IRS differences
09-18-2018, 11:22 PM
#1
Thread Starter
Join Date: May 2018
Location: Kentucky
Posts: 6
IRS differences
are all the GTs IRS’ created the same? I noticed that the Torsen (spell) differential says it only works with rears that are equipped with 3:55-4:410 gears. Mine is a 3:15. If I change gears with the carrier are all other aspects the same, ie.... will the axles work?
09-19-2018, 04:30 AM
#2
Banned
Join Date: Jan 2018
Location: Pennsylvania
Posts: 2,327
If they did anything like dodge, axles can be different from V6 to V8s. Dodge had three different
RIIs for the LX platform. Their 198RII was for the 2.7 and 3.5s. Then they had the 210RII and
215RIIs for the R/T and SRT. The 210 and 215s used larger axleshafts, but the carriers still bolt right
in, and use the same flanges for the driveshaft.
RII is Rear Independent Iron (carrier).
Gearing did not determine the axleshaft size,. Mine was 2.87, and I went to a 3.64, same
axleshafts, as both were 198RIIs. This one from a 2.7 V6 model... Tons of gearing options
for these carriers, and I got my 3.64 for $50.00 on eBay...
I would assume Ford did the same thing, the 5.0 carriers would use larger diameter axleshafts.
The Ecobost and 3.7s should be the same, the V8s should be larger.
RIIs for the LX platform. Their 198RII was for the 2.7 and 3.5s. Then they had the 210RII and
215RIIs for the R/T and SRT. The 210 and 215s used larger axleshafts, but the carriers still bolt right
in, and use the same flanges for the driveshaft.
RII is Rear Independent Iron (carrier).
Gearing did not determine the axleshaft size,. Mine was 2.87, and I went to a 3.64, same
axleshafts, as both were 198RIIs. This one from a 2.7 V6 model... Tons of gearing options
for these carriers, and I got my 3.64 for $50.00 on eBay...
I would assume Ford did the same thing, the 5.0 carriers would use larger diameter axleshafts.
The Ecobost and 3.7s should be the same, the V8s should be larger.
09-19-2018, 07:30 AM
#6
Thread Starter
Join Date: May 2018
Location: Kentucky
Posts: 6
Forgive me for being a doubting Thomas but a little while ago you didn’t know, now your sure they’re all the same. My original question is about GTs. Mine is a GT with 3:15s (auto) and Summit sells 2 carriers for the IRS and both say they only work with the 3:55 and up gear ratios, so what is different and can I swap gears and carrier or can I only swap gears in my IRS.
09-19-2018, 03:22 PM
#7
Banned
Join Date: Jan 2018
Location: Pennsylvania
Posts: 2,327
As far as AXLES working, they're all the same. If you go to sites that sell axles, they
indicate for Ecoboost, V6 and GT. I was only stating with the dodge, they had different
size axles, but every carrier bolted up without any modifications.
Flanges are also different with auto and manuals.
There is no need to change the ring and pinion gear when the carrier is swapped out.
Buy a carrier that has the gearing you want. IF you need a flange because it's
from manual, then get the correct flange. The carrier IS the differential, and with IRS
swapping them takes about 2.5 hours with the right equipment and tools. Of course,
first time swap there is a learning curve, so maybe 3.5 hours...
Example:
https://www.summitracing.com/parts/f.../model/mustang
Direct fit for manual transmission vehicles, Automatic transmission vehicles must purchase separate pinion flange.
https://www.summitracing.com/parts/f.../model/mustang
https://www.summitracing.com/parts/f.../model/mustang
Does not say it only fits certain carriers, just that you need an install kit. They are 30 spline count.
THIS:
https://www.summitracing.com/parts/f.../model/mustang
Still physically fits in a 3.15 carrier, but won't work in it because it's not equipped for it.
https://www.summitracing.com/parts/f.../model/mustang
Won't work in factory 3.15 because the spline count on the pinion gear isn't the same, at 34 -vs- 30.
Fitting and working are two different things....
Swapping gears inside the carrier is the same as changing gears in a solid axle differential.
The benefit of having an IRS with a carrier, is every other Mustang IRS carrier for that platform
will bolt right in. You need the tuner to change the gear ratio in the ECU.
indicate for Ecoboost, V6 and GT. I was only stating with the dodge, they had different
size axles, but every carrier bolted up without any modifications.
Flanges are also different with auto and manuals.
There is no need to change the ring and pinion gear when the carrier is swapped out.
Buy a carrier that has the gearing you want. IF you need a flange because it's
from manual, then get the correct flange. The carrier IS the differential, and with IRS
swapping them takes about 2.5 hours with the right equipment and tools. Of course,
first time swap there is a learning curve, so maybe 3.5 hours...
Example:
https://www.summitracing.com/parts/f.../model/mustang
Direct fit for manual transmission vehicles, Automatic transmission vehicles must purchase separate pinion flange.
https://www.summitracing.com/parts/f.../model/mustang
https://www.summitracing.com/parts/f.../model/mustang
Does not say it only fits certain carriers, just that you need an install kit. They are 30 spline count.
THIS:
https://www.summitracing.com/parts/f.../model/mustang
Still physically fits in a 3.15 carrier, but won't work in it because it's not equipped for it.
https://www.summitracing.com/parts/f.../model/mustang
Won't work in factory 3.15 because the spline count on the pinion gear isn't the same, at 34 -vs- 30.
Fitting and working are two different things....
Swapping gears inside the carrier is the same as changing gears in a solid axle differential.
The benefit of having an IRS with a carrier, is every other Mustang IRS carrier for that platform
will bolt right in. You need the tuner to change the gear ratio in the ECU.
Last edited by 08'MustangDude; 09-19-2018 at 03:30 PM.
09-19-2018, 11:00 PM
#8
Thread Starter
Join Date: May 2018
Location: Kentucky
Posts: 6
Ok, I thank you for trying to help and because you are all over the place it lead me to the places I needed to get the correct info. You might have all the info but you are not presenting it in a coherent way.
“https://www.summitracing.com/parts/f.../model/mustang
Direct fit for manual transmission vehicles, Automatic transmission vehicles must purchase separate pinion flange.”
This is is a loaded differential housing. This has a differential inside it, and all the other components also. This is also the Super 8.8 which I have not found out what the difference is yet but it seems to only be associated with the rears with 3:31 and ratios. This set up would be cheaper than buying a differential/gears/install kit and having installed in my housing.
“https://www.summitracing.com/parts/f.../model/mustang
https://www.summitracing.com/parts/f.../model/mustang
Does not say it only fits certain carriers, just that you need an install kit. They are 30 spline count.”
These are ring and pinions and only fit differentials made for the 3:31 and higher gears.
“https://www.summitracing.com/parts/f.../model/mustang
Still physically fits in a 3.15 carrier, but won't work in it because it's not equipped for it.”
I have no idea what you mean by not equipped for it . That differential will mount in the housing but has to have the 3:31 and higher gear installed with it.
“https://www.summitracing.com/parts/f.../model/mustang
Won't work in factory 3.15 because the spline count on the pinion gear isn't the same, at 34 -vs- 30.”
The 30 splines on the pinion have nothing to do with the 34 splines in the differential that the axles go into. All axles use the same 34 splines which you correctly stated earlier. From what I’m figuring there is a break point in which the differential size limits the ring gear that is able to be installed, either larger or smaller. Just guessing here but I think that I can not change to 3:73s on the stock differential that is 3:15. The differential will have to be changed with the gears. Some one correct this if I’m misthinking this.
“https://www.summitracing.com/parts/f.../model/mustang
Direct fit for manual transmission vehicles, Automatic transmission vehicles must purchase separate pinion flange.”
This is is a loaded differential housing. This has a differential inside it, and all the other components also. This is also the Super 8.8 which I have not found out what the difference is yet but it seems to only be associated with the rears with 3:31 and ratios. This set up would be cheaper than buying a differential/gears/install kit and having installed in my housing.
“https://www.summitracing.com/parts/f.../model/mustang
https://www.summitracing.com/parts/f.../model/mustang
Does not say it only fits certain carriers, just that you need an install kit. They are 30 spline count.”
These are ring and pinions and only fit differentials made for the 3:31 and higher gears.
“https://www.summitracing.com/parts/f.../model/mustang
Still physically fits in a 3.15 carrier, but won't work in it because it's not equipped for it.”
I have no idea what you mean by not equipped for it . That differential will mount in the housing but has to have the 3:31 and higher gear installed with it.
“https://www.summitracing.com/parts/f.../model/mustang
Won't work in factory 3.15 because the spline count on the pinion gear isn't the same, at 34 -vs- 30.”
The 30 splines on the pinion have nothing to do with the 34 splines in the differential that the axles go into. All axles use the same 34 splines which you correctly stated earlier. From what I’m figuring there is a break point in which the differential size limits the ring gear that is able to be installed, either larger or smaller. Just guessing here but I think that I can not change to 3:73s on the stock differential that is 3:15. The differential will have to be changed with the gears. Some one correct this if I’m misthinking this.
09-20-2018, 05:07 AM
#9
Banned
Join Date: Jan 2018
Location: Pennsylvania
Posts: 2,327
https://www.summitracing.com/parts/f.../model/mustang
Won't work in factory 3.15 because the spline count on the pinion gear isn't the same, at 34 -vs- 30.
NO, right in the detail, it says the PINION GEAR is 34-spline, not axle anything.
Pinion Spline Count: 34
All the other ones say 30.
Whatever man, the information is out there....
The 3.15 carrier must then be a smaller housing?
Won't work in factory 3.15 because the spline count on the pinion gear isn't the same, at 34 -vs- 30.
NO, right in the detail, it says the PINION GEAR is 34-spline, not axle anything.
Pinion Spline Count: 34
All the other ones say 30.
Whatever man, the information is out there....
The 3.15 carrier must then be a smaller housing?
09-20-2018, 05:12 AM
#10
Banned
Join Date: Jan 2018
Location: Pennsylvania
Posts: 2,327
For the 2015-2017:
Also there is a difference with the pinion flanges between a 6R80 (aluminum case) and the MT82 (iron case).
For the 2018/19:
Depending on if you are buying new or used, the Performance Pack equipped Mustangs all have a Torsen rear
with 3.73’s (GT) or 3.55’s (EB or GT) and the cases are iron regardless if the trans is the new 10R80 or the MT82.
Again, be aware of the auto vs. manual trans rear diff pinion flanges. Another thing to be aware of for 2018/19 rear diffs,
if it matters to you - the 2018/19 PP rear diff cover is pre-drilled for the rear axle temp sensor. I’m not sure if the diff
cover on a 2018/19 w/3.15’s even has the sensor.
Also there is a difference with the pinion flanges between a 6R80 (aluminum case) and the MT82 (iron case).
For the 2018/19:
Depending on if you are buying new or used, the Performance Pack equipped Mustangs all have a Torsen rear
with 3.73’s (GT) or 3.55’s (EB or GT) and the cases are iron regardless if the trans is the new 10R80 or the MT82.
Again, be aware of the auto vs. manual trans rear diff pinion flanges. Another thing to be aware of for 2018/19 rear diffs,
if it matters to you - the 2018/19 PP rear diff cover is pre-drilled for the rear axle temp sensor. I’m not sure if the diff
cover on a 2018/19 w/3.15’s even has the sensor.
