Ok, you guys have always been a big help so I'm hoping ya'll can help this TX gal more than anyone here in TX has been able to. My truck has been doing this really weird thing. It's hard to explain but here goes.... I pull up to a stop and it's got a clunk type sound. Sometimes it does it when I stop and sometimes it doesn't. Then different side of the same coin, sometimes on take off, it has the clunk sound. This truck has NO power for jumping the line so It's not like I'm cramming the gas pedal or anything. It's a 79 F100.

Also, and it may not be related at all but it seems to me it would be. When it's been parked for a while, like more than an hour, and I put it into either reverse or drive, it's sluggish to take off. It's like it's stiff and doesn't want to move and if you gas it, you can feel it like something was freeing up and then it'll just slide like nothing. It doesn't jerk to free up, it just starts moving lots easier. It doesn't matter what gear but it has to be setting for a coupla hours or more before it does that. Could that be the brakes too or would that be something else?

Thanks ahead of time for any ideas!
Connie (only Ford luvr in the family!)

'79 f100 "Silver Ghost" (my baby)
'83 f100 "The Ford" (my first)
'85 f150 "Old Blue" (my next project)

 

If the sticking problem happens all the time, I would let it sit for and hour, and then jack each wheel up and turn them by hand to see if you can find which one is sticking. I would imagine the clunking is coming from the suspension where the brake is sticking. The wheel is locked so it won't turn, so this is probably making the axle twist and giving you the clunking sound. If you find all the wheels locked, then I would suspect something wrong with the master cylinder or the pedal rod adjustment.

 

Otherwise, it it could be front calipers not allowing the piston to return or rear brake hardware not pulling the shoes back.


[font color=red]Dennis

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[font color=blue]78 F-150 429CJ,Silver,Explorer Pkg.
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one of the calipers coould be frozen

 

i also say front caliper might be seazing up. i have the same problem. that will be fixed this weekend hopefully. it's not seized badly yet. it just sticks a little. try a little WD-40 inside the rubber boot. my dad did that and it worked for a while

 

Ok, well, when I bought it, the master cylinder was bad. I had just replaced the one on my 85 that I wrecked and it was only a coupla months old and they were the same so I just swapped them and then had to bleed 'em of course and alla that jazz. I'll try the turn it by hand thing and see if I can tell anything by that. I have to pull the wheels off and wash behind them anyway becuz I got into some massively deep mud two days ago and It's caked into everything. That's what I get for helping a friend....LOL. Once I get everything cleaned up and actually get down there to see things maybe I can tell. Thanks for the ideas!

Connie (only Ford luvr in the family!)

'79 f100 "Silver Ghost" (my baby)
'83 f100 "The Ford" (my first)
'85 f150 "Old Blue" (my next project)

 

I would also suggest checking the brake calipers. I have had this problem before on a different vehicle. Same symptoms. One of my calipers was sticking. Replaced it and it went away.
Good Luck

The wiggler

'76 F100 flareside

 

 

I had a similar problem on my 77 recently. I had one brake locking up periodically, and it felt like it was one of the rears. When I pulled the drums, I found that one was acting erratically. On the side opposite, I had an axle seal leaking, which was contributing to the erratic operation. Just something to consider.

Jason

1993 F-150 300 I-6 5-Spd.
1977 F-250 351M 4-Spd.

 

Connie,
Your assumption is normal and the replies are as expected.
You own an old 1/2 ton truck. Your leaf springs are worn out.
As you brake you are creating a rotational force on the rear end. It is driving the differential(rear end) nose down and this is pulling the driveshaft out of your tranny or off the splined of the two piece shaft. The spline of the two piece driveshaft is more likely because the truck would be heavier and more likely to wear out the springs. The spline would also be more likely to be unlubed which would cause the drive shaft to bind and clunk as it broke loose and slid to the end of the spline. The driveshaft is out of alignment at this point and as you accelerated you are driving the nose of the differential up and pushing the driveshaft back onto the spline. After the motor creates enough torgue it breaks the driveshaft loose and it slams back up on the spline. This causes not only a loud CLUNK but makes the vehicle jump a little.
Whew! That's one hell of an explanation!
Solution: Add a couple of leaf springs from the junk yard and lube your spline. You'll be good to go!!!!
My Way is the Highway,
KingFisher