i finally decided to change my rearend. im thinking of 4:30's. the truck 1999 4.2 single cab shortbox. stock tires 3-3 drop. am i going to kill my top end? my truck shifts out of 2 at 77mph. i dont think i will kill my top end at all . all im asking is 100mph . i do not want to turn over 3000 at 70-75 because i drive 8 miles on the interstate. i would go 4:10 but i want it jump off the line!!! do yall think there would be any chance of being able to spin em off the line. if not , not a prob the 100hp shot of nos will take care of that. oh yeah it is an auto with 3:55 thanks to everyone on this board that ever helped anybody, alot of us would be lost without the help

 

I think that you should go with 4:10's. They offer a nice blend of torque, and you would be supprised with the difference that it will offer. You can still take it up around 100 no problem (not that you'd be going that fast, right? ). But, don't forget... with either change, you'd have to change your spedo gears. Hope this helps.

-Flea

 

are no speedo gears in a 99. you will have to get a aftermarket chip burned to correct the speedo, thats the only way.

 

Or you could listen to the certified Ford dude who undoubtably knows what he is talking about!

-Flea

 

haha, i'd really never even thought about it myself until i had my lightning, and i was reading up on some chip programs, and found out that the chip program was the only way to change it. The 97 and 98's do have a speedo gear though, and the 96 and downs are pretty much user programmable if you have the conversion charts.