[smass]

I recently went to MHD stage 1 and my 2010 150k mile 6HP21 started slipping. Rather than fix it, I have purchased an 8HP45 from a 2016 435i. I have had the 8HP in several other cars and it is just perfect for my driving style. My 335i will never go beyond stage 1+ (we have emissions here) so I decided to go with the 8HP45. The stronger 8HP70 needs an adapter plate and is more expensive.

My build will attempt to make the 335i perform like a stock G series 340i.

Here is what I have on order so far:

F32 8HP45 transmission and torque converter
CAN TCU, PnP harness and shifter mounting adapter from CANFormance Adapter for 6HP21 transmission cooler lines to 8HP45 (11.6mm to 18.6mm)
F10 shifter - E90 DTC would be my preference but I can't find one
Steel bell housing bolts to replace aluminum ones
Exhaust gaskets
TX pan/filter and fluid
Rear main seal for N54
XHP for the 8HP


I also plan to replace my rear dif with a 3.08 ratio (8HPs are usually paired with 3.12) from the manual trans 335i E90. I think I also need the axle shafts. M3 LSD dif is also an option but that needs a custom drive shaft. I want the 3.08 to make 1st gear usable, lower highway RPM and increase +3 MPG.

Does anyone know of a good resource for info on the dif swap? Thanks!

[335i54n]

seems legit garage probably has all the measurement and would be my option. m3 lsd (3.15) axles and slg custom driveshaft

[Chris@BoostConcepts]

Originally Posted by smass

Does anyone know of a good resource for info on the dif swap? Thanks!

I did the manual diff swap on a 135i with the 6hp, it requires the manual driveshaft and axle shafts from the manual donor, all else went together like factory. Not sure of a driveshaft will be needed with the 8hp if it is longer, if so the auto drive shaft length might work??? Would have to check the trans length difference and driveshaft lengths. The diff and axles from the manual car will bolt in directly. Hose down the axles at the wheels hub with PB blaster, those things can be seriously stubborn.

Hope that helps some!

Please post your findings as im also looking at an 8hp swap and the drive shaft was one of my question marks.

Best regards,

Chris

[smass]

Originally Posted by Chris@BoostConcepts

I did the manual diff swap on a 135i with the 6hp, it requires the manual driveshaft and axle shafts from the manual donor, all else went together like factory. Not sure of a driveshaft will be needed with the 8hp if it is longer, if so the auto drive shaft length might work??? Would have to check the trans length difference and driveshaft lengths. The diff and axles from the manual car will bolt in directly. Hose down the axles at the wheels hub with PB blaster, those things can be seriously stubborn.

Hope that helps some!

Please post your findings as im also looking at an 8hp swap and the drive shaft was one of my question marks.

Best regards,

Chris

I picked up a MT dif and it is around 1" wider than my AT one. Late build AT 335i have the small dif. The MT axle shafts are about 1/2" shorter.

The auto driveshaft is 2 mm longer than the manual. Strange that BMW made such a small change. The 6HP21 and 8HP45 are supposedly the same length. I am probably going to do the dif install first to make sure the driveshaft is not an issue.

This is an AZ car so hopefully the axle comes out easily. Thanks for the reply.