 

[Blazer Ralph]

Elevation? And how much higher from where it was tuned at?

 

[Blazer Ralph]

I’m having issues with hills by my home and I’m at about sea level, I’m in California. I drove it to about 7000 ft above sea level. It drives good it’s just as soon as there’s a hill it has no power, it’s crawling up

 

[Blazer Ralph]

If you can count driveshaft rotations for a single tire rotation that would be a key to tell what your gear ratio is, im betting it may be 3.08 which would absolutely be a dog on hills with 34” tires. 3 rotations = 3.08’s, 3.5 rotations = 3.42, 3.75 rotations = 3.73, 4 rotations = 4.10’s.

 

[Blazer Ralph]

I will try and count

 

[Blazer Ralph]

Tires are pricey, does the shifter actually work? Can you get all three gears if you manually shift?

Agree its probably 3.08's, IMO tires alone aren't going to solve your hill climbing issue if its's not downshifting. Try manually downshifting. If the assumption about 3.08's is right, if you are trying to climb hills without downshifting, you'd be sitting at~1900 RPM's at 60MPH, and at 35MPH ~1100RPM.

With my '83 K5 that had the 700R4 and 3.08's with only 31" tires, I'd hold it in second gear a LONG time getting onto the freeway. It would upshift way too early, no matter how far the gas pedal position.

 

[Blazer Ralph]

It does shift manually

 

[Blazer Ralph]

As mentioned earlier by a few folks verifying that the carb is tuned right for where you live is important but it very much sounds like you have a lack of gear ratio problem.
If you do have a super low numerically gear like 2.73 or 3.08 in conjunction with a 34” tall tire then there’s your smoking gun.
Those gear ratios were gutless with the 29” tall tires that were standard equipment and a 34” tall tire is pure torture.

If your truck still has its original axles and gears it would have come with any of the following gear ratios 2.73 ( these were standard ), optional 3.08 and 3.73 ( optional only with a towing package ).

Even if you have 3.73’s those gears combined with that tall of a tire and any engine from the eighties emissions era is going to result in beyond poor performance expectations.

Here’s a pic out of a sales brochure for an 1982 model K5 or K10 with a gas motor that shows you what was available.

Getting your carb healthy is always a good idea but chances are you are way under geared for the tire size that you are running.

View attachment 487938

 

[Blazer Ralph]

I really appreciate all you folks knowledge, I’m no mechanic whatsoever. I will definitely get smaller tires and have the carburetor tuned. Thank you for your response

 

[Bent77]

I’m having issues with hills by my home and I’m at about sea level, I’m in California. I drove it to about 7000 ft above sea level. It drives good it’s just as soon as there’s a hill it has no power, it’s crawling up

Ok you have 2 problems

First is gearing and tire weight

Second at any elevation you lose power. At 7000’ feet you lose roughly 30%

 

[Blazer Ralph]

yeah is the 34's, cause I am betting the diffs don't have 4.10 ring and pinion. does the trans down shift on the hills ?

Ok you have 2 problems

First is gearing and tire weight

Second at any elevation you lose power. At 7000’ feet you lose roughly 30%

Ya I’m going to get new tires this weekend, so I’ll start there. I did purchase an edelbrock 1400 with egr compatibility that I haven’t installed yet so that might be my second thing to do. Thank you very much for your response’s I really appreciate the help and knowledge

 

[ktmoutfront]

If you are driving to Big Bear with 2.73:1 gears and 34" tires, it will struggle heading out of San Bernardino. When you get to 4000 feet, it will be an absolute dog. I bet it is blowing a little black smoke out the tail pipe by then.

When i drove my 78 up there to spend a week working, decades ago when gas was better quality, I stopped at 5000 feet and re-jetted the carb. Changed it back when I headed home. With today's fuel, I bet it is worse.