mellonc

Question on the accessory belt on the Sport Hybrid.
1. is there an accessory belt that drives the A/C, water pump and such? If there is one, does it drive both or just the water pump?
2. Does the 3.0 have a timing chain or a timing belt?
3. Besides the Dual Clutch Transmission (or Transaxle) and the Twin Motor Unit in the back, is there any other power transfer/differential part in the Sport Hybrid?
4. I'm assuming there is no center drive shaft......
5. is the power steering electric or hydraulic?

mvl

I never looked on mine, but another forum use said they checked and most of their accessories are electric and it has no belt. I think they said power steering and waterpump are electric.

I know for certain that AC is electric, as it works even when the car is in engine-off (EV) mode.

A youtube reviewer said no driveshaft as they put the batteries in the way under the 2nd row. But again I never lifted mine up. The rear wheels are electric only so I can't conceive of why there would be a driveshaft.

MBP 03

There is no accessory drive belt on the Sport Hybrid and the water pump is driven by the timing belt.

There is no driveshaft and the rear wheels are powered only by the TMU.

The power steering is electric.

mrgold35

I think the area where the driveshaft would be on a 3.5L sh-awd is where the DC inverter sits for the hybrid. The hybrid battery pack is in the same area as the 19.4 gal fuel tank and you can add a hitch and full size spare to the hybrid. The service intervals match up to the 3.5L sh-awd MDX for fluids, filters, and rotations. The hybrid does use the same DW-1 fluid for the 7DCT and TMU. The 3.0L engine only takes 4.5 qts of oil compared to the 3.5L that takes 5.7 qts. The hybrid does have slightly larger front brake disks. No Auto Stop/Start system for the hybrid and no controls to turn on EV mode only. You can disable EV mode in Sport+ IDS mode. All MDX hybrids come with electronic dampers with comfort and sport settings and a 4th IDS Sport+ mode. There is a secondary cooling system for the DC inverter that uses the exact same coolant as the engine. I think the coolant for the DC inverter is the only service item at 105,000 miles for the EV components?

mellonc

Thanks for the comments. And, just for reference, there is no alternator to worry about.... I think.

MCRacer

I think you are correct. There is a DC-DC converter that charges the 12V battery from the high voltage battery pack and supplies the DC necessary to run 12V accy just like an alternator would. BTW I have a scangauge and when the engine is off the HV battery is still charging the 12V battery, even with AC on, headlights on, etc. the battery voltage is often at 14V

MCRacer

on (3) the power/transfer/differential is basically all electronically controlled. As you turn the system applies braking force to on rear wheel via that wheels electric motor and traction (forward) rotation via that wheels electric motor to the other to make the car more neutral handling. And applies power independently to each rear wheel in forward motion with traction control if needed. And the front electric motor is coupled and part of the transmission so again it applies traction force as needed. And for regen braking the 3 motors are run as generators to recharge the batteries.
One thing at least the front motor does NOT work in reverse, it relies only on the gas engine. I think the same applies to the rear motor. the gas engine comes on anytime you select reverse. And in reverse you can feel the typical clutch "judder" that is eliminated via the front electric motor. Acura is one of or maybe the ONLY mfg that uses DCT with either an electric motor or torque converter to solve the big complaint of DCT transmission, clutch judder when starting from a stop. Even with all the electronics, they haven't surpassed what a good driver can do with smooth clutch engagement from a stop without the aid of either a torque converter or electric motor.

BTW the rear motors don't function above about 84mph, that's the rev limit on the rear electric motors.

mrgold35

I wonder if it is a programing thing or cutting corners thing for the MDX hybrid to turn on the 3.0L in reverse? My RLX hybrid can use electric power only from the TMU in reverse.

mvl

I haven't complained about clutch judder in reverse since hearing it's common from various forums. However, in the last week the judder has progressed from quiet shaking to thudding on my 2020 hybrid (55k miles). I also heard (but didn't feel it) once when quickly stopping from 50 to 0 on a divided highway uturn. MDX is at dealer now for CPO warranty diagnosis/repair, but to help them figure out if not reproducible, is there someplace I should tell them to look, like the equivalent of a clutch disk wearing out?

mrgold35

The +14 RLX hybrid owners suggested changing out the 7DCT DW-1 fluid every 30,000 miles or 3-4 years to keep the transmission happy.

mvl

Last 3x ATF was at 40k, so 55k seems too early.

I have a suspicion: Resuming from a stop light with ACC on the Hybrid creates a frequent thud, and once it revved the engine and threw a transmission code while I could smell a burn. My suspicion is that the ACC is improperly programmed on resume from a stop light and probably does the equivalent of popping the clutch in the process. So I would not be surprised if the equivalent of a clutch disk is worn out, since I get this thud multiple times a day.

Hopefully the dealer can figure this out, if the clutch isn't accessible they may swap the DCT as long as I can find a reliable reproduce scenario. Will try the uphill reverse.

MCRacer

1) there is a recall on some of the hybrids to reprogram the transmission due to some shifting problems.
2) change the transmission fluid at least every 30K miles, I do mine every other oil change which is every 15-20K miles.

I never notice any clutch judder in forward gears, only a very mild shudder when slowly backing especially on a slight incline.