[CrAzY dRiVeR]

Originally Posted by ezee

They have discontinued AMT because there were problems, which they were not able to solve.

Aren't we only assuming that the change in engine would make the AMT better?

AMT is still very much there and would not have benefited much unless they did software updates or any gearbox change. Either ways, if they have fixed it in new models, I don't think they would delay in providing the same fix to existing owners here since their reputation is at stake.

[humyum]

Firstly, I believe the shift quality of AMT depends mainly on synchroniser time delay(Don't remember the exact word for it, had learnt it in university some years back). I'll explain the concept.

Once a downshift is taking place, the synchroniser has to match the speeds for the shift to be seamless, this takes less than a second, that is why the downshifts are comparatively harder and slower as compared to upshifts which are butter smooth.

When I drove AMT cars, I was perplexed at the speed at which down-shifts took place, It would be okay in a car like a Celerio or an Alto which have lighter gearboxes and faster synchroniser times because of the lesser torque generating by the engines but in diesel engines that is not the case, with their stupendous torque and with AMT there is no cushioning that you get that you get in case of a torque converter which has fluid transmitting power (until the lock-up happens at higher gears though)

I believe the quick downshifts which would be happening in the AMT's of the TUV's does not match the synchroniser timing delay and hence the vibrations and jerks etc etc while shifting. In lieu to find the fastest possible shift to make AMT more usable for everyday use, I believe the synchroniser ring could end up as the victim and need frequent replacements, not to mention the jerky shift quality if the synchroniser ring time delay does not match the actual shift taking place, as its a computer doing all that and not a human who can understand who will wait for the shift to be seamless while down shifting through touch and feel.

Also a badly calibrated AMT could play a role too, but this is just my hypothesis and happy to be corrected.

PS: Sorry if this is not framed right English wise, I was thinking the cause and typing without worrying about the language to try and explain exactly what I meant.

In my Swift Diesel, 3rd to 2nd is the gear which takes the highest synchroniser shift delay, if it had an AMT unit and it went at this with the speed of light without the speeds being matched by the synchroniser, I would be looking at frequent overhauls. Also, do AMT's take into account the gearbox oil being cold during mornings and hence the synchroniser functioning even more slowly due to the gearbox not reaching its operating temperature and hence not being at its lubricating best? I think NOT.

Originally Posted by CrAzY dRiVeR

Aren't we only assuming that the change in engine would make the AMT better?

AMT is still very much there and would not have benefited much unless they did software updates or any gearbox change. Either ways, if they have fixed it in new models, I don't think they would delay in providing the same fix to existing owners here since their reputation is at stake.

Completely agree.

[ezee]

Maruti Suzuki Recalls 20,427 Units of S-Cross For Faulty Brake Part

This is how trusted companies work. Unlike Mahindra they publicly announce their recalls and accept as a fault or problem with FOC support to out of warranty vehicles too.

Till date Mahindra TUV 300 has gone for at-least 3-4 such recalls but none of them were officially announced. First was faulty Modulator, Second ECU bug in AMT, Third faulty Fuel Delivery Module (FDM) and Fourth was another ECU bug producing truck like sounds with seems many more to come in future too.

Mahindra says "WITH YOU HAMESHA" but it seems its not acting genuinely in accepting manufacturing defects, almost all recalls were done silently and on call basis (means do it when customer complains only or at the time of service). They do not mention these parts change in their invoices too, not leaving any clue about what's being done to avoid legal angle.

The biggest and one of its kind of cheating done recently, was discontinuing the faulty TUV 300 AMT mHawk80 engine and replacing it with the new tweaked mHawk100 engine with refined AMT settings. Now after enormous pressure from AMT customers Mahindra has started making changes in its website too with false promises.

See how AMT customers are regretting their decision of buying TUV 300 AMT

• First they removed a line from disclaimer - T6 AMT & T8 AMT (mHawk80) available till stock lasts

• Added a line on specifications page - mHawk80 made to order. What does that mean, who will buy a lesser powered engine just to save 8K only?

• When existing customers asked about possible upgrade then they started sending them a standard mail reply stating legal limitations in doing that.

But now these false promises and malpractices are translating in their number of sales, which is declining day by day. Common guys you have big think tanks and still screwing your business by duping customers.

[sansvk]

This is just a case where a retuned engine has been provided to improve their product and I don't see any fault in it. You pay for the product on that day, the next day the product or its price could change. Mahindra is just one example. When I booked the Titanium Ecosport, it was to be with keyless entry, start stop button, cooled glove box etc. At the time of delivery all of these features were removed and the price jacked up by 15k or so. Yes you would be disappointed and the customer is always at the receiving end. But did it stop the sales of the Ecosport or my trust in Ford? No.

[shashanka]

Originally Posted by humyum

...... the synchroniser has to match the speeds for the shift to be seamless, this takes less than a second, that is why the downshifts are comparatively harder and slower as compared to upshifts which are butter smooth. When I drove AMT cars, I was perplexed at the speed at which down-shifts took place, It would be okay in a car like a Celerio or an Alto which have lighter gearboxes and faster synchroniser times because of the lesser torque generating by the engines but in diesel engines that is not the case, with their stupendous torque and with AMT there is no cushioning that you get that you get in case of a torque converter which has fluid transmitting power (until the lock-up happens at higher gears though)

I believe the quick downshifts which would be happening in the AMT's of the TUV's does not match the synchroniser timing delay and hence the vibrations and jerks etc etc while shifting. In lieu to find the fastest possible shift to make AMT more usable for everyday use, I believe the synchroniser ring could end up as the victim and need frequent replacements, not to mention the jerky shift quality if the synchroniser ring time delay does not match the actual shift taking place, as its a computer doing all that and not a human who can understand who will wait for the shift to be seamless while down shifting through touch and feel.

Also a badly calibrated AMT could play a role too, but this is just my hypothesis and happy to be corrected.

PS: Sorry if this is not framed right English wise, I was thinking the cause and typing without worrying about the language to try and explain exactly what I meant.

In my Swift Diesel, 3rd to 2nd is the gear which takes the highest synchroniser shift delay, if it had an AMT unit and it went at this with the speed of light without the speeds being matched by the synchroniser, I would be looking at frequent overhauls. Also, do AMT's take into account the gearbox oil being cold during mornings and hence the synchroniser functioning even more slowly due to the gearbox not reaching its operating temperature and hence not being at its lubricating best? I think NOT.
Completely agree.

Hi humyum,
I must be a little slow on the uptake, so please bear with me while I try to follow....
When you say the synchronizer (I assume this is for the synchromesh g/box in current use everywhere) has to match the speeds - match which two speeds ? In the AMT, once you lift your foot from the A-pedal, the clutch disengages instantly (that is correct?) & the wheels are then - momentarily - driving the g/box which is disconnected from the engine. On down shifts, one would be expected to tap the brake pedal to reduce wheel speed (and also the g/box speed in this instance, am I right?), thus giving time to the engine (on fuel cut-off over-run) to slow down, before engaging the next lower gear. Have I followed you correctly thus far? For the driver to reduce wheel speed by tapping the brake pedal & the engine inertia reducing engine speed on fuel cut-off - are you saying that the algorithm for matching these two variables is not adequately worked into the AMT processor? A human being works the situation by slipping the clutch (in itself a bad practice!) to avoid the jerks. So would it be safe to assume that "slipping the clutch" is an operation which has not been adequately factored into the AMT?
Looking forward to enlightenment!

[humyum]

Originally Posted by shashanka

Hi humyum,
I must be a little slow on the uptake, so please bear with me while I try to follow....
When you say the synchronizer (I assume this is for the synchromesh g/box in current use everywhere) has to match the speeds - match which two speeds ? In the AMT, once you lift your foot from the A-pedal, the clutch disengages instantly (that is correct?) & the wheels are then - momentarily - driving the g/box which is disconnected from the engine. On down shifts, one would be expected to tap the brake pedal to reduce wheel speed (and also the g/box speed in this instance, am I right?), thus giving time to the engine (on fuel cut-off over-run) to slow down, before engaging the next lower gear. Have I followed you correctly thus far? For the driver to reduce wheel speed by tapping the brake pedal & the engine inertia reducing engine speed on fuel cut-off - are you saying that the algorithm for matching these two variables is not adequately worked into the AMT processor? A human being works the situation by slipping the clutch (in itself a bad practice!) to avoid the jerks. So would it be safe to assume that "slipping the clutch" is an operation which has not been adequately factored into the AMT?
Looking forward to enlightenment!

Hey Shashanka, No, by synchroniser I meant the synchronising ring in the gearbox which has a time delay between you trying to engage and it matching the speeds between the gear rpm and the shaft rpm for a gearshift to seamlessly take place.

If the synchroniser ring has not managed to match the speed, you grind the gear. Have you felt this, mostly in 2nd gear when you shift too fast to 2nd an you hear a krrrrrrk sound? That's you trying to muscle your way through the shift before the synchronisation process has taken place.

If you shift slowly, keeping steady pressure on the shifter in the car, you would have been given enough time to change the gear RPM to match that of the shaft. When it matches, no grinding of the gears. This is the synchroniser delay I was talking about in my earlier post.

Do AMT's work that way ? I don't think so? Does the computer an AMT car change any differently in hot and cold condition depending on gearbox oil temperature ? I don't think so, would you just ram you gears while downshifting without having a feel from the gearlever that it is agreeable to shift or not? Will an AMT do that? I don't think so.

I believe the synchroniser delay times are shorter for petrol cars and a little longer for diesel cars since diesels would have high torque rated synchroniser rings. What I think the TUV users are facing is a mismatch between the synchroniser ring delay time in matching speeds and the AMT just shoving gears as been programmed at whatever speed it is programmed, its a computer, it won't care if the synchroniser ring is agreeable for a shift or not, I ll shift gears as asked.

I hope, I make sense. Its a difficult thing to explain.

[humyum]

Sorry Mods for back to back posts, but please merge my posts if possible.

Just to make my hypothesis more concrete This is from the TUV 300, AMT Problems and Mahindra's inability to solve them thread by ezee

One of the points he made somehow strengthens my hypothesis further, let me copy paste what he has written from there

"But this is not the end, now facing jerks and unwanted pulling + pushing + jerks while downshifting (especially coming down from 3rd to 2nd to 1st) at low speeds. So again, taken TUV to the service center (GSP Gurgaon). This time Delhi NCR head Mr Ravi and an engineer were there to simulate problems. Taken test drives and they have agreed that there are jerks while downshifting and very inconsistent behaviour of occasional acceleration and deceleration at low speeds - also RPM shoots upto 2500 while downshifting & creating a "whoooosh" sound. But to my utter surprise, the problems I reported were quoted as normal behaviour of the AMT"

One more from the same thread

"The first problem which i felt was the crank sound in the first gear. While accelerating the vehicle to a speed of 70 to 80 the auto shift upgrades to the top gear having no problem. But when reducing the speed from 80 to parking condition the gear starts to reduce 5 4 3 2 and 1. At the end from 2 to 1 i was able to here a clear noise in downshift. This problem was reported to the service person and i was advised that this crank noise will be cleared automatically before 1 st service (3000 KM ). My vehicle has crossed the first 3000 KM mark but the sound is audible more than the initial"