08 Manual or Automatic

[TLane]

Sorry about the mess with the table. The forum software apparently removes multiple consecutive spaces, so the column layout got squished into a mess. I went back and edited it and replaced the spaces with periods. Interesting, the spaces were still there when I went to edit it. Hopefully it's a little easier to read now. The gear ratios for the auto are the 68RFE, the manual is the G56; based on the information I found online. I think these may have changed over the years so its possible I got the wrong ratios or they may not apply to older trucks.

If anyone wants the original spreadsheet, I'll be glad to send it to you. You can plug in your rpm/mile for your tires, your ratios, etc. Send me a PM with your email address if you want it.

 

[TLane]

I'll try uploading a screen shot of the spreadsheet:

 

[HBarlow]

Nice job now. Thanks.

 

[FParisi]

Thanks for the chart- just what I was looking for.

I'm looking at pulling the trigger on a new '09 2500 Crew cab long bed that comes with the 4. 10 + had wondered if that would be OK for empty freeway driving.

How high do these new truck rev? I got the 3,000rpm kit in my old truck which, with other mods make it very driveable.

I'll have to test drive but it sounds like it should be fine.

Thanks

Frank

 

[DGamelin]

I shift my 04 at 3000 when pulling hills loaded. I wish I had 410s so munch that I am thinking about changing them. These trucks dont mind the rev's at all.



_________________________

93 250 2wd xc 354 auto 267k

04. 5 3500 4wd cc dully 373 6speed 90k

 

[Wygate]

I can tell you for a fact that the 610lb is a derated 6. 7. During the testing phase of the 6 speed manual it was found that the clutch would only hold that magic 610lb not the 650 the auto has. This is strait from the mouth of one of the engineers that was on the 6 speed manual job, a close friend of mine. If they wanted to go up to the 650 they would have had to use a much more expensive clutch, in the end it is always money.



I was on the same fence you are on and that info pushed me to the auto.

Hope that helps.

 

[HBarlow]

Thanks for the chart- just what I was looking for.
I'm looking at pulling the trigger on a new '09 2500 Crew cab long bed that comes with the 4. 10 + had wondered if that would be OK for empty freeway driving.
How high do these new truck rev? I got the 3,000rpm kit in my old truck which, with other mods make it very driveable.
I'll have to test drive but it sounds like it should be fine.
Thanks
Frank

4. 10 differential gears with the six speed automatic which offers two overdrives provides a near perfect set up for launching heavy loads up a steep grade, for towing heavy at any speed, and for high speed interstate highway cruising without a load.

The new six speed automatics are well designed with good gear spacing, automatic activation of the exhaust braking feature for engine braking when towing, and are far more durable than the six speed manual with dual mass flywheel.

 

[Scrappy]

I have had 3 Cummins powered trucks, an '01, an 03, and now an 07.

the first 2 were HO/ 6spds. and this one is the 68rfe. The 6spds were fun and I kinda miss them but I am really diggin' the auto fo the reasons mentioned before. The whole reason I got the auto in this one is because we take the truck on road trips and the wife isn't comfortable driving a manual. My parents live 1100 miles away and it sucks driving 18 hrs by myself. this way I don't have to do all the driving!

and the truck is definetely quicker! My dragstrip time with the 07 is within . 3 of what I was getting out of the '03 with 500+ hp and smaller tires.

the only thing that sucks about the auto is the cost to build it to hold high hp.

 

[SStrano]

The misunderstandings about which trucks have an "exhaust brake" comes from the fact that none of them actually have an exhaust brake.



Yes, that's what I said. No ISB6. 7s have an exhaust brake in the way we formerly thought of an exhaust brake.



All ISB6. 7 engines have a variable geometry turbocharger which, when it closes the nozzle, performs the identical function that an external exhaust brake formerly performed when one was added to the ISB5. 9 engine as an aftermarket accessory.

It corks the exhaust, so it is--indeed--an exhaust brake. Just one that operates differently than what most are used to... .

 

[wiley75]

The new six speed automatics are well designed with good gear spacing, automatic activation of the exhaust braking feature for engine braking when towing, and are far more durable than the six speed manual with dual mass flywheel.

Your comment about durability. Is that fact or opinion? I've heard that the stock clutch that comes with the G56 is in fact marginal. But I've heard that the transmission itself it nearly bullet proof. So far the 68RE is proven to be a really tough transmission but so is the G56, and it's been out for much longer.



To the OP, the exhaust brake (VGT) works VERY nicely with the manual transmission as well. Don't get too hung up on the 650 vs 610 lb ft of torque thing. Remember that it's hard to keep an auto in lug at 100% throttle because it'll just downshift to protect itself. With the manual you can obviously do that. So at the end of the day you don't really care about what the flywheel torque is. You care about how much power you are putting down on the asphalt. Numbers can be deceiving in cases like this. Just my opinion

 

[RDHamill]

I had an '07 with the auto, and now an '08 with the manual. While my preference is the manual, the auto is a great transmission. It shifts smooth, and has great ratio spacing. I'm not a fan of the closed throttle downshift. With 3. 73:1 axle gears, the engine is just off idle at road speed. It all ended when the oil pump in the transmission sheared the input shaft, one dead trans. Truck got another one from a wreck. Then last January ( when the deals were fantastic) I traded for the manual, which is also a great truck.
My opinion after having owed both is, both are great, you can buy your truck with whichever trans type you like, and be very happy with it

 

[DPrew]

I have an 02' and 06' with the six speed. I thought I would do another six speed in my 09' but it seemed liked it was hard to shift and keep in the power. It almost felt like as I shifted the rpm's dropped just enough that the emissions constrictions cut the fuel back and caused some lag.



My 09' 3500 4x4 is faster off the line then my 500 horsepower 02'. It makes me wonder just how blazing fast my 02' would be with an auto.