Hey everyone,

I've got a 1990 Ford F150 XLT Lariat with a solid axle swap from a 1978 Ford Bronco. Every part in the front end is brand new, except the axles. Every part of the steering is brand new. My transfer case is a BW1356 and is completely rebuilt with all brand new internals. My Transmission is the E40D from a 95 bronco and is completely rebuilt with all new internals and gaskets. The only thing that I did NOT have built or custom made was the front driveshaft. The front driveshaft was out of another OBS f150(but has all new u-joints). Also new is, I've never owned an OBS F150 4x4 before (this was a 2WD truck that I did a complete build and swap into. Also, this noise/vibration does not exist in 2 wheel drive.

So, today is the first time I've been able to use four wheel drive in the truck because of the deep snow. I'm noticing a growl (or slight vibration) coming from under my feet upon deceleration in 4 wheel drive high. Now, it doesn't happen at all speeds, and it doesn't happen while accelerating. It seems to happen if I'm decelerating from speeds above 35mph. I can stop the noise almost immediately as soon as I get on the gas. Almost feels like getting on the gas takes the slack out of "something". Once I get under 30mph, deceleration no longer produces a noise.

It almost feels like it's the front driveshaft. Not sure. Thoughts?

Thanks!

 

I found a video that shows the noise I think I'm hearing from the front end . You can hear it when he gets off the gas.

 

Have you checked your front driveline angles? If you have a double cardan u joint the pinion should be pointed at the transfer case yoke. If you have a typical u joint the pinion should be parallel to the transfer case yoke. If you stray too many degrees from ideal the joints can get noisy. There’s a pretty good Tremec driveline angle app that you can use to measure your angles with your phone and confirm they’re happy. Apologies if you’re already aware of all this but that’d be the first thing I’d look at.

 

Did you get new gears and bearings in the front axle?. You may be sucking the pinion into the ring gear . It pushes apart under acceleration and draws together during deceleration.

 

Thanks, I'll check that out. I've worked with pinion angles in rear-wheel drive applications, but this is my time dealing with a setup that has a front drive shaft.

The dana 44 from the 78 bronco has all brand new internals, including a yukon zip locker 4.10's.

 

Sounds good. Also be aware that even if the angles are in spec with each other there’s still some limit obviously on how much an angle the joint will tolerate. As-in even if your pinion and tcase are parallel they still only tolerate a Max u joint angle. I think spicer lists that max angle somewhere. Once you reach that you need to go with a double cardan shaft and adjust your pinion angle accordingly.