My 93 cummins 5 spd with 4:10 rear gears when I'm shifting to 4th from 3rd on a hill unloaded the truck seems lugs its fine on flats and downhills. The only way it doesn't lug is by staying in 3rd on the throttle until the revs seem to stop rising and push it a little more then shift like 30-35 mph. So my question is is it bad to run the gear out that much there is still power but the engine just sounds like its revving pretty good.

 

The gap in gears between 3 and 4 is rather large. If your truck is not modded it wont hurt to run it up against the governor like you have been doing. I do it all the time pulling. Fill out your sig so we can help you better.

 

Installing a 3,200 rpm '366' governor spring will help with this problem.

 

Also, and for free, check to make sure you are getting the full amount of throttle travel that is available. There are instructions in the sticky (at the top of the page) for moving the linkage and adjusting the high speed stop.

I have a 5 speed/4:10 combo and before the I installed the 366 spring it would still go about 45 in 3rd with just those things above.

 

The full throttle stop is the ONLY pump modification I made on my old carhauler, which is running a Non-intercooled 1990 Cummins, 4.56 gears and an NV4500.
Removing the full throttle stop made a night and day difference with the top speed of the behemoth.
It went from a 65mph, solidly mashed to the floor, to a top speed on flat ground of as high as 78mph, JUST with removing that part and re-adjusting the linkages accordingly.

It was a totally different truck after 5 minutes of adjustments.

Mark.

 

I too had concerns when I first got my 12 valve about how hard one could twist the ears off it before shifting. I think that is his concern. Needs reassurance that if the motor is solid and well maintained it will take the abuse of twisting it until it wont twist no more.

 

Well with 3.54's my 3rd to 4th shift is even worse then 4.10's. Put the 366 spring in made a HUGE difference. As well as adjusting the throttle stops and linkage.

If I'm pulling and need to make the 3 to 4 shift I will buzz it up to around 2500-2600, then shift. These motors were designed to run at full tilt..2500 rpm all day long. SO buzzing it up to the stock Governor RPM won't hurt anything.

 

I have 60lb valve springs. And I've known this engine since the day it came off the showroom and with my 366 spring i will wind mine up sometimes to the 3400 area before shifting to 4th on a hill loaded. And usually if I need to get up and go while towing I'll run first second and third out to 3200. And cruising down the highway because I will NOT tow in fifth gear I'll run 2400 to 2700 for miles. Engine still sounds like new. I wouldn't worry about yours too much

 

As said, just back the full throttle screw out.

 

Thanks everyone for the help. So pretty much I'm not hurting anything but if I want to get rid of the issue I should back the throttle screw out and get a 3200 rpm gov spring.

 

Well you'll never eliminate the issue...since its the actual gearing in the transmission that is the real problem. But you can make it so it's a lot easier to live with.