Losing power/slipping belts?

[iamseth]

hello, new to this site, here's my first post:

I have a 72 chevy 400 big block. Lately I feel i'm losing power when going up hills, or that the trans is not shifting. So when that happens the RPM's get higher and I hear this screeching noise. I've been told that it's a belt slipping, but I can't seem to find it.

Can anyone point me in the right direction??

thank you

[swamp rat]

is it an automatic or standard tranny? I'm assuming automatic.

If you can make the screeching noise while stationary and reving the engine than yea probably the belts.

Loosing power on uphills and the rpm goes up: (Assumption that its an automatic)

You should be able to know if its not downshifting, if its not than the kickdown cable is not adjusted properly or there is an internal problem in the tranny.

check tranny fluid if an automatic, does it smell burnt? look black or dark brown? of it does than you may have a tranny problem.

[ChevLoRay]

to the board from the Heart of Arkansas!!

Belts can squeal because they're old, or it could be you have a bad bearing in the alternator that is putting a drag on the drive belt. If it is the power steering belt, you'd have the squeal when you are turning the steering wheel at a slow speed, as in parking your ride.

But, the suggestions for the transmission above are also a good place to start.

What size tires on the rear? Taller tires (larger diameter) will affect how it performs going uphill. Are you carrying anything in the bed?

How long have you had it, anyway?

[iamseth]

thanks for the responses!

the trans (which is automatic, 3speed) fluid is red and full. Not burnt or anything. It does downshift (or at least it feels like it is), but thats when i lose the power and the screeching starts.

When in park, I can re-create the screech by reving the engine. AND when i turn the wheel hard left or right, it screeches too. However, I recently changed the power steering belt. Actually, i changed the alt belt too. Could the belt not be on tight enough? Or is the pwr steering pump going out?

[swamp rat]

Its a common problem to have a screetching belt on these trucks, i have been fighting it for a long time, new belts, new repop pullies new alt and i still have a problem with it, its frustrating to say the least. I have thought the angle of the belt going across the water pump pully and the lack of surgace contact may be the culpret, but i have not incested in a fan clutch yet to see if that helps. I have a rebuilt PS pump as well.

Do you have a 4 barrel carb? Is it possible your actually feeling the secondaries kick in too early and not the kick down on the tranny? and possibly not jetted correctly? Or possibly the fuel filter is in dire need of changing and you have a bit of restricted fuel flow? does it feel like its surging?

[iamseth]

You know, I'm pretty sure the carb needs some work. I've got a rough idle and smells rich. Got a new carb kit and float and plan to pull it apart this weekend. Hopefully that will do the trick. I will look into the fuel filter as well.

Do you think it could be both the carb and tranny? Last night I put it in reverse and gave it a little gas.... nothing. It felt like the trans was not engaging. But if I just let my foot off the brake, it reverses fine. I don't know what that means.

Any ideas?

[cdowns]

have you had a major tuneup done to address your power loss/that's the first thing i'd do

[ChevLoRay]

My personal feeling is that it isn't the transmission. Since you say you changed those belts, my bet is that you didn't get them as tight as you needed to have done. If you have a pry bar, find a good leverage point and use that to put a little more oomph on it, then tighten it down. Having three arms makes it easier, but sometimes you gotta get by with just the two that God gave you.

Carburetors that need to be rebuilt, can definately affect your power. Like the suggestion for a tune-up.....a rebuilt carb can be a plus. The fact that it runs rich (black smoke) means your plugs are getting a generous coating of carbon on them, and they will not perform very well. That will result in a poorer spark, and it will just add to the poor performance and the black smoke you are seeing.

What kind of carburetor is on your truck? I'm guessing a Q-Jet. If so, there's a very strong possibility that the plugs in the float bowl are leaking fuel into the secondaries. That would be a "normal" problem for an older Q-Jet. It is also one that is easily fixed with or without a rebuild, but you do have to pull the carb off of the engine, turn it upside down and remove the throttle plate. When you do, you'll see two "wells" that have lead-looking plugs in them. The cure is to use new plugs from NAPA that also include o-rings and spongey pieces that also help hold these plugs in place when you re-install the throttle plate and tighten it down.

[allengator]

I think your belts slip because the RPMS are shooting up...
Just like if you had it in park and hit the gas!

Sounds like your trans is slipping...

[BB72CHEVKT]

Sounds to me like the tranny is starting to go out.