LS4 / F40 swap - fieroguru (Page 126/216)
FieroWannaBe AUG 10, 01:49 PM
The amount of reinforcement on the differential is impressive. Looks very much like the Regal F40 housing .
For all the observers here, I currently have a few F40 transmissions from various applications to build this gear package (one day). This transmission is very popular still in European cars from Opel and Alfa Romeo, and was in the Buick Regal after GM cut Pontiac. Only the G6 version had the GM Metric V6 bell-housing though.

code:

FD from 2003    FM68:   3.91
1st from a 2006  MT2:   3.77  overall 14.74
2nd from 2006    MT2:   2.04  overall 7.67  split .54
3rd from 2007    MU9    1.37  overall 5.15  split .67
4th from 2007    MU9    1.05  overall 3.95  split .77
5th from 2007    MU9    0.85  overall 3.20  split .81
6th from 2006    MT2    0.62  overall 2.78  split .73
fieroguru AUG 12, 04:10 PM
The donor...


Open case halves:



Initial breakdown:



Disassembled:


The 3 key parts to the 3.091 (68/22) final drive swap. Upper Main Shaft, Lower Main Shaft, and Differential Gear.

FieroWannaBe AUG 12, 09:38 PM
Now looks like a great time for a wavetrac or quaife. Especially wuen going turbo.
fieroguru AUG 13, 09:43 AM

quote
Originally posted by FieroWannaBe:

Now looks like a great time for a wavetrac or quaife. Especially wuen going turbo.



A LSD isn't in the budget right now, but I did spend an hour figuring what the difference is between the F35 and F40 diffs as the F35 has an OBX LSD for about $335, but it would place the ring gear in the wrong position.
fieroguru AUG 13, 01:08 PM
I started taking the G6 F40 apart and verified a few things. The ring gear for the 3.09 final drive is smaller than the 3.55 one, so I will need to move the VSS closer to the ring gear. The good thing is that there is extra material I can mill away on the case to move it in closer.

3.55 final drive:


3.09 final drive:


The case bolt patterns between the two transmissions are not the same. The 3.09 case has 2 extra bolts under the lower main shaft (bottom side of the transmission). The lower main shaft is for gears 1, 2, 5 & 6 so it sees the highest torque loads. I could probably drill the 2 missing holes and make a bolt on brace of something to pick them up on the other side.


Some slight clearancing would be needed for the clutch line bleeder assy to fit.


The differential bolt pattern on the bellhousing side is completely different. No 2 holes line up to the holes with the G6 case.


Some other pics of the two cases bolted together:



The outside of the gear side cases clearly shows additional reinforcing with the 3.09 case, but the same is also true on the inside as well:
3.55:

3.09:


The bellhousing side is also deeper on the 3.09 case than the 3.55.



I think for now, I am just going to swap the final drive gears into the G6 case. This will be the least amount of work (just need to mill down the VSS boss) and then the transmission would be plug & play with the one in my car. This would allow doing the trans swap over a weekend and be back driving the car to see how I like the setup before putting a lot more time and effort into the other upgrades.

I need to take a few more measurements before I disassemble the main shafts. I am also waiting on new bearings for the main shaft. The ones with the 3.09 main shafts were used and the bearings on the final drive end were destroyed in removal.
fieroguru AUG 13, 05:32 PM
There was sufficient additional material as the VSS boss to mill away the needed amount to put the VSS at the same clearance to the 3.09 ring gear.




I also finished disassembling the 3.55 gear set:



If I wasn't waiting for the new bearings for the main shaft, I would already have the gear swap completed... My goal is to finish up the swap this week and swap the transmissions next weekend...
FieroWannaBe AUG 14, 09:23 AM
Are there crush sleeves for the differential bearings in these transmissions?
fieroguru AUG 14, 01:34 PM

quote
Originally posted by FieroWannaBe:

Are there crush sleeves for the differential bearings in these transmissions?



No crush sleeve anywhere in the transmission.

The differential does call for shims behind the outer bearing race on the bellhousing side to set the preload.
fieroguru AUG 25, 10:13 PM
I moved most of the details of the F40 final drive swap to this thread: http://www.fiero.nl/forum/Forum1/HTML/097738.html

ARP bolts on the 3.091 ring gear:


Main shafts and ring gear swapped and everything cleaned ready for installation:



Painted and nearly ready for installation:
fieroguru AUG 26, 07:47 PM
I lost a few hours today making this engine support bar in preparation of removing the transmission. The brackets on the side have a bolt that locks into a hole in the strut tower and there is a leg on the other end that rests on the upper frame rail. The cross bar bolts to these side brackets and once tight everything is locked into place. I wrapped several areas of the side brackets with 5 wraps of electrical tape to help reduce chances of scratching the paint.