No more manual transmissions in a Duramax - why?

I currently own a Chevy Silverado Duramax HD 4x4, with a 6 speed manual transmission. Yet I am disappointed to discover the new 08 Duramax Diesels that GM is offering, you cannot order one with a manual transmission.

I know there are fans of the Allison transmission out there, but I am a die hard manual transmission guy; all the vehicles I have ever owned had a manual transmission.

If GM does not offer another Duramax Diesel with a manual transmission, I may be owning a Dodge Ram 2500 powered by a Cummins Diesel with a 6 speed manual transmission.

Are there any thoughts as to what is going on at GM that would warrant their offering of the Allison transmission only and not having any manual transmission option available? Inquiring minds want to know.

RKL

the Cummins is a good choice, but im still not sure about the new ones, the 5.9Ls are known to be the million mile motor, this new one im not sold on yet. at least its not a mercedes, those cars, no manuals offered at all

I'm with you on this one. I specifically searched out a manual, and it was no easy task given their scarcity, so I guess therein lies the answer: people didn't buy them in sufficient numbers to warrant their production.

The reason I prefer a manual is that I feel I have way better control than driving an auto, and I only use the brakes to come to a stop. Having said that, I would welcome the opportunity to try the 6-spd Allison with the gear select (arrow up or down) on the gear-shift arm. That way I could hold it where I wanted on grades and still have the ease of auto in town.
Brett

My new service rig had an allison with the "manual" transmission option, and while I always drove the truck that way, it still didn't work like a real manual does.

I personally won't be buying a new GMC becuase of that very reason. I'm not sold on the new Cummins either, so I may wind up behind the wheel of a new Powerstroke / 6 speed instead. I have a buddy who bought a brand new 6.7L cummins, and claims that it goes like crazy, but gets absolutely terrible mileage.

My guess as to why:

Two reasons.

First, I doubt if they sold enough manuals to warrant the costs involved in developing and certifying the emissions to make it profitable.

Second, I expect emissions certification is a lot more difficult with the manual. With the automatic they can simply program out conditions that result in excessive emissions.

Remember, too, the manual D-max is derated compared to the automatic, so there must also be some durabuility issues.

Russell i think all the new diesels have terrible fuel mileage.....doesn't that come with the high HP numbers?

aside from that, i think they like selling the automatic transmission trucks because they charge more. When i was pricing out my truck, i recall i could have gotten the 6 speed manual, but i was firmly told that it was damn near guaranteed to not last as long as the allison (when driven under normal conditions).......and of course 300 hp instead of 360. But i also remember the extra cash of around $3xxx for the allison transmission option.

i could have put up with the 60 less horsepower, but it was the fact that i was trusting the guys at the dealer when they told me the allison will outlast the manual.

i guess time will tell, and i settled for the auto anyways and have no real complaints other than leaky cooling lines.....but i would still rather enjoy driving a new diesel with a 6 speed manual. I won't settle for ford, and dodge hasn't won me over just yet:confused:

The duramax has soo much torque it was wrecking the manuals.
I do not drive for a living but towing my boat thru the PA mts. and my dump trailer using the '06 allison in manual mode is fantastic. I almost never have to touch the brakes. When I fish the NJ shore I end up coming up thru the Blue Rt or "SureKill " expresss way towing my Whaler.Tough roads as most of the way is only 2 lanes. Just push the tow haul mode button and I 'am not getting cut in front and can deal w/ the short stops/fast start ups that come w/ an outdated highway.
I drive stick, learned @ 11 yrs in F350 SA wrecker ,driven many since, but I feel the Allison is overall a better choice then a stick.

Quote:

---

Originally Posted by Bravo Whiskey 21

The duramax has soo much torque it was wrecking the manuals.
I do not drive for a living but towing my boat thru the PA mts. and my dump trailer using the '06 allison in manual mode is fantastic. I almost never have to touch the brakes. When I fish the NJ shore I end up coming up thru the Blue Rt or "SureKill " expresss way towing my Whaler.Tough roads as most of the way is only 2 lanes. Just push the tow haul mode button and I 'am not getting cut in front and can deal w/ the short stops/fast start ups that come w/ an outdated highway.
I drive stick, learned @ 11 yrs in F350 SA wrecker ,driven many since, but I feel the Allison is overall a better choice then a stick.

---

I’ll have to agree. Many years ago, I gave up on ‘disposable’ automatic transmissions and drove hand-shakers for 16 years. The Allison has changed my mind, all of the benefits of control from the manual and no sore knee from driving in heavy traffic. The best part is…no more clutch jobs every 80k miles.

Incidentally, the most recent demographics show less than 15% of the population can even drive a stick much less own one. I believe the popularity of the manual in the Fjords and Goats has been due to the crappy Auto that was available in the past. Now that Fjord has the Torque-Shift and the Goat has the Aisin, things will probably change on those too.:cool:

GM insists on using a dual-mass flywheel in front of the manual tranny to keep the chatter down. Doing so creates the reliability issue. GM can't make a durable flywheel in this manner. The aftermarket provides excellent solutions to this problem, though. Want a solid flywheel? Okay. Want a double-disc clutch setup? You can have that, too, behind a Duramax.

A ZF-6 truck with 300 HP is still going to put down numbers very similar to a 360 HP Allison truck at the rear wheels. The automatic has greater parasitic loss.

Of course GM is going to sell fewer manuals if the people assume they aren't out there to be had. And people will only search for so long before they get fed up and settle for something they didn't really want. Or they shed their brand loyalty and move on to another company who will give these people what they really want. Like manual transmissions and solid front axles...

if they made the transmissions with many gears and close gear ratios so i could shift like a big rig then i wouldn't mind driving a manual pickup in the city........but since they don't make them like that, i have to admit that the auto sure makes life easier on my left leg.

from what I have seen most of the diesels are easily shifted by engine RPM no clutch needed. However I have never driven a duramax so its possible that it will not work that way.

i have to admit, i was searching for a manual truck with the 6.5L when i was looking, and i settled for the auto. sold that, looked for a manual with a 5.0L or 5.7, settled for the auto again. hard to find the 5 speed trucks. but its not so bad being able to just push a pedal to stop and go. i guess my other 5 vehicles that are 5 spd will have to do

I agree mainly 3 reasons.
1. Emissions
2. Clutch (GM just fails miserably at this from clutch pedal assembly squeak to flywheel and disc hub etc).
3. Perception and Market.

3. GM has literally STUNK at clutches since well I am not sure they ever made a nice clutch. So most GM loyalists have given up and converted to Auto's

In comparison Ford and Dodge seem better easier clutch pedal pressure and smooth quiet motion. Yeah they all tear up if you up HP and push the limits but Manuals with good clutches can be mated to high HP. Auto will still take a bit more if also built in the light trucks but again GM could do so much better....

I am hoping they will eventually try again but in 10 more yrs a manual will be a collectable.

I have to agree on the clutch pedal pressure, I have the 93 nv4500 and my brother has a dodge with the nv4500 and his clutch is so easy to press.

YEP, GM claims there is no market but Ford and Dodge easily seem to sell more manuals. Yes the numbers are dropping across all brands but GM accelerated thier numbers all on thier own and shame on them for that. When a GM salesman says its the market I feel like cussing him out.

Come on guys, it is hard enough dialing the cell phone, changing the CD, playing w/the GPS, & shoving the Big Mac in my face and have to worry about shifting. :p:p:p:eek::eek:

Hello, I am new to the forums. Not that new to diesels though. Apparently a local GMC Freightliner dealership told me that alot of Dmax's were tearing up the 6 spds. He also added the cost for redesigning a stronger unit and a less of a profit margin compared to the mark up on the Allison.

I think you hit the nail on the head. Cost is the main reason for anything they do. Nowadays I really miss my ol '93 6.5 with the nv4500. Yea it was in the shop every 4 to 6 months for pumps (lift and injection) but I would gladly tolerate that for my 17 in town and 21 to 24 on the hwy mileage. Traded it for a 454 auto (couldn't find another standard) very reliable still got it at 203k but at a price 11 in town and 14 on the hwy both empty. Yip, I have a shouldu' had a v8 moment every time I fill up.....Hmm wonder where my ol' truck is today?

I am not buying that the Duramax was tearing up many ZF's in 3/4 and 1 tons or bigger isn't it rated for up to close to 26000 lb gcvwr? Probably lots of clutch related failures though. GM doesn't make the ZF and didn't make the NV4500 either so petuie on cost of development. Funny how Southbend and a couple other manufacturers can develop a better clutch and has less money than GM too.

The 5.9 Cummins gave the NV4500 5th gear and factory clutch a trial by fire and its a bit underrated for heavy towing but after they fixed 5th and put a better clutch with it its a pretty good tranny. Yeah, you get crazy snatching around a strong engine and a big trucks something has to give.

Good point I agree more profit in selling auto's especially if you can streamline production lines and don't worry about manual options and having to credit back on sticker is really big.

I do wonder about GM's grand picture of uniform bellhousing size and interchangeability across gasser trucks 3/4 ton through 2 tons. I think this time it really limited them in clutch disc size options and if thats what has always hampered them so. Especially in a platform engine like the 6.6 that can go in bigger trucks too. But dang I kind of question if they were giving $3000 back for manual trans vs Allison why they couldn't have come off the coin for a better clutch and still given some money back. Must have been Ford and Dodge manual truck price just beat GM's too much but I don't know never compared apples to apples. Plus Ford and Dodge's automatics were thier Achilles heel another reason they sell more manuals.

I don't recall reading anywhere on the forums about the manual transmission itself being tore up by the Duramax engine. I believe it was the clutch. The reliability of the manual trans clutch was terrible relative to the Allison transmission.

My six speed has 300,000 on it and never been worked on. The dual mass flywheel is another story. I went through many till I found a single piece at South Bend Clutch.

I just replaced my transfer case (again) and Mr Good Wrench pulled the 6 speed to look for other trouble, and with 30,000 on this new single piece flywheel the surfaces looked new. the machine grooved was still there. Gotta love it!

Mike

PS I do get leg cramps in city trafic.

The 6-speed manual GM used in the 2500HD/3500 diesel pickups was identified as a "ZF S6-650". The "S6" identifies this as a 6-speed. The "650" identifies the input torque limit.

As has been mentioned here, the originally introduced flywheel was a problem. An updated flywheel was released in July 2004 that was designed to increase life, improve friction control and reduce transmission input shaft wear.

Here's a clip from an article I wrote in 2004:

Quote:

---

The ZF S6-650 six-speed manual transmission first became available in GM's 8.1L & Duramax equipped 2500HD/3500 series pickup trucks beginning in the 2001 model-year. Lower cost, improved fuel economy and a performance advantage in certain situations are among the more important reasons owners express when selecting the ZF six-speed. The S6-650 is also available on C4500 & 5500 medium duty trucks.

ZF S6-650 Key Features:

• Designed specifically for high torque pickup trucks.
• Synchronized in all gears.
• Dual-cone synchronizer in 2nd and 3rd gears.
• High helix angle gearsets provide high contact ratio and quiet operation.
• Lower shift forces w/ tight shift pattern.
• Lightweight integrated aluminum housing
  (front, center & rear).
• Center bearing support for improved durability.
• Reverse & 1st gear location improve maneuvering ease.
• Overdrive 6th gear shift lever position located forward and away for improved passenger comfort.
• Gross Combined Vehicle Weight Rating up to 26,000-lbs.
• Left & right ISO/SAE 6-bolt Power Take-Off ports.

http://www.thedieselpageforums.com/p...650-ratios.jpg

---

Jim