Hey guys,

I am planning to do a 4.44 or 4.77 final gear swap to hit the track. As its a street/track car, i want to replace the jdm 5th gear with the US version as from what i know the US 5th is much longer than the jdm. so it will be fast on the track and sort of comfortable on the highway. It is not a high speed track. ( i barely use 4th gear anyway)

Does anyone have the gear ratio of both (to do a comparison in output speeds vs rpm anyway)

has anyone does this swap before? Anything specific to avoid or any additional parts needed other than the synchro and gear?

thanks

 

its been done, you need the two gears, main and counter shaft gears, there are two bearings you should replace, as they get pressed off and don't always like it, the lock nuts, and the 5th gear synchro, plus maybe the hub sleeve if its worn.

the US 5th is .719, there is also a .760, and a .825, so you have a few choices

 

all three options were available for the US fd transmissions?


the plan is to rebuild. the whole thing while im at it .. i have 5th gear grinding anyway from the synchro.

Are there any parts list available somewhere? or something to check out?

 

the US FD had the .719, the S4 T2 is .760 and the pickup truck is .825, Mazda uses the R type transmission in a bunch of different cars, and people have been swapping 5th since the 90's.

parts list is the same as the 5th gear synchro, but add the two gears