Upgrading To A VTD Center Diff [Forester XT]
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- Опубліковано 5 лис 2021
- The standard MPT center differential doesn't send equal power to the front and rear. Upgrading to the VTD center Diff (found on most older 5 speed automatic transmissions) Will give a better distribution of power to all four wheels.
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The VTD center diffs are found in the JDM SVX 4eat, usdm 02-07 WRX 4eat, 03-04 Legacy GT 4eat, Baja XT 4eat, 07/08 FXT Sports 4eat. Do not use the 5eat VTD from Tribeca, OBXT/LGT, 3.0R/3.6R models. The 5eat VTD will not fit the 4eat.
The VTD has a 45:55 torque split. If you wire a switch on YOUR Forester, add 12v and it'll lock. Foresters 2002 and older needs to remove the constant power to the transfer clutch solenoid. If you want the TCU to control it like OEM, you need to find the 07/08 Forester XT sports TCU. 04-06 FXT may need Baja XT TCU.
REMEMBER, the factory multi plate transfer clutch is not a differential. It's a transfer clutch. The VTD is a planetary gear differential as you can see the gears differentiate front to rear speed.
Enjoy the fun to be had with the VTD! It makes a HUGE difference in keeping front to rear power 50:50 and minimizes front wheel spin from the torque of the 2.5L. Great for off road and on road applications.
Wow, that's a mouth full! Thanks for adding all that info, I appreciate it.
Been watching for a few months now, love how you show the differences between the stock part and the upgrade, and mention issues with fitment. love learning what i can do with my 07 xt in the next year or two. Currently have a new 2.5 sti short block in the car now, now time for other goodies (hopefully a 6 speed transmission in good condition). cheers from Washington state!
Thanks for the complement. I'm considering a six speed as well but I'm not in a rush to do that, I want to find the exact parts without compromising so it will take time.
awesome! can not wait to see where your project takes you, love tuning in when i can!!
That’s a pretty cool upgrade bud, seems relatively painless to do as well. Do you have the part numbers of all those clutches/gaskets and the diff itself? I have seen/heard of companies that sell a way to lock up the stock AT FXT diff to a 50/50 style setup for off-roading purposes through like switches/power… but not sure if that’s a good long term or daily driving. The stock 5mt FXT is a 50/50 split similar to this it seems….
I don't have the part numbers but I think there is a thread about it with part numbers on nasioc.
It's not I'm a group two of them have that it's gonna chirp like a bird on concrete if you have it locked it's more of like a 50/50 for the situation your in off-road this is why I'm looking into doing this for mine cause that 50/50 would kill itself with 9inch wides on pavement
Did you run the original TCM? I just did the swap and it ran fine for about 10 miles then the trans started to slip. How much additional fluid did you add?
I'm running the stock tcu and I only added enough to bring the level back to full, about 1 quart.
Which model of car did you find it on? Looking forward to seeing it all back together and running
I got this from a friend, said it came from a 2005 Legacy GT. I recently found one on a SVX.
Is the pre-facelift SG 4EAT MPT transmission the same as the facelift SG one? Can this mod be done on the pre-facelift model?
I really like how you show and explain everything. Congrats, great video!
Yes, they are the same transmission for the xt models. I'm not sure about the na transmission though.
@@DIYEVERYTHING thank you very much!
After swap and Fwd fuse in, transmission can still making lock up to F/50R/50 when needed ? or running without locking, like default F45/R55? ( Front open, rear Vlsd).
Default is actually 90 front 10 rear. The only subaru transmission that is capable of 50/50 is the sti with dccd. The vtd center diff locks it at 40 front and 60 rear. The fuse is because the pressure now causes the front axles to lock up if it's removed.
@@DIYEVERYTHING Thanks, I was thinking the VTD could be locked 50/50 in slippery or off-road conditions. After converting MPT to VTD, I wonder if I will lose the locking advantages of MPT on slippery and off-road conditions? I guess the front fuse will not read the information from the rear speed sensor.
i know that this video is old. im desperately searching the oem part number of the cluch discs that you are using here.
There's a lot of great info on this on the forums.nasioc.com site.
Do you know the order of those big ring plates and how many are they?
I may have been overtly cautious, making sure they faced the same way going in as when they came out. They alternate between friction plate and steel plate with friction on the outside of each end. I don't remember how many there were in total.
Is this upgrade fully mechanical? No electrical or ecu upgrades needed?
Yes, with the exception of the fuse that would disable the awd system. What it actually does is prevent the front axles from locking together and causing torque steer.
I followed your video step by step because I upgraded my 06 XT 4eat. Part came of a 03 wrx but when I finished installing it, I did not put the 30amp fuse right away and drove it for like 5 minutes when the AWD light started to flash then stopped put the fuse and AWD light is on solid. Is it normal?
Yes, it's completely normal. To the best of my knowledge, without the fuse installed, the vtd center diff causes the front diff to lock and you will notice binding when you try to make a sharp turn. With the fuse installed, it unlocks the front diff to prevent the binding. I removed the gauge cluster and put a piece of tape over the light from the back side of the awd so you don't see the light or the tape.
Some people will connect a switch instead of a fuse so they can use it like a locking diff in life traction situations.
@@DIYEVERYTHING Thank you so much!
Question if anyone one knows...are VTDs more likely to fail over the Multi Plate Clutch Pack since there are more moving parts?
The planetary gears in the VTD are stronger than the clutch plates in the MPT.
@@DIYEVERYTHING Thanks. I've been looking to pickup a new Subaru Outback. Weighing the Turbo which comes with the VTD over the 2.5 which doesn't. I like the idea of a 45/55 split over a 60/40 split, and the extra power would be nice, just worried about reliability even if I'm great on maintenance.
The VTD diff itself is strong. There are less clutches than the standard MPT because you have the gears driving the output shafts. The weak part is the rear cover. When torque is applied, the rear driven gear pushes away from the VTD diff. Force is applied directly to the cover. The cover isn't very thick and doesn't have any ribs to make it stronger. Typically if you have a tranny that has hard shifts, it may break over time. It may break if you have excessive power/ torque from launching hard with higher stall torque converters.
What is the part number of plate set?
Subaruparts.com
Did you wire up a locking switch.
Not yet...
... or did I?
@@masakapubggaming6406 When swapping in the VTD center diff, the fluid pressure locks the front diff creating a hard torque steer when turning left or right. Installing the FWD fuse as I did prevents the front diff/axles from locking. Now, if you use an on/off switch instead of the fuse, you can lock the axles/differential manually for slick or icy roads but only useful when going straight and not turning.