The river here is frozen 5 feet thick. It is absolutely flat. I used to own a 1988 3/4 T 4x4 Suburban and could go 85-90 mph in 4-wheel no problem. It had a 350. My wife's truck I can easily run right up to where the wind resistance overcomes the tire traction (70mph), in 2x4 and in 4x4 can go as fast as I desire. It is a 1/2 T 1994 Ram with a 340.
So I am on my way to pick up Mother-In-Law and I slowly press accelerator down. 65mph is it. I press the pedal right to the floorboard where I can feel I am ready to engage the manual kickdown. Don't want that as it'll spin instantly. I slow way down engage 4-wheel and take it back up. On a straight stretch running almost 10 miles, I have the pedal absolutely to the boards, and it will hit 68 mph and that is all. The engine is running 2600 rpm exactly. The first time it kicked down it hammered and rattled enough to really scare me, the second time it kicked down it was markedly less, and the third time I must have blown all the carbon out as it was running smoothly. But it will not go past 2600 rpm or 65 mph. Period. Pressing the pedal down has no effect, but a very slight lurching as if something is holding the motor back. And this is with a 2001, 488 cube V-10. I have more power and torque than both the old Suburban and my wife's rig combined. I should be able to take it 'till losing traction via the 4-wheel. I am wondering what may be the problem. If this is affecting high-speed performance, it may explain the unreasonably crappy 6.75 mpg in-city effiiciency.
When I first bought this rig, I drove it from Fairbanks to Anchorage Alaska (480 miles), at 75-85 the whole way, up-hill into the mountains between the cities, and into a 20-35pmh headwind as a huge storm was sitting on the middle of the state at that time. I made 13.8 mpg. And this is with zero mods, no headers, high-flow muffs, K&N ect.

Any ideas?

Thanks.

 

rev and speed limiters, they are pre programmed into the computer. A reprogrammer will reset these but always obey the posted speed limits

 

did you even bother to read his post? the rev limiter is not set at 2600 rpm. not even close. and a speed limiter at 65 [:@]. you're wrong by far.


nitroman, you need to provide some more details i think. can you rev past 2600 rpm at idle? if not you could have a clogged catalytic converter.

oh, and if your wife truck has an original motor, its either a 318 or a 360

 

I had this same problem with my truck (in sig) It kinda just happened out of no where I couldnt go over 60mph and the rpms would go to like 3000 but It was the revs were going out the window, no power what so ever I took it to the dealer and my Cat was under recall, so they replaced it FOR FREE and it completely fixed the problem I have no idea if this is your problem since you engine is more massive then mine but just sharing my experience to hopefully help shed light

 

If the clogged cat isn't your problem, try checking your spark plug gaps. They may be too wide.

 

Has any maintenance been done, any at all?
That would be my first guess...

Because this sounds exactly like a car that hasn't had even the oil changed in at least 50,000 miles.

 

sounds like either intake or exhaust is restricted, most likely exhaust/cat. an easy test is to remove the pre-cat 02 sensor just to see if it helps. on the intake side, make sure your air filter is not stopped up.

 

Ok, let's see. I bought it from the dealership and it had had a tune up, the usual dealer stuff, back in August. SO that would be six months ago. Hmmm. Time to do the tune-up then. I'll try that O2 sensor trick and see what happens. I will try to see how high I can rev it....within reason. Maybe 4,000 rpms.

 

I tried increasing the rpms and it goes easily to 4000. I didn't try any higher. I will have to get it into the shop.

 

is that with or without the pre-cat o2 sensor ?