Slipping

[F-450 7.3]

I have a 1999 ford F-450 with a 7.3 in it. Recently my clutch and transmission went out. We replaced the clutch, pressure plate, throw out bearing, pilot bearing, clutch fork, and had the transmission rebuilt. I got it back today and it runs good except for one thing. Reverse, low first, and second are fine. But in third, fourth, and fifth gear if you are at 2500 rpms and and give it all the gas it starts to slip. It does not slip if you just take it easy on the gas when accelerating over 2500 rpms. What could be the problem?????


Thanks for the help.......

 

[BJS]

sounds like there is a problem with the clutch, possibly a greasy hand print on the clutch surface or they didn't clean the shipping oil off the pressure plate.

If you paid a shop to do it then I'd be back at their door and tell them "It's not right fix it now!"

That being said I am going on the basis that you have a stock truck with no power adders, if so then you need a good aftermarket clutch not an OE equivalent.

 

[02stroker]

Could be air in the slave or master cylinder. They are a real pain to get totally bled out on these trucks. It needs to be done off the truck to do it right. The master cylinder does not sit level and allows air to be trapped inside.

 

[DaveBen]

Very true 02stroker. I had to remove mine on a '93 and hand bleed it and then reinstall it.

Dave

 

[BJS]

how would air in the clutch impact slipping if he's not on the clutch. Wouldn't that just make it hard to get the clutch to disengage?

 

[DaveBen]

Sorry, the clutch mechanism is hydraulic operated, just like your brakes. The pedal is connected to the clutch arm via the hydraulic oil in the lines. Bleed them first before you go taking the mechanism off.

Dave

 

[bigrigr]

The hydraulics only aid in releasing the clutch so you can stop or start. The slipping wouldn't be caused by that unless someone or something was keeping the clutch from engaging all the way. ie foot on the pedal, bound up linkage, etc. Sounds like grease on the parts, or a bad pressure plate.

 

[bbressler]

I'm going to say dirty clutch too. I had a fuel leak up top, it ran down onto the flywheel and sure made me think my clutch was going south. Once I got the leak fixed, it took a few good slips to burn that stuff off.

 

[02stroker]

Had a slave cylinder go south on me about a year ago. Truck would drive, but you could bring it to a stop without putting the clutch in. Bleed it out and it was fine for a day, then back to slipping under load. Just a suggestion. Doesn't require tranny removal to check. If you had a shop install the clutch, I'd just take it back and tell them to fix it. Hopoe you get it worked out.

 

[xtrahappy]

Newbie here, adding my 2 cents. See if they might add up. My truck did the same thing, before I changed clutch. It slipped in higher gears, such as passing someone. What we found was flywheel wore down , along with some plate wear.