i own a 1988 ford f150 4x4 and the rear gears went bad on me i was wondering what the ratio was and how salty it would be to replace .someone told me that they had installed 4.11 in it but the guy doesnt know anymore than i do thats why i rely on the expertise of this forum .any help would be appreciative........mark

 

Replacing gears in a 9" Ford third member is about as easy as it gets. Just get a good "Motor" Auto repair manual and follow the torq specs and backlash settings (you'll need to borrow a dial indicator). You can pull the center section after removing the axles and set it up in a vise instead of laying under the truck. To figure the gear ratio (assuming you have no I.D. tags)...when you get it opened up just count the teeth and divide the number of pinion teeth into the number of ring gear teeth. You can buy after-market gears mail order for around $160. If you run into problems let me know.

 

Mark/Deen,
I dont beleive you are going to find a Ford 9" axle bringing up the rear on an 88 F150. More than likely it will be a Ford 8.8" axle(83 and newer they were the predominant axle). Mark, you can tell which axle by looking at the bolt pattern,on the 9" you will see no differential cover bolts as looking at it from the back of the truck,because the entire 3rd member bolts up from the U-Joint side(front)of the axle. If it is a Ford 8.8" you will be able to count the 10 diff cover bolts from the rear of the truck. Mark you said the rear gears went bad on you? What excactly do you mean? If your rear is completely locked up you may have much worse probs than changing just the ring and pinion gears.If its making a little more noise than usual you may just need a rebuild kit. The info on swaping the R&P as Deen suggested is still the same for a 9" or 8.8",(except you will be under the truck doing it all on the 8.8").You will need to purchase a master rebuild kit along with the new R&P($60 or - $). Buy quality gears,you dont want to have to re-do it more than you have to.This is a good time to also look into installing a limited slip or some sort of traction device. With winter coming on youll appreciate the extra effort when driving slippery surfaces like mud and snow.
Jeff