I have a 90 Bronco with 3.55 gears (according to my Ford build sheet) right now. I came across a Ford 9" with 3.50 gears and limited slip. This is an obvious upgrade over my 8.8" with open diff.

However, since the 9" is a 3.50 ratio, and my front axle is a 3.55 ratio, are these axles compatible? I know they aren't the same ratio, but are they close enough? I sure it sould be fine in dirt or snow, but what about using 4wd in the winter and coming across a clean spot of pavement suddenly?

-Jim

 

yes they will work out fine, this is what i am running currently. just dont run 4x4 on dry pavement ever or even wet pavement still may cause a slight bind but in any other surface you will be fine

late

 

Your front axle is actually a 3.54, with your current rear a 3.55. The rule of thumb is that as long as they're within 1%, you're fine.

 

Guys, not to intrude on the thread but I am sitting here trying to recall whether the 9" and the 8.8 have the same pinion-to-driveshaft setup. I know the 8.8 has the flat flange on the pinion adn the same on the rear U-joint. Will that flange swap or does it need to change? This thread made me wodner whether or not to bring the point up.

 

lets see if i can explain this correctly. my 9" that i swapped in had a had a regular pinion yoke. and my tcase also had the same setup so using my stock ds was no problem. but a fellow FSBr with an 87 tcase same model 1356 had that flat flange type setup. so i guess thats something you need to look out for.