Hello im back, I need some advice and help on how to properly shift these old trucks. I think I finally have the double clutching down now, but I was just wondering if it hurts anything to shift down with the transmission in 4th gear and the rear end in high speed. Would it hurt to down all the gears expect 1st in high gear on the rear end; or is there some other more correct way of doing it?? I really dont want to have to find another rear end for this truck. Btw it is a vacuum two speed to. Thank you all for your help and have a great day!!

 

Unless you are hauling heavy loads, I would put the rear in high range and leave it there. Then just shift it like a normal 4 speed. These old trucks are slow enough as it is.

If you need to use low range, (split shifting) that is another challenge all together......Someone else can probably explain it better than me.

 

Hi - This is not really easy to explain but will try. It will not hurt anything to shift the trans without shifting the rear end, after all it is the same as if you had a single speed rear end. By split shifting you do not have to rev the engine as high when down shifting and won,t lug the engine as much when up shifting. Hope this helps.

 

Ok thank you for all of the help. So at least I know now that I can put in high and then safely shift without hurting anything. Should I shift from high range down to low range after I put the transmission in 2nd before I completely stop at a stop sign, and start in 2 low and go to 2 high after I stop at a stop sign?? Thank you again for all of your help and have a great day!

 

Hi again I personally would shift into low range after stopping. When empty I would leave it in low until you are in forth then shift into high range. Vacume shifts are fairly slow so they need time to do their thing so the extra speed will help while waiting for shift to take place. You should be able to hold the throttle under load, move switch to high range then ease off on the throttle and it should shift to high. Believe it or not the diff shifts better when truck is loaded as the extra weight helps to keep momentum.
Just a tid bit. 5 spd. trans with Eaton 3 spd. tandem diffs were used in Ford (and other makes) C - Series tilt cabs. I have also seen IH conv. with this set up but have never drove any. I did however drive a Western Star with a 13 spd. and 2 spd. tandem diffs.

 

thank you for your help old ugly. I had no clue on how to properly shift these old trucks, so any tips or suggestions I can get are very helpful. Now just one more thing, when I have weight on my truck should I leave it in high range until I stop or shift from 4th high into 3rd then to 3rd etc.? Then to start I would start out again in low range from and go on from there.
Thank you again for your help

 

We had both the electric and vacuum shift. Since as noted, the vacuum shift may be a slower shift, you'll have to get the feel for it before you try split shifting.

Usually, you can just shift 2-3-4 and use high range as a "5th gear".

When you reach your desired shift point, pull the switch up or out if dash mounted, and release the throttle. You will feel the shift. Back on the gas and away you go. Don't use the clutch.

Now, you are running along in 4-hi and you hit a bit of a hill. UNDER LOAD, with the throttle DOWN, push the switch down or in. Then, holding the throttle, stab the clutch. You should get a pretty quick shift and your revs will run up to match your new driveshaft speed.

SPLIT SHIFTS:

Going up through the gears: Start in 2 lo. Shift to 2 hi as above--hold the throttle, shift, lift throttle, feel the shift, back on the gas.

2 hi to 3 lo: Keeping the two speed shifter in hi, shift from 2nd to 3rd. Once you are in 3rd, push the two speed shifter down or in. This is going to be hard to do with a dash mounted shifter, so think about this--you don't want to go in the ditch while fumbling for the two speed shifter.

3lo to 3 hi: Same as above. 3 hi to 4 lo, same.

Down shifts MUST be done under load or at rest. You CAN NOT downshift the axle like the trans--say you are going down a hill and need extra engine braking--NEVER shift the two speed from hi to lo in that circumstance. It won't shift and you will have no engine braking, and may have it engage with a bang.

The Eaton instructions are on line. If I find them again, I'll post a link. They are very insistant that the two speed be in "HI" whenever the shifter is moved.

As such, I would avoid splitting downshifts, unless I was going UP a hill.

 

OK, scroll down here for the Eaton instructions. Note comments from people (including myself) who have or have seen two speeds shifted any old way. Don't try that with yours:

https://www.ford-trucks.com/forums/1...-problems.html

 

Wow, thank you for the help, those videos along with what you all have said have cleared up and answered a lot of questions. I will try these techniques tomorrow and hope I have better luck, so maybe no more grinding. Thank you all again for your time and help!!! Have a great day!!!

 

[quote=tinman52;10468676]Unless you are hauling heavy loads, I would put the rear in high range and leave it there. Then just shift it like a normal 4 speed. These old trucks are slow enough as it is.

Hello tinman52, got a couple questions about 2 speed diff. that no one responded to yesterday, can you help? Thanks https://www.ford-trucks.com/forums/1...questions.html

 

I was just wondering if I can just change my gear ratio on my 51 ford f-6 so I can go faster then 40 mph I'm new to here so I don't even know if I'm doing this right but I need help I have the split rear end

 

Welcome to FTE! Show us photos of your truck, we like pictures! If your axle is 5.83 in high range, you shouldn't have any trouble running 55mph.
Mark