Hey guys,
its been a while since I last posted, but been freqently reading other posts. I have 2 questions/problems for you gurus out there. First of all I have a 94 Bronco 5.0, E4OD, 99K miles.

My first problem is that atfer I had a 4" Rancho lift installed 3 weeks ago, I get a slight vibrating feel and a vibrting sound when on the freeway between 60 and 70 MPH only when accelerating. If I let off the gas,it goes away. Never did it before the lift.

Second problem. After a 150 mile drive today which included a few steep hills, and after the truck sat for a few hours, when i started driving it again, it jumps when the auto tranny shifts gears. It did it all the way home, another 150 miles. It never done this before. I had the pan dropped and changed the fluid and filter about 20k miles ago. Could this be a problem because I just put on bigger wheels and tire (285/75/16, equiv to 33" tall) and still have the stock gearing, 3.55 (going to change to 4.10 soon). The truck was struggling going up those hills as i was flooring it and it wouln't go faster that 65mph. Maybe I over worked the tranny. (this is my main problem since it may cost a lot to fix) This really annoys me evertime it switches gears. Scared it might just give out.

Thanks in advance for allthe help

 

Oh and another thing i found out this morning. It jumps/kicks harder when cold. Please help me out fellas

 

I had a similar vibration problem last year. I had a U-joint going out. With the lift on your truck you will be putting more strain on those u-joints. I would start there.

 

Sounds like you need a longer rear shaft.
Pull boot off of shaft and look at how much spline is left.
When you lift a truck you reduce the amount of spline the rear shaft has.

 

the bronco can take a 6" lift and still have plenty of rear shaft length if the spacer is used, most likely you have a u-joint about to die. do you hear any sort of clicking? and did you get an alignment and have the tires balanced?

my bronco was lifted exactly like yours and I never seemed to have any power issues, but that is probably because the motor was a mustang h.o.(i could smoke the 33" tires easily), if your motor is a little old, the regearing might be just what the doctor ordered to save your tranny

 

it may be a fouled trac bar bushing? i/a

 

Regear! And yes, you could be slightly overheating the tranny or at least the fluid on long trips with the increased RPM's you are turning to achieve the same speeds. Take a look at the fluid now...if its getting dark or feels thin (low viscosity) then thats where your problem lies. Could well be the source of the vibration as well since the tranny relies on hydraulic pressure that can be lost due to loss of oil viscosity. Poor pressure causes slipping and poor hydraulic actuator response internally. The vibration only during acceleration would tend uphold this theory in that even though the RPM's have increased, hydraulic pressure doesn't but under no load the pressure isn't as vital so no noticable problem. A long answer but the short one I'll reiterate...regear.

 

I'd tend to agree with greystreak. The only other thing I would suggest as preemptive is when you do regear change your ujoints also. Not that the two problems are related just that its an easy fix and well its laid up you can kill two birds with one stone.