Hopefully you guys can help me out cause I am stumped. I am looking at the specs from a Manual TL and Auto TL and these are there front final drive ratio's"

AT: 4.53:1
MT: 3.84:1

Ok...So if there front final drives are different....than there rear differential ratio's must also be different. But when I look up there part numbers they both have the same rear differential part number:
41200-RWG-080 CARRIER ASSY., RR. DIFFERENTIAL

OKokok.....so you they both have the same rear ends. I got this than. They must have different transfer cases than so that makes up for the different final drive ratio. Nope. Same part number there:

29000-RK4-000

OKOKOKok...so I bet they have the same case, but the gears inside are different and that's what allows the car to use the same rear diff. NO AGAIN. they both have the same part number for there for they hypoid gears.

29200-RYF-000 GEAR SET, TRANSFER HYPOID


Oh SOB...I'm lost at this point. That would run HAVOC on the AWD system with the different final drive ratio's but the same rear diff ratio's.
Where am I going wrong here people? Where am I making a mistake?

 

I had to read this 2x... at first I thought you were confusing front and rear diffs with Auto and Manual, but then I re-read. My guess is that the different ratio is a result of the gear box, not the differentials.

 

I could be wrong, but I'd think the AWD would know if it's in an AT or MT, so even if the ratio's were different it shouldn't affect it, no?

 

TO respond to both of the above posts.....are you saying you think its ok that the final drives are different and it won't affect things?

I don't know. THis is what I think. I think the take off for the front transfer case is independent of the front final drive. So as long as the front transfer case gears and the same than the rear diff gears can be the same as well.

 

^.... yes.... i think haha.

After reading ur first and 2nd post again, I think i get what you're asking now, and I would also come to the conclusion that the diff ratios are the same in AT and MT, if their part numbers are the same, but the tranny ratios are different (obviously).

As for the final drive affecting things, also remember, this is SH AWD, key being SH. Now, somebody chime in if im mistaken, but i was under the impression that the SH (ATTS) is what controls the AWD. So even if the diff ratios were different, it could be ironed out in SH programming.

 

You could be right that it gets ironed out in the programing, but can those clutches in the rear diff really take that much slipping? The answer is maybe actually. I have found that the SH all wheel drive is set up to have a 1.7% higher drive in the rear diff to over drive the rear wheels. One crazy thing is that the Acura RL diff has another set of clutches that can engage to overdrive the rear 5.7%, but I think it will only do it in corner situations when applying power to the outside wheel, which would spin faster in a corner situation anyway so its not really over driving the whole system.

What is clear is that it does over drive the rear 1.7% when it does engage so there is the ability of those clutches to take a good amount of slip, all the time.

I say all the time, because no matter what the rear is always engaged by 10% right? From what I have read the car when cruising in a straight line is 90/10 front rear ya?

 

Here is your answer for slippage, and yes it slips all the time apart from when full torque is required.

Direct Electromagnetic Clutch Systems
Two direct electromagnetic clutch systems mounted on either side of the hypoid gear that drives the rear axle control the amount of torque sent to each rear wheel and provide a limited-slip differential function when needed. The clutches can be controlled as a pair to alter front/rear torque split or they can be controlled independently to allow 100-percent of rear axle torque to go to just one rear wheel.

An electromagnetic coil modulates the pressure controlling each clutch pack, which changes the speed of the sun gear within a planetary gear set thereby controlling the torque sent to the wheel. Electromagnetic control of the clutches permits torque delivery to each rear wheel to be proportioned in an exceptionally quick and precise manner, which reduces wheel-slip in low-traction conditions.

The clutch packs and their friction material are carefully designed to withstand the small amount of continuous slip between front and rear axles (created by the 1.7-percent speed differential) while delivering the durability expected of an Acura product. Through an oil-temperature sensor, the PCM monitors the clutch-plate coefficient of friction (which changes with temperature) in each clutch pack and then adjusts the voltage to each electromagnetic coil to compensate. As miles accumulate, the PCM uses data from a feedback loop to adjust the voltage supplied to the electromagnetic coils to compensate for any clutch wear, ensuring optimal and consistent transmission of torque.

Copied from the best technical review I've seen (apart from the 2 bible sized service manuals from Acura I have) on this car at http://www.topspeed.com/cars/acura/2...l-ar80141.html

 

^^^^^

Any mentioning of the service life for the wearable clutch packs ?

 

Good question. I will check to see if the service manual states this at all when I can find time! I'm sure the local Acura dealer might know as well.

My guess is that those who use the SH-AWD system heavily (i.e where the rear wheels are actually required for cornering and acceleration) will have longer life as there is less slip on the clutches

 

Does it mean that the SH-AWD is not designed for high performing driving which demands powering into and out of corners at speed all the times ?

 

Checked the technical manuals, no mention about life of the clutches. They show how to test for proper engagement and test, but it requires the Honda Data Link software to enable the clutches, and you then enter the torque values back into the software to get a 'pass' or 'no pass' indication.

I'm sure being Honda/Acura it will outlast the bodies of the cars as usual (ours all die of rust here in Canada in 8-12 years. My guess is 200,000 mi would be a good number??

 

As a street car I would say it's fine, as a track car different story. I think heat would be the enemy here, so I'm sure there is a way to attach a fluid cooler with a pump system if you really wanted to.