My friend & I both have 3-speed gen 1's. Mine is a 4x4 & my friends is a 2wd. When I drive over 65 mph, I really have to fight with the throttle to keep it there. My friend's truck just sems to cruise effortlessly at 75+. His runs quiet & smooth. Mine sounds like I'm torturing it. I don't know the history of his, so I don't know if the governor has been tweaked. If the governor is raised, will that make it run smoother at higher rpm's or will it just rev higher? I just figured that with a 3-speed, fighting the rpm's came with the territory, until I drive his. Can anyone think of any explanation why the difference? I sure would like mine to run like his.

 

The difference is probably in your rear end gears (i.e. ring and pinion) His either came with a lower ratio than yours from the factory or he swapped them out. Im almost positive that just raising the governer will simply let it rev higher, and wont contribute to a smoother running engine at higher rpm's. Mind that if you swap out the rearend gears in your truck, you also must put the same ones in the front end if you ever wish to use 4x4. Check out the rearend on your truck and on his. On the cover there should be a small tag with the ratio stamped into it. While yours might read something like 3.73, his will most likely be much lower, like a 3.07 or something like that. That would cause him to have a much better top speed, while it would hurt his low end grunt. Your truck on the other hand would have much better grunt, but will peg out at a much earlier speed. Let me know if this helped at all.
Brian

 

Thank you very much for your reply. We both have 3:07 gearing. The next test I am going to do is to take my handheld gps in his truck to see if his truck is really going 75+. I got his truck up to 80 & it was still smooth & quiet. My foot-to-the-floor speed is 77.

 

what size tires are on each truck?

 

The speed difference is probably because of the air. The 4wd is much higher and pushes more wind.
-Jim-

 

dude, if your top speed is 77 then you have lower gear than 307. its more like 411 gears. my foot to the floor speed is also 77 and sounds just like what your describing.

tires would also make a difference, if one has little tires and the other has big ones, that would throw off the speedo and the one with big tires would use more power to go.

also your 4wd could be the 'heavy duty' version, that combined with the fact that you have to turn your transfer case gears as well as the usaul stuff will hurt top speed. are you front wheels locked in? that also steals for top speed...

 

I guess it's possible that the gearing could have been changed to 4:10. The tags show 3:07. The tach, if it's correct, shows 1850rpm at 55mph. the tires are stock, same as my friends truck. His truck has over 300,000 miles on it & I have 192,000. His doesn't smoke at all & is quieter at idle. Mine has some white(not blue) smoke at idle & sounds like a popcorn machine. Mine also does something else strange, it shakes, the idle goes down & sometimes stalls if the nose of the truck is pointing up on a hill. If I back down my steep driveway in neutral or reverse & hit the brakes, the truck will stall or almost stall & shakes badly any time the nose is higher than the tail end. Also, no matter how cold it gets out, the manifold heater has never gone on, but the truck starts right up with the first revolution of the starter. Fuel economy is good. about 18 combined & 21 if all hwy. If I tow up a hill, I'm always in the slow lane & in 2nd gear. Thanks for all the suggestions. I'm going to check the throttle linkage for full throttle. I'm sure the transfer case adds some additional frictions & it does sit higher that a 2wd, but it has not been lifted above stock height. I keep about 60psi in the tires. I'm thinking there might be wear on the injectors causing the idle smoke. & wonder if that could be affecting by top speed & affect the smoothness of the engine. Thanks again for all the respones, keep them coming.

Steve

 

If it weren't for the fact that the truck starts easily, I would be sure that the timing was retarded too much. You should NOT have white smoke at idle when the truck is warmed up (white smoke when it is cold could be the result of a malfunctioning KSB). The idle problem with the nose pointing uphill makes me wonder if you don't need a re-built injection pump -- that should NOT be happening either.

It sure sounds as though you have a fuel delivery problem. If I only had one guess, I would say you need a new injection pump, but it could be a timing problem, or maybe an injector problem. I would suggest a thorough going-over, starting with listening to see if one injector is louder than the others at idle/low speeds, then checking out all linkage adjustments, then KSB operation, then lift pump pressure, then pump timing, then bench testing the injection pump.

This will address the noise and vibration problems.

Your top speed seems about right at around 80 with 3.07 rears and no overdrive. I think if you get the engine tuned, you will be able to go a little faster, and it will be a lot more comfortable.

Good luck.

 

I guess I'd say lift pump first off. If pointed up hill it wants to stall, the injection pump could be having trouble pulling fuel through a faulty lift pump

 

Thanks again for the responses. It could be both the injection pump & lift pump. I have a Dahl inline filter that could be adding backpressure to the fuel delivery. The last time I changed the filter, it didn't stall as much with the new filter element.

 

humm, guess i was wrong about the gearing. i could have sworn i had a lower gear than 306...

sorry.

 

I am very appreciative of any and all input. I'm on a mission to make my truck keep up with the other traffic. Thanks again.

 

My '93 tops out at about 90-95 that is fast enough for these ol boys

 

Mine tops out in the 90's also. I would change the lift pump just for good measure since it doesnt cost much $$$ then go from there.

Paws

 

The difference between the 3.07 rears and a 3.54 rear is like having an OD ratio of .87.

The Getrag OD ratio is .77

The NV4500 OD ratio is .74


I made my road speed calculations assuming 688 revs per mile -- this is different depending on tire brands & treads, let alone tire size.

3 spd auto or .87 OD: 80mph=2,825rpm
.77 OD: 80mph=2,500rpm
.74 OD: 80mph=2,403rpm

By my calculation, though, with the 3spd auto, 55 would be 1,942rpm. Based on your 1850 at 55mph data, 80mph would be at 2690rpm. Without adjusting the engine speed governor, you would only be able to get there with your foot touching the floor, even under no load, as the stock governor is a modified constant speed governor.


I don't know what the stock speedometer assumes for revs per mile, but based on your data, it looks like it is closer to 657 revs per mile.