Dana PTU and RDM (PTU) Twin-Clutch rear drive unit -- a primer

[fossil]

The Twin-Clutch rear drive unit that can shuffle 100% of torque to either wheel and simulate a locking differential

More than traction control, new AWD systems are getting very good at optimizing traction. Take for example the Ford Maverick / Bronco Sport optional AWD system. Supplied by DANA, it’s an on-demand AWD system. This system uses a cooled Power Transfer Unit or PTU that attaches to transaxle and sends power to the Rear Drive Unit, or RDU.

The RDU has (2) clutches, one on each axle shaft that takes the torque from the prop shaft and distributes it to the wheel that needs it. These (2) clutches handle front-to-rear as well as side-to-side speed and torque biases, effectively eliminating (2) differentials, the center, and rear. When AWD is commanded, the (2) rear RDM clutches engage at the same time, allowing torque to go to the rear axle. When turning sharply, the computer partially disengages the clutch on the inside wheel of the RDM allowing it to slip to deal with the speed difference a differential would normally handle. When you “lock” the “rear diff” you are commanding more pressure more often to those clutches. The buttons are programming tricks to tell the computer you prefer traction over smooth on-road driving but “lock” nothing, not really.

Even when “locked” the systems will know to allow the required slip for turning for example. Despite this, the system is very effective, allowing for at least half and probably more up to 70% or so of the engine torque to go to the rear axle and “almost all” that torque to go to a single rear wheel. The front differential is your run-of-the-mill open type and is managed through braking individual wheels to simulate traction on a slipping wheel and allow more torque to go to a gripping one. read more

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[Maverickman74]

Nice in depth article. 2 things in particular impress me. The fact that it uses double the clutches designed for use in the Ford Edge a +10% heavier vehicle and is designed to not need extra cooling. That gives us capacity I think for decent offroading in the Tremor and makes me think the payload and towing reductions of the Tremor are not related to its clutches, more likely radiator air flow and softness of suspension.

Secondly its mounting is identical to the standard single clutch unit. That mean computer savvy maverick tuners with AWD XLs can add that their rides for custom high performance.

Can you imagine taking this truck and dropping it in 1995 LA racing scene. It would have changed modern history!

 

[fossil]

Nice in depth article. 2 things in particular impress me. The fact that it uses double the clutches designed for use in the Ford Edge

Wasn't aware of the Edge TC RDU application but first heard of it's use in the Focus RS and the Range Rover Evoque
It's a solid, proven unit. I like how the Badlands sand mode transfers all rear axle power to the outside wheel in turns, almost a trail turn assist. Hope the Mav programing does the same.

 

[Jmav2152]

TLDR;
That shit works great!

 

[colinl]

Great post. The system is very suitable for what the Maverick can do without a low-range transfer case. Without low 4x4, you cannot expect to crawl steep rocks because there just isn't enough gearing to get the torque necessary. However, in vehicles that do have that, such as the fullsize Bronco, you need an actual locking pin to literally bind the axles together so that you can definitely apply torque to a wheel that has traction. Otherwise what happens is that the torque multiplied can (and will) exceed what the clutch can handle. Maybe not immediately, but the clutch will heat up and start slipping, and it'll wear. A locking pin has none of that to worry about. But as soon as you try to turn, especially on pavement, a locker fights you and will bind.

However, the Bronco (fullsize) optional front and rear locking differentials do not have these clutches. When they're unlocked, they're actually vastly inferior performance to what we have in the Maverick Tremor because they're just an open differential. The only way to manage torque and slippage with an open differential is by applying the brakes - traction control.

 

[Maverickman74]

Great post. The system is very suitable for what the Maverick can do without a low-range transfer case. Without low 4x4, you cannot expect to crawl steep rocks because there just isn't enough gearing to get the torque necessary. However, in vehicles that do have that, such as the fullsize Bronco, you need an actual locking pin to literally bind the axles together so that you can definitely apply torque to a wheel that has traction. Otherwise what happens is that the torque multiplied can (and will) exceed what the clutch can handle. Maybe not immediately, but the clutch will heat up and start slipping, and it'll wear. A locking pin has none of that to worry about. But as soon as you try to turn, especially on pavement, a locker fights you and will bind.

However, the Bronco (fullsize) optional front and rear locking differentials do not have these clutches. When they're unlocked, they're actually vastly inferior performance to what we have in the Maverick Tremor because they're just an open differential. The only way to manage torque and slippage with an open differential is by applying the brakes - traction control.

Dont forget the one good thing about the zillion spd automatic is that 1st gear is pretty dang low, and with 30" tires. Its got a similar crawl ratio to what jeeps and trucks had back in the day. Granted their torque came on earlier thant the 2.0 but it still makes nearly as much at low rpms as any of those old inline 6s or the smaller v8s did.

 

[fossil]

Great post. The system is very suitable for what the Maverick can do without a low-range transfer case. Without low 4x4, you cannot expect to crawl steep rocks because there just isn't enough gearing to get the torque necessary. However, in vehicles that do have that, such as the fullsize Bronco, you need an actual locking pin to literally bind the axles together so that you can definitely apply torque to a wheel that has traction. Otherwise what happens is that the torque multiplied can (and will) exceed what the clutch can handle. Maybe not immediately, but the clutch will heat up and start slipping, and it'll wear. A locking pin has none of that to worry about. But as soon as you try to turn, especially on pavement, a locker fights you and will bind.

Good points
I am an active member on the broncosportforum (same user I.D.) and have been nearing 2 years. Read all the Badlands press reviews and watched the reviews and comparison videos. There was one constant, a doubt that the BSBL could get the job done without low range. What they weren't prepared for was just how torqey the 2.0 is, how good the Ford AWD system is and were amazed at just how good and fun it is. Can it crawl boulders with a Wrangler of Bronco, hell no imo, nor is it reasonably expected to. Though there a few videos that would argue with me on that point. When compared to it's peers it just wins in comparison.
I bought one for a DD, a BSBL, test drove it once. Problem was my daughter in-law went along for the drive and to ferry my Raptor home and just fell in love with the little black beast. Long story short she ended up with the title lol. What some people will do for family.
I don't agree however that the clutches in the rear are frail by any means. What I see in the bottom photo is a common type wet clutch very similar to a posi unit or a motorcycle clutch set up. These examples have been proven reliable over many years with a much higher duty cycle than the twin clutch will see. To top that off Ford plays party pooper when things warm and kills your fun for a few minutes of cooling. Honestly I haven't heard of any rear clutch failures despite what some of those turkeys do to abuse them. The PTU on the other hand may be an item worth watching and might end up being a wear item if used hard though I have no basis on that.

 

[mjkladis]

SO PUMPED TO GET THIS TRUCK SOMETIME IN 2023!! I hope to get set up and ready for Rendevous in the Ozarks. Tons of soft-roaders and Jeeps. This thing will fit right in!

 

[AUDIOZONE]

I am not in the off road clubs, so I am glad to see the tech talk here. I was wondering how much maintance is expected. Beyond oil, tires, brakes, is what i mean. Comparing a tremor to a stock xlt, fx4. Are there limited wear parts on tremor?

I have a friend who had a raptor. He told me about the dual chamber?, shocks that have to be rebuilt at 20,000? Miles. That's where my curiosity comes from.

Off road for me is mostly dry gravel roads. They can get pretty hilly, rough, sloppy, or icy. Sometimrs onto public , minimum maintenance, farm access roads. Mud holes when wet and big potholes when dry. Some stream crossings, but not much near me.

 

[Rivers90]

I am not in the off road clubs, so I am glad to see the tech talk here. I was wondering how much maintance is expected. Beyond oil, tires, brakes, is what i mean. Comparing a tremor to a stock xlt, fx4. Are there limited wear parts on tremor?

I have a friend who had a raptor. He told me about the dual chamber?, shocks that have to be rebuilt at 20,000? Miles. That's where my curiosity comes from.

Off road for me is mostly dry gravel roads. They can get pretty hilly, rough, sloppy, or icy. Sometimrs onto public , minimum maintenance, farm access roads. Mud holes when wet and big potholes when dry. Some stream crossings, but not much near me.

AWD Mavericks (AWD, FX4, and Tremor)have a PTU and rear differential, The oil in them should be changed ever 30k miles. FWD ones don't have these. I think that is the only maintenance AWD has over a FWD.

 

[fossil]

while twiddling our thumbs how about an old movie?
Bronco Sport FE (aka Badlands) good stuff starts at 3:30

 

[BackFromTheDead]

Thanks, I'm dying for some Tremor content, but Ford is observing radio silence.

 

[Kautomotive]

 

[AUDIOZONE]

AWD Mavericks (AWD, FX4, and Tremor)have a PTU and rear differential, The oil in them should be changed ever 30k miles. FWD ones don't have these. I think that is the only maintenance AWD has over a FWD.

I know this is tremor forum, but I have an xlt, fx4. I am waiting on a tremor so I will need the info later on it also.

Hello everybody. I am pulling up this old post because I am at 30,000 miles. I am talking to a dealer about this oil change and I am afraid I am saying the wrong words. two times, two dealers, dont know what I am talking about. They say the trans.ission at 100,000 miles oil change. The first dealer said it and I said let me go get my owners manual. I don't know what I am talking about and I need to find out about this. I need a price, and they quoted me for the transmission.
As I sat in the waiting room then they came to me and gave me a different price.

WHAT is the exact term I need to use, and is this a good idea oil change?, or a required oil change?

 

[Darnon]

WHAT is the exact term I need to use, and is this a good idea oil change?, or a required oil change?

You might try saying 'transfer case' even though that isn't really what it is.

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