yea the 4.6 mines been good and i drive it like theres no to morrow, o by the way it doesn't lack speed i've been clocked at 136mph. 06 f-150 super crew

 

damn what tires are u running.. stock ones will fly apart

 

Haahaaa - take a number

 

710 cap wright 710 on a peace of paper and then trun it up side down and read oil

 

I get that. The reason I ask, I am going to change my rear axle so I can do a drum to disc conversion. I wanted to know if you think I should go ahead and upgrade to the 9.75 since I am completely swapping out the rear for disc. You know, kinda an all in one job. Are they a direct bolt on? I read something about having to change the driveshaft if you go up to the 9.75...

Swap for disc, upgrade the rear end and change the gearing. I got a 3.08 8.8 right now and if I'm replacing it, what's the best option for doing so. I'm not sure if the price is going to be that much difference.

I think the 3.73 is more than enough for my normal driving and it's only a 2WD. With the current gears, I am only doing 2K at 78 MPH. If I go up to 3.73 I should still be able to do 70 at or below 2K RPM, right?

 

To make a gear swap worthwhile you should go to at least 4.10s. If you swap to a 9.75 it will bolt up but you will need to shorten the driveshaft. While the 8.8 is still in place remove the driveshaft and measure from the tip of the output shaft at the tranny to the flange at the pinion on the diff. Try to measure from the center or as close to it as possible. This will make for more consistent measurements. When the 9.75 is installed redo the measurements. The difference between the two is how much the driveshaft must be shortened. I measured mine with the wheels on the ground.

JMC

 

HI!... Not sure if it applies to the F-150's or not but on some of the older cars/trucks, when originally eqqiped with rear drum brakes and you convert to rear disc brakes you had to change the master cylinder too.

 

I read that too. I need a new master cylinder anyways, so no biggie. I have to do some more reading to find out what I need to convert the front to Anti-lock. The rear drums are anti-lock now but not sure how it's all going to work together.

I guess I will go with the 9.75, if I can find one instead of the 8.8. I plan on swapping out the 4.6 for a 351 once it dies in my farm truck so the 9.75 should be enough to hold up.

Thanks for the info guys. That confirms what I have researched thusfar.

 

i run the stock tires on it had no problem yet but it does walk the road

 

ya know, my moms 65 mustang lifts the front end off the ground at 130... aint that scary? i wanna see if my big red 4x4 block does the same thing when i get my 5.4 built lol

 

your better off sticking to an 8.8 more upgrades available for it and there is less power loss through the rear end because the gears are smaller. also theres a good bit of weight difference between the two axels. but i thought about going 9.75 but its just to much hassle for little gain.

 

I agree. I will go with the 8.8. Now I'm trying to decide whether I need 4.10 gears with my little 4.6. I want to upgrade the motor later so I want to make sure my suspension and rear will handle it. I'm going to have to do a tranny swap when I drop a built 351 into it.

So for 400rwhp, I think 3.73 would be plenty to handle the TQ but 4.10 may be the better upgrade. I just don't want to lose much of the lower cruising RPM's.

 

id run a 3.90, the 4.6 is a square bore motor so it spins up fairly quicker than a 5.4 people with 5.4's like 4.10's and 4.33's for their so the engine will spin up quicker. but 3.73 or 3.90 would be ur best bet with a 4.6

 

The difference between the 3.73s or 3.90s and the 4.10s on the highway is minimal. If you are serious about the engine swap then I would plan my drivetrain around the 351 not the 4.6. FWIW I would pick a 5.4 with 4.10s over a 4.6 with 3.90s or 3.73s any day of the week. How much torque will the 351 be putting out? The 5.4 makes 350 ftlbs and has a torque converter multiplication of 1.9:1 and the stall is 1830-2130 rpm. Why does the 5.4 come with a 9.75? If your 351 is going to be close to the 5.4 you might want to rethink the 8.8. Remember taller gears are going to multiply the torque.

 

HI!... IMO the 8.8 is junk in the trucks. 31 spline axles compared to the 9.75's 35 spline. The ring & pinnion is larger, but thicker and stronger. The spider gears are twice the size of the ones in the 8.8. The 8.8 was designed for a light MUSTANG, not a heavy 4500-5500LB truck. Just ask JMC, I belive he blew up 3 8.8's before he got smart and switched to the 9.75. He was only making around 300H.P (flywheel) when he broke all those 8.8's. The 9.75 has been proven to withstand upwards of 800RWH.P in stock trim with the LIGHTNING guys. The stock 8.8 in the trucks is only good for about 350-400RWH.P and they break HARD........