454 Burb

Ok this is the story I have a 92 GMC Surburan with a 454 and an auto tranny with overdrive. I have recently purched this with 84,000 org. miles on it. I put a 6 inch lift on it with 35 inch tall tires and it has 4.11 gear ratio. Now the problem when I pull a trailor (30 foot weekend warrior aprox. 6000 pounds)or run up a hill empty I have no power. The rmp's will not run up they sit around 2,200 (35 miles per hour)I sometimes hear something like an airplane somewhere under the hood? However down the hill and on too the flats away we go 3,400 rpms and 75 miles per hour. It just seems to have trouble under a load. I have replaced the fuel filter,plugs,wires,cap,rotor, and K&N air filter. The motor has been on a scope and every thing was ok. I just have problems under a load. Any Ideas greatly apprectated.

Brent

iTrader: (1)

The airplane under the hood is your cooling fan. The fan clutch engages when the temp of the air coming through the radiator is high enough.

snflupigus

needs a tuneup. maybe a manifold to give it some torque. and ..... a bigger throttle body. a snflupigus designed one.

Pukka

Is the tranny downshifting? Have you tried it with the tranny manually set to a lower gear with the same problem?

The oversized wheels may be causing the problem by affecting your final drive ratio, but I think this would affect acceleration all the time, not just under load

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92 Camaro RS, LO3, 5-spd, T-tops

Performance:
K&N Open Air Filter, Edelbrock performer TBI intake, Fastchip Prom, Timing +4 degrees, Centerforce clutch, Xact 8mm wires, SLP 1 3/4" Headers (coated), Flowmaster Catback Exhaust, Z28 Grille w/aftmkt fog lamps
Electronics:
Alpine 8030 Alarm System, Valentine One Radar Detector (How did I ever drive without one?), Pioneer DEH 7450 Head Unit w/6-pack CD changer, Pioneer DEQ 7600 Sound Processor, 2 Kenwood KAC-846 Amps powering 2 12" Pro Red subs, 2 Pioneer 6x9 and 2 MTX 4x6 speakers.
NEXT UP: TBI mods, 3.42 gears w/Torsen posi

454 Burb

[This message has been edited by 454 Burb (edited May 16, 2001).]

454 Burb

The tranny does not shift down. I can pull it down to second and the rpm's will hold around 3,800 then without warring the rpm's drop to 2,100 and I loose power?

JPrevost

If it's not down shifting then I would think the trans cable isn't hooked up. Check to see that it's setup right. Then I'd check if the trans is locking up or not, if it locks up early then your engine will bog.

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, Jon (350 TBI!)
91 Red My website

snflupigus

my trany kickdown cable came off once, lost all power when floored. hmmm didnt think of that could be your prob. i too vote to check that.

454 Burb

The tranny kick down is hooked up and the tranny will kick down like it should I belive. What I was trying to say is the loss of power just happens it does not seem to be affected by the tranny. It will hold the gear it is in, the rpm drop does not come from the tranny shifting.

[This message has been edited by 454 Burb (edited May 17, 2001).]

prscarf

i a running a 350tbi in a 1991 1ton 4x4 with the same gearing and rubber. mine is also a slug but you have to remember one thing, the truck is heavy and you are pulling a 30ft trailer. you have a pcm in your truck which controls the lockup and shift for the tranny. since you have a 454 i think you would have a good tranny, 4l80e. since your tc is unlocking properly when you stand on the throttle then everything there should be fine. you mention nothing about the exhaust! do you have a cat on and it may be plugged up, or the exhaust is just plain restrictive. you may also have a cam lobe worn, check your comp. process of elimination first. if this all checks out purchase a scantool and see what your engine is doing while you drive. i just did this with my truck pulling a 26ft trailer, the scantool works great for viewing all motor functions under changing load. i am using datamaster and a p75 laptop. now with all this said and done i just finished droping 5grand into a sbc 383 c/w extreme cam, trickflow aluminum heads, 10:1 comp, 454tbi and all the eprom programing equipment and scantool. this is so i can do exactly what your looking for, maximum torque brother!!! your 454 is a stock mild engine, i just sold one out of my other 4x4 with 35"tires and of course it had torque but not what i thought a bbc should have, mind you it was stock with headers and dual exhaust.