williams37

Hi, New to this site, but not forums. I have done a search on here and other f150 sites, but still wanted to post specifically about my problem. I just bought a 98 F150 4.6l 5speed manual with 4x4. This engine/tranny combo is either extremely rare, Or I am just the only one with issues.

My problem is when I take off from a start in 1st gear, I get rear end shudder pretty bad until about 15 mph. It does this ever so slightly from 2nd gear starts, But once Im moving 1st gear acts completely normal. I am the only the 2nd owner of this truck and it was immaculately taken care of by the original owner, I do however believe that it is the original clutch. With 123k I am curious if this sounds like a clutch issue or a rear end issue.

Things I have tried to isolate the problem and diagnose are...
Added clutch fluid - helped tone down the shutter by a very slight amount
Tried seeing how it acted in 4x4 - no shudder whatsoever. Drove normal
2nd gear starts low rpms - Not a fan of lugging a motor or burning clutches, but this seems to eliminate the rear end shudder 95% of the time.

Its a lot to read through, but I do love this truck, Just wish it drove like my 01 v6 5 speed. Any help would be very much appreciated!

And here it is!

Silverbulet

By shudder what do you mean? Is the truck shaking when you let out on the clutch? You may be experiencing clutch chatter.

bobkyle2

Does it have a locker in the rear?

Have you check your trans mount? Or even Engine mounts?

greenheadkiller98

Its probably time for new clutch packs if you have a limited slip rear end

williams37

I'll try to crawl under the truck and find out some of those questions ( only 7 degrees here today) but by shudder, I mean the rear end has a violent bounce where it literally feels like the rear tires are trying to hop off the ground.

williams37

Yes, the issue is only while releasing the clutch. I have tried different speeds of releasing the clutch, but it seems only noticeable in 1st gear. I doubt it's an actual issue with first gear, because it is completely fine after the clutch is completely released.

95FordMN

Sounds like a rear dif issue, and it looks like you have the off road package and therefore a limited slip rear-end. Problem time to change the rear dif fluid but judging by the severity of the issue it sounds like some more intensive rear end work might be necessary

williams37

Unfortunately, That is the case. I just picked up the ford friction modifier and had Valvoline change the rear dif fluid after adding the modifier. He said he sucked out enough oil shavings to clog his machine four times. The issue remains, but I expected it to after hearing about how ground down my gears are. I don't have any experience with rear ends, but I guess its time to start exploring my options.

Triton-SAS

Definitely time for new gears or a used rear. My shakes in reverse due to my locker. 14 bolt but same concept.