So I plan on buying some gears here pretty soon and I just wanted to know exactly everything I need to buy to take to my mechanic. I planned on getting the 4.77 fd from Kia and buying the yellow box online for the speedometer. What other parts would I need for installation? Also would I wanna buy the reinforced differential housing? I daily drive it and hardly get on the highway so most of my driving is in the city that's why I went with 4.77 and I'm also driving an ap1. I don't plan on taking it to the track and I don't drop the clutch often. Thanks

 

Doesn't sound like your driving or power level warrants a reinforced diff. But depending on what stage/level you reinforce, it may be worth the money since you are already paying someone to be in there doing the gear swap. If nothing else just for the resale value when you get tired of shifting all the time The typical first failure point on the ap1 diff is the carrier bearing end caps, these can be easily upgraded during the gear replacement process, how much $$ I don't know off hand, several companies make options, some replace the entire cap and some just add an additional stack to the OEM one.

 

Oh i was reading that the housing was mainly cars with more power or for the people that just wanna be safe but okay cool I'll check that out. So I would need to buy the installation kit from htg also right? And I don't think I will mind shifting constantly it will definitely be worth it for me!

 

I have Ap1 + 4.77. You don't shift that much, I'm usually cruising in 3rd or 4th, cornering in 2nd or 3rd. 4.77 is great for city driving. Shifting at 4000 and cruising at 3000 rpm.

 

Will I feel a pretty big difference? And did You put them on ur stock differential or did u get one built from htg?

 

I had it already on the car when I bought it (ricks or j's, don't know for sure), but from what others told me, it's like having a 2500cc engine city-driving.
If feels like it has more torque.
Btw, top speed is about 231 km/h but the speedo went over 270 km/h. I have yet to install the speed calibrator but I have it as well.

 

Do you know if I need to buy the installation kit? Or does the set from Kia come with everything?

 

I bought a used kia differential and all that I had needed was the sleeve on the pinion. The old one was to short. When i tried to adjust the turning torque, it was out of spec. But with the new sleeve, everything was good.

 

Since you will have everything apart,might as well change all the bearings,seals,washers,and pinion nut.You may also want to change the ring bolts as well at the carrier cap bolts.You can get a small discount on the bearings by ordering them from the Mazda dealer. The seals I used were from Honda. You may have to give your mechanic a couple crush sleeves unless you decide to get a j's racing differential collar spacer.i believe s2kpuddydad sells a heavier duty crush sleeve you can use as well.