I went from 3:55s to 4:10s and love the performance from the gear change but hate the fact that at speeds over 80MPH and under hard acceleration running up the RPMs, my stock aluminum driveshaft (one piece) vibrates something fierce. I've read enough posts where it appears there's no real solution to fix this problem other than to get a driveshaft that's made for higher RPM and lower gears. While at the dealer today, I noticed that the 2003 Harely SC F150 comes stock with a cast iron driveshaft and not the aluminum driveshaft. I image the Harely's driveline is about the same as my ext cab. After that long introduction, here is my question. Has anyone with a "non-aluminum" driveshaft experienced rough vibration coming from the driveshaft after a gear change? I am considering having my driveshaft rebuilt and want to go with the right type.

Thanks in advance for your help.

 

I have 4.56's with 285's. I have the cast driveshaft with no vibrations. I notice on the end of my driveshaft there are 2 balance weights. If your driveshaft is balanced and your universal joints are ok, then the driveshaft was not installed correctly after the pinion install. When the driveshaft is removed from the pinion flange it must be marked and reinstalled in the same o'clock position as it came from the factory. That's about all that can cause driveshaft vibration.

 

Yep, I'm going along with what shrike said. Try changing the orientation of the driveshaft until its reindexed to the factory position. If you can't get it right that way then take it to a driveline shop and have them rebalanced.



Shrike I got a question for you. How does your truck handle with the 285s and 4.56s? I'll be keeping my truck around for a while longer so I'm gonna be regearing. I was going to go with 4.10s with my 285s, but 70% of my driving in that truck now is gonna be towing and I don't think 4.10s are gonna give me enough grunt. I've heard from a couple friends that said they were hitting the rev limiter with 4.56s and 285s while towing (dunno if they were using OD or D). Sorry for the temporary thread hijacking.

 

I think 4.56 is the way to go. I don't tow and I'm so glad I didn't waste the money on the job with 4.10's. Everyone I talked to about the install said I was nuts, but after the mechanic completed the job and drove it he was really suprised how mild it was. We both think it acts like a 3.73. I will keep it in D to about 70 mph 3.2k rpm's then hit OD and drop to about 2300. If you don't lock out OD it will shift much sooner. I feel like I added 2 cylinders to the motor. My MPG is better and my trans runs cooler. The only thing I guess you could say is a drawback is the noise. It's not really loud, just noticeable when decelerating. The locker gets louder than the gears though, it sounds like a baseball card in a bike rim. But I don't mind one bit...

 

And Powerstroke, you saved my *** when I was ordering everything for the job from randy's. They told me I needed a Dana 44 R front end and you brought the 8.8 IFS to my attention. Thanks Alot!

 

You know now that you mention it, I kinda remember being one of the people saying you were nuts for going to 4.56s with 285s (or were you going with 265s at the time?). I remember you asking about what Randys said. Normally they're on top of the game. Its possible they thought you had a 96 or something. From the sounds of this is probably what I'll end up going to. I'd go back to the stock tires, but I've got the body lift and it was such a pita to put in I'm not taking it out, so the 285s I've got laying around are goin on. Since I'm gonna be pulling a trailer that weighs over 1000lb plus a Ranger and misc parts and tools it will need some power. The noise you're talking about, other than the locker noise (mines gonna stay open anyhow) are you talking about engine noise or gear whine? If you have a Superchips microtuner you can change all the shift points to maximize the gears.