1995 F-150 XLT Short Bed, Black / Silver two tone Trailer Towing with 3.55's with a tall black capper.
180K and owned by me since 1998 with 16K, two owners.
5.0l stock innards with K&N, Tricked Jacob's Mileage Master ignition system incorporating the coil trigger from an older Jacob's unit so I have two complete ignition systems by swapping the coil wire location.
Shorty headers through the original Cat to a stainless catback exhaust. All ECU sensors are new as are water pump, thermostat and 14 lbs cap , 130 amp alt, MSD Super Conductor Ign wires with heat boots. 14 btdc and Motorcraft copper cores one step colder and side gapped to .55 . '98 explorer 4 hole injectors. I have taken this rig from 12 ->14 mpg to 18 city and 22+ highway.

Diagnosing a noise:

Pulling away from a stop you hear/feel a short groan popping sound which is low frequency and repeatable rolling on and off the throttle. brake application doesn't reproduce it.

I originally thought a combo of tired motor mounts and transmission cross member mount. They look structurally intact but will get changed soon.

A local shop mechanic that grew up working in a Ford Dealership shop thinks that large rivets mounting the cross member to the frame rails (or someplace) have worked loose, he said it was typical at this age.

My question being, if this does pan out to be the case, doesn't it make sense to support the frame with the weight off of the suspension then just weld up these areas secured by the rivets?

TIA

 

I'd be inclined to say "tired" mounts first, then the frame but that would depend on what sort of work the truck has been doing (loading, terrain, torque (flex), etc) --- the frames on these trucks are relatively "thin" compared to the F-250/350s

 

90% + highway and DD with occasional (rare) 3000 lbs +or- towing. Off road to fish and hunt or going parking with a local hooker.

 

I assume you have already ruled out u-joints?

 

Not entirely, anything is a possible. That has a ring to it thought. This morning when the whole truck was cold it does nothing. A couple of miles down the road it starts and I don't mean gradually. As if colder thick grease halts the slop and as soon as it warms up it starts talking to me. Good idea, thanks!

 

Another vote for driveshaft u-joints, you will need to disconnect it to really see/feel if any of them are bad.. though if you go that far you may as well replace them as they aren't expensive.

 

Never mind...

 

If it is the rivets, I'm inclined to think it would be better to drill them out (carefully) and put in some grade 8 bolts, rather than welding on the frame.

 

Never mind here too. LOL! My bad.

 

OK feel free to disregard, but doesn't a 4x4 have a 2 piece rear shaft too? If so I think 180K carrier bearing might need a look at as well as the 3 U-joints.

 

You can check u joints without removing the driveshaft, but the drivetrain has to be unloaded. I.e. in neutral with the wheels chocked.