Hey guys, I am still pretty new to the diesel truck world but I have been working on a project for about the last 4 months now and finally got to drive the truck for the first time last week. I took it on a road test yesterday and found that I may have some super low gearing in my truck. I don't have a speedo that works yet but the best I can tell I was only doing about 35 mph and the truck was literally screaming at me. The frame is an 85 f-250 and my question is, is this typical for the 4 speed or should I change my gears in my rear end? I don't know if its a granny low truck but it seems as if all of my gears are really short as well. Any info would help. Thx in advance.
Shawn

 

You should be running somewhere around ~2200RPM @ 60MPH.
The 4-speed should be in front of 3.55 gearing, but if it is indeed running that fast, you may have it in front of something else.

Um... Is your truck a 4x4? Could it be in 4x4 low? If the front hubs are not locked in, the transfer case will just spin the front driveshaft and you'll still only be powering the rear tires, but it will be a *lot* lower geared.

 

must be in 4lo.even the 5.13 gearing don't make her scream....until at least 55 lol.

 

It does seem like its stuck in 4-lo, but I can move the transfer case between its gears. Any chance its in 4-lo even though I have the t-case 2-high. Maybe its stuck? Are you saying that I can put the truck in gear and if its stuck in 4-lo, the drive shaft to the front axle will spin? I will check that out tomorrow morning.

 

If the transfer case is stuck in gear, whats the best way to get it unstuck?

 

Yes, the front drive shaft will spin. Alternately, if you have the hubs unlocked, you can try to rotate the driveshaft by hand -- if it rotates, you're definitely not in a 4x4 gear.

 

Does anyone happen to know the lever position pattern by chance? I have tried to search google, but I am coming up with mixed pictures of 4 low being the most forward position which is where I assumed 2 high would be. In the pic I looked at the 2 hi position is the third position from the firewall. Does this sound correct? I will be leaving work soon and before I go to bed I will find out for sure. It may just be an issue of my lever being in the wrong spot. That would make me feel like a dumba$$. LOL

 

Forward is 2HI, next is 4HI, then neutral, and all the way back is 4LO.

 

i tried it this morning. All the way forward is 2 hi. I thought I had something going there so after that was a bust, I crawled up under the truck to look at the tag on the rear end and someone took it off and the hog head has black silicon coming out of it. That tells me that the gears were more than likely changed. Thx for yalls help.

 

Pull the diff cover, the ratio should be stamped on the ring gear, or you can just count the teeth. Ring teeth divided by pinion teeth = gear ratio

 

There will be a very obvious difference in feel between 2 or 4hi and 4low. If you shift between the four positions and there is no difference, there's a good chance your linkage could be the issue (or something inside the t-case).

To find the gear ratio, just jack up the axle, put it in neutral and count how many times the wheel rotates vs the pinion.