Gears and driveshaft

[MTCFORUM]

I would like to put a set of different gears in my truck (maybe an 8.8 with 4.10s and limited slip). I am new to this soild axle thing, my T-bird has good old IRS, and not really sure how to proceed. In my T-Bird I was able to simply pull out the old open 7.5 diff. housing, and swap in a new fully complete FRPP diff. with trac loc 8.8/3.73's. However with my truck I am not quite sure how to go about changing things over. Someone will likely have to educate me up a bit here. Thanks again!

[MTCFORUM]

Oh ya, and does anyone no of a place I could get an upgraded driveshaft to go with a new set of gears.

[MTCFORUM]

You have to pull the gearset out. You could then have it rebuilt, rebuild it yourself (be careful there) or even get a 2nd set to just swap in. The 8.8 is a clip axle, so you may need to pull the clips and slip the axle ends out the sides of the tubes, I'm not 100% sure.

As far as a driveshaft, Dynotech who Dennis uses to make shafts for the tbirds, cats, etc could make you a metal matrix, you just have to give them the measurements from your old one.

good luck,
Scott

[MTCFORUM]

Thanks for the info. I am going to check this out a bit more. I have heard that Eaton is the way to go for gears ect... I will have to call around and check prices ect..., anybody have any experience swapping gears in their f150?

I think it would help the truck's performance out a bit. My 3.8L N/A bird with 3.73's in it , feels quicker (more torque) than my 4.2L truck. Gotta love that seat of the pants dyno of mine (joke).

[MTCFORUM]

I don't know about where you live, but around here it isn't hard to find a shop that'll do a custom driveshaft for you. But you may not need it. The main reason for upgrading the driveshaft in the Marks (and i'm assuming the birds too) was to avoid vibration. Depending on your truck, you may not have a vibration problem, so you may not need a driveshaft.

[MTCFORUM]

Thanks for the info. I have been talking to a few people over at fordtruckworld.com and they saw there experiences with new gears, result in a large driveshaft vibration in the vehicle. Good idea about checking around here for someone to make a custom driveshaft for me. I do not believe, unfortunately, in my small city there is anywhere that does this type of thing, but then again I have never asked around before, I will have to check this out.

[MTCFORUM]

I switched the gears in my 97 F150 w/ 4.6 from 3.55 to 4.30 ratio and it made a dramatic difference in performance. 4.30 ratio might be a little steep for a daily driver my high way RPMs are 2k @ 60MPH, 2,500 @ 70 RPMs, 3,000 RPMs @ 80 MPH all on 29 inch tires (wrangler AP 255/70/16).

I used Precision gears and they whine a little bit betwen 35 & 40 MPH. I also have a vibration around 80 mph but only if I am accelerating quickly to that speed. If I accelerate slowly to that speed or cruise constantly at that speed then there is no vibration. I could'nt tell you about any speed over 80 MPH as my speed limiter kicks in at that speed whereas it would kick in at 97MPH with the 3.55 ratio. Need to get the aluminum driveshaft balanced or maybe a new one built for higher RPMS but the 12 point bolts on the pinion flange are a mother to get loose. Once I resolve the vibration issue I'll get the speed limiter eliminated.

I would recomend the 4.10 ratio to anyone as it is the best all around ratio IMO. I'll eventually go to 33 inch tires and dont do a lot of highway driving so I can live w/ the 4.30s for now. I'ts a nice mod that you really feel but there's always the possibility of vibrations to consider and high way mileage might suffer a bit, also you'll need to recalibrate the speedometer. BTW if you dont have a limited slip you might consider doing that at the same time.

Good luck.