88 Fiero Formula LS4/F40 6 speed swap
08-13-2017, 05:49 PM
#261
Both the 3.55 and the 3.09 transmissions are now disassembled. The 3.09 case had additional reinforcements inside as well:
3.55:
3.09:
The 3.09 case also has 2 additional bolts at the base of the lower main shaft (gears 1, 2, 5 & 6):
I want to get the gears swapped with the lease amount of work, as I will be pulling the transmission again for the turbo upgrade. So right now I just want to get the gear in and see how I like them.
The only modification needed to put the 3.09 gears into the 3.55 case is to move the vss sensor closer to the ring gear. The 3.09 ring gear is a slightly smaller OD, so I need to mill the VSS boss down some.
3.55 setup:
3.09 before modding the VSS boss:
3.09 after VSS boss milled:
3.09 gear set disassembled. All I will be using are the main shafts and ring gear.
3.55 gear set disassembled:
I am now waiting on some new bearings for the two main shafts. Once they are here, I will reassemble the 3.55 transmission case halves with the 3.09 final drive gear set.
If all goes well, I might swap transmissions next weekend!
3.55:
3.09:
The 3.09 case also has 2 additional bolts at the base of the lower main shaft (gears 1, 2, 5 & 6):
I want to get the gears swapped with the lease amount of work, as I will be pulling the transmission again for the turbo upgrade. So right now I just want to get the gear in and see how I like them.
The only modification needed to put the 3.09 gears into the 3.55 case is to move the vss sensor closer to the ring gear. The 3.09 ring gear is a slightly smaller OD, so I need to mill the VSS boss down some.
3.55 setup:
3.09 before modding the VSS boss:
3.09 after VSS boss milled:
3.09 gear set disassembled. All I will be using are the main shafts and ring gear.
3.55 gear set disassembled:
I am now waiting on some new bearings for the two main shafts. Once they are here, I will reassemble the 3.55 transmission case halves with the 3.09 final drive gear set.
If all goes well, I might swap transmissions next weekend!
08-24-2017, 01:58 PM
#264
FG..
Read through the whole thread.. Awesome info for sure and a sweet project.
I was wondering which variant of the F40 you are using. They have the MU9, MT2, MZ3, MK6, and MR6.. With the MR6 having a final drive ratio of 3.762. Which is great for the hwy for sure. And the gear ratio for the MR6 is really close to my GTO 6 speed which I really like how that drives.
The other question I had was about the shifter.. I plan to do this same project in a different car (the car was cheap and the Fiero,s are hard to find here in AL). Are you using a stock Fiero or an Isuzu 5 speed shifter? and what is the shifter pattern?
Thanks,
Kev
Read through the whole thread.. Awesome info for sure and a sweet project.
I was wondering which variant of the F40 you are using. They have the MU9, MT2, MZ3, MK6, and MR6.. With the MR6 having a final drive ratio of 3.762. Which is great for the hwy for sure. And the gear ratio for the MR6 is really close to my GTO 6 speed which I really like how that drives.
The other question I had was about the shifter.. I plan to do this same project in a different car (the car was cheap and the Fiero,s are hard to find here in AL). Are you using a stock Fiero or an Isuzu 5 speed shifter? and what is the shifter pattern?
Thanks,
Kev
08-24-2017, 02:55 PM
#265
Kev, the transmission is a MYJ and here are all the final drives available for the F40 :
F84 3.091
FX4 3.348
FP9 3.545
GY6 3.762
FW4 3.895
FX2 3.909
FV2 4.176
I am using a stock Fiero 5 speed shifter (Getrag or Isuzu - they are the same).
Here is the shift pattern (same as VW):
F84 3.091
FX4 3.348
FP9 3.545
GY6 3.762
FW4 3.895
FX2 3.909
FV2 4.176
I am using a stock Fiero 5 speed shifter (Getrag or Isuzu - they are the same).
Here is the shift pattern (same as VW):
08-24-2017, 06:54 PM
#266
The ARP bolts for the differential ring gear came in, so I ran a tap down the threads to clean them, added some locktite and torqued the ring gear down (yes, I know I should install a LSD, but they are $1200 and I don't want to spend that kind of $$$ until I know I like the 3.09 gearset):
With the shafts tore down, I checked the drag torque for the preload on each shaft. The lower main one needed a shim (that I had to order), but it arrived as well. Once the preload was set, the 3.09 shafts were reassembled with the zero-mile gears and syncros from the 3.55 transmission. I also cleaned up the flanges and cases and have everything ready to go back in the case.
With the shafts tore down, I checked the drag torque for the preload on each shaft. The lower main one needed a shim (that I had to order), but it arrived as well. Once the preload was set, the 3.09 shafts were reassembled with the zero-mile gears and syncros from the 3.55 transmission. I also cleaned up the flanges and cases and have everything ready to go back in the case.
08-25-2017, 11:40 AM
#268
FG,
Thanks for the info.
Can't wait to get your review on the gear swap.
I meant to ask about the custom flywheel. are you having someone make those? I know I will need one because with out it, that LS4 and F40 will only be good for Man Cave Art and a conversation starter.. LOL
Thx,
Kev
Thanks for the info.
Can't wait to get your review on the gear swap.
I meant to ask about the custom flywheel. are you having someone make those? I know I will need one because with out it, that LS4 and F40 will only be good for Man Cave Art and a conversation starter.. LOL
Thx,
Kev
08-27-2017, 07:56 PM
#272
To replace the transmission, I didn't want to have to pull the entire engine/transmission/cradle and suspension, so I fabbed up a Fiero specific cross bar to support the engine.
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.
Here are the old and new transmission with the 3.09 final drive.
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.
Here are the old and new transmission with the 3.09 final drive.
11-05-2017, 12:34 PM
#275
Teching In
I just read over your "
initial driving experience with the 3.091 final drive" section on your personal page. I'd love to hear any more opinions you have on the swap now that you have been driving it a bit more. The one thing that drove me away from the F40 was everyone I ever drove with a V8 essentially became a 3spd stick. You used 2-4-6 for daily driving, and 2-3-4 for moderate racing. The 3.09 should effectivly space the gears out more. I know just the normal common F40 swap gives you a great top gear, on the highway. So in a percentage drop it won't go much lower. However do you feel that 6th gear is still good mild acceleration from 70mph. IE, needing to slowly move to overtake someone at 70-80mph. Back in the good ole days when I was blissfully ignorant enough to think I had the world by the ***** with a 4.9 Isuzu 5spd....... I loved the fact that 5th was near perfect in the fact that you could cruise at 80mph, or at 50mph in 5th gear going uphill, towing a trailer you could pass someone with ease never needing to downshift. (yes I do tow a trailer behind my Fiero) Obviously that was a bit of an exaggeration, but ya get what I am asking.
P.S. again, I love all the tech info you are offering up all the time. I think between you and Matt Happel I could build 10 versions of my dream Fiero and still not use all the free info you guys provide.
P.S. again, I love all the tech info you are offering up all the time. I think between you and Matt Happel I could build 10 versions of my dream Fiero and still not use all the free info you guys provide.
11-05-2017, 06:32 PM
#276
The 3.09 gear swap is probably one of my better upgrades. I really, really like the longer legs in 1st, 2nd and 6th. It no longer feels excessively over geared and feels more like a camaro with a some 3.73 or 4.10.
When I had my SBC/Getrag fiero I would often find myself doing using 1, 3 & 5th, but with the LS4/F40 I tend to row through all the gears while keeping the RPMs low. I could skip gears, but haven't really settled into doing so.
I think part of the difference is having a 142 tooth 12# flywheel vs. a 153 tooth 29 lb one, so there is much less rotating momentum to help with overly wide shifts.
I did have to adjust my driving style some with the final drive swap. Before 1st was largely a bump gear I used to get the car rolling from a dead stop. If the car was rolling at all, I would normally leave it in 2nd. Now, 2nd bogs the engine if you try to use it from a crawl (a less aggressive camshaft with more off-idle torque would likely make this a non-issue).
Driving through town in the 35 to 45 range, I would almost always be in 5th or 6th gear. Now I spend more time in 5th and occasionally get to 5th around 45, but 6th isn't used in town anymore (like it is supposed to).
On the interstate, I normally run about 78 mph, so 6th is right around 2000 rpm and the engine has plenty of torque to climb hills and increase speed as needed, but happens faster with a downshift.
I will send you a PM with some additional info.
When I had my SBC/Getrag fiero I would often find myself doing using 1, 3 & 5th, but with the LS4/F40 I tend to row through all the gears while keeping the RPMs low. I could skip gears, but haven't really settled into doing so.
I think part of the difference is having a 142 tooth 12# flywheel vs. a 153 tooth 29 lb one, so there is much less rotating momentum to help with overly wide shifts.
I did have to adjust my driving style some with the final drive swap. Before 1st was largely a bump gear I used to get the car rolling from a dead stop. If the car was rolling at all, I would normally leave it in 2nd. Now, 2nd bogs the engine if you try to use it from a crawl (a less aggressive camshaft with more off-idle torque would likely make this a non-issue).
Driving through town in the 35 to 45 range, I would almost always be in 5th or 6th gear. Now I spend more time in 5th and occasionally get to 5th around 45, but 6th isn't used in town anymore (like it is supposed to).
On the interstate, I normally run about 78 mph, so 6th is right around 2000 rpm and the engine has plenty of torque to climb hills and increase speed as needed, but happens faster with a downshift.
I will send you a PM with some additional info.
11-08-2017, 07:12 AM
#278
With the temps dropping into the 30s at night, I made room for the Fiero to barely fit in the garage bay along with the wife's Murano. So I am getting prepared for the winter projects.
The AHP AlphaTIG 200X welder was on sale for $680 through Amazon, so I ordered one. There are a lot of 1/8" steel brackets and mounts on my swap, about 4' of 1" schedule 40 black pipe for coolant tubes, and the 16ga steel smooth firewall panel. I would to replace all of this with aluminum to shed some lbs to help offset the weight of the turbo.
I have also been playing around with options to rework the accessory drive to make more room, reduce weight, and be more visually appealing. I designed and machined this manifold with integrated thermostat and coolant fill (highest point in the system). It weighs less than 6 lbs and is only 2 1/8" off the face of the block, making it shallower than the LS4 balancer by about 1/2".
When I pull the Fiero apart, I can test fit this but all my measurements and calculations indicate the closest parts with be at least 1/2" away.
The AHP AlphaTIG 200X welder was on sale for $680 through Amazon, so I ordered one. There are a lot of 1/8" steel brackets and mounts on my swap, about 4' of 1" schedule 40 black pipe for coolant tubes, and the 16ga steel smooth firewall panel. I would to replace all of this with aluminum to shed some lbs to help offset the weight of the turbo.
I have also been playing around with options to rework the accessory drive to make more room, reduce weight, and be more visually appealing. I designed and machined this manifold with integrated thermostat and coolant fill (highest point in the system). It weighs less than 6 lbs and is only 2 1/8" off the face of the block, making it shallower than the LS4 balancer by about 1/2".
When I pull the Fiero apart, I can test fit this but all my measurements and calculations indicate the closest parts with be at least 1/2" away.
11-08-2017, 10:55 AM
#279
Launching!
Oh come on! Now you're just showing off! That's AWESOME!
-KP
-KP