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1991 f-Superduty shifting problem


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LOSTbutAMBITIOUS
User

Mar 3, 2010, 11:03 PM

Post #1 of 15 (2915 views)
1991 f-Superduty shifting problem Sign In

I just bought a 1991 Ford F-Superduty(reads F-450) 7.3L diesel. I realized it would need work when I bought it, now I'm just trying to figure out what work and how much that work is going to end up hurting my wallet. Very difficult to shift into 1st, 2nd, and reverse. 3rd 4th and 5th shift fairly smoothly. Situation pretty much the same moving or stopped. Any idea what's going on?


Tom Greenleaf
Ultimate Carjunky / Moderator
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Mar 4, 2010, 2:07 AM

Post #2 of 15 (2911 views)
Re: 1991 f-Superduty shifting problem Sign In

A guess: F-450! Wouldn't fit in my whole area! No matter - if this uses an hydraulic clutch linkage it may not be fully disengaging due to a leak, low fluid (clutch master cylinder) or any hydraulic leak in that if that type.

A clue that clutch isn't disengaging properly/fully would be that it would probably shift fine with engine off,

T



LOSTbutAMBITIOUS
User

Mar 4, 2010, 8:39 AM

Post #3 of 15 (2903 views)
Re: 1991 f-Superduty shifting problem Sign In

Okay. I was told that the slave cylinder was just replaced, I checked the fluid level on the master resevior, it was good. So try replacing the Master Cylinder?


Tom Greenleaf
Ultimate Carjunky / Moderator
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Mar 4, 2010, 8:59 AM

Post #4 of 15 (2901 views)
Re: 1991 f-Superduty shifting problem Sign In

Not yet! It may need to be bled better or again - can't say. The symptoms are consistent with the clutch not fully disengaged but that's not certain yet.

Try shifting with engine off as mentioned earlier. Just pretend engine is running. Reverse is usually unsynchronized and may not go there on first try - alone could be normal.

While running at idle, if you went for reverse with clutch pegged to the floor, moving shifter slowly there could be a "ZIP" of gear sound going into reverse and don't go further if that does that. Transmissions that are shifted quickly from neutral can do that as there isn't time for shaft to stop. Put in a syncroed gear first will stop the gears for easier meshing.

If slave cylinder is still in the cards, it should or hope you can see lack of enough motion from the clutch pedal to disengage clutch.

Out there for similar symptoms could include corroded or warped clutch or clutch related faults,

T



LOSTbutAMBITIOUS
User

Mar 4, 2010, 9:17 AM

Post #5 of 15 (2895 views)
Re: 1991 f-Superduty shifting problem Sign In

It all shifts smooth as butter with the engine off. I'll try bleeding.


Tom Greenleaf
Ultimate Carjunky / Moderator
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Mar 4, 2010, 9:26 AM

Post #6 of 15 (2892 views)
Re: 1991 f-Superduty shifting problem Sign In

Go for it and pls let us know how it works out,

T



LOSTbutAMBITIOUS
User

Mar 7, 2010, 8:12 PM

Post #7 of 15 (2869 views)
Re: 1991 f-Superduty shifting problem Sign In

Okay, I bled the system (I did it so the quality of workmanship is pretty low on the scale) and replaced the master cylinder. I don't think there's any pressure in the system (a leak? or defective master? bad job bleeding and still has air?) the clutch is just really 'loose'.


Tom Greenleaf
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Mar 8, 2010, 3:38 AM

Post #8 of 15 (2863 views)
Re: 1991 f-Superduty shifting problem Sign In

Unless you are incredible with a camera you are my eyes here! Some hydraulic linkages are a total pill to bleed out. Not sure how you are doing this - gravity bleeding probably won't suffice. Two people if you don't have a pressure bleeder device required and correct procedures.

Note: If capturing fluid (usually brake fluid, DOT 3) don't re-use bled off fluid!

Person in vehicle pushes clutch to floor a couple times and holds it there. You then quickly open bleeder at the slave cylinder and shut it when flow slows. Now person in vehicle can pump clutch again and repeat while watching that the little master cylinder never gets too low keep doing this till no more bubbles are seen. Watch action as the slave should be pushing on a pivot fork of some creation which pushes the throwout bearing against pressure plate for full disengagement.

Some of these are such a pill you need a forced bleeding device as air naturally floats is doesn't always push and purger out going down to that slave cylinder easily or without trickery, lots of shouting and tools that suddenly become projectiles!

There may be adjustments at pedal, or perhaps slave cylinder?? Have to look. If so on a monster truck my guess is the aim would be for about an inch of pedal free-play at top, then it begins to press hard to disengage clutch. Must be some free-play but not too much.

Your eyes need to see that the pedal, pivots under the dash and all aren't screwed up which I think would be rare but who knows - old truck and probably made to work hard and did and will again,

T

PS: Master cylinders are bench bled before installing and instructions should have been included for that. If not done it can make a bigger headache of bleeding this. It may be able to do on vehicle with a line from exit port made to return fluid to reservoir, then quickly re-attach line and start this over.



LOSTbutAMBITIOUS
User

Mar 8, 2010, 10:12 AM

Post #9 of 15 (2854 views)
Re: 1991 f-Superduty shifting problem Sign In

LOL. The hits just keep on coming! That's not how I did it, so I'll try next. Once I get my new problem fixed: I seem to be losing prime in the fuel pump overnight. I can't see any fuel leaks, so I have no clue where to start. Any suggestions on 1st, 2nd, 3rd culprits etc.? Should I to start a new thread for this problem?


(This post was edited by LOSTbutAMBITIOUS on Mar 8, 2010, 10:29 AM)


Tom Greenleaf
Ultimate Carjunky / Moderator
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Mar 8, 2010, 10:38 AM

Post #10 of 15 (2850 views)
Re: 1991 f-Superduty shifting problem Sign In

Get the clutch fixed first but keep an eye out for gas smell in oil for the "losing prime" as you put it for fuel. If injectors leaked down it would foul the next start with gas and oil level might be too full - that would be an emergency to fix.

In the mean time - Just put key to "run" for a few seconds before asking (turning) to starter motor may be enough for now and indefinitely. If that doesn't do it start a thread just for that issue which will help get others with ideas involved,

T



LOSTbutAMBITIOUS
User

Mar 8, 2010, 10:46 AM

Post #11 of 15 (2846 views)
Re: 1991 f-Superduty shifting problem Sign In

I'll start a new thread, I already have to turn the key to on and leave it for about ten seconds (glowplugs) but, i'll keep at the clutch when I can find a second person to help.


Tom Greenleaf
Ultimate Carjunky / Moderator
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Mar 8, 2010, 2:16 PM

Post #12 of 15 (2843 views)
Re: 1991 f-Superduty shifting problem Sign In

OOPS! Forgot it was a diesel! That changes the cold starting thing of course. I'll look for the other thread. Some of the other guys here may be tons better with the specific dielsel issues,

T



LOSTbutAMBITIOUS
User

Mar 12, 2010, 3:57 PM

Post #13 of 15 (2825 views)
Re: 1991 f-Superduty shifting problem Sign In

Looks like the clutch's problem is the pressure plate.


Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Mar 12, 2010, 4:09 PM

Post #14 of 15 (2822 views)
Re: 1991 f-Superduty shifting problem Sign In

Not sure how you came to that conclusion but you are there and I'm not so be it. I do suggest if you are going in to replace it to just do the disc and throwout bearing while there.

Important: Don't let trans hang any weight on disc of clutch with its input shaft as that can warp the disc and cause this issue right from new all over again! Support trans till a couple bolts are tight and that won't happen,

T



LOSTbutAMBITIOUS
User

Mar 14, 2010, 12:49 AM

Post #15 of 15 (2816 views)
Re: 1991 f-Superduty shifting problem Sign In

10-4. Thank you.






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