Surprised to find that I rarely run in 6th gear

Topic: Surprised to find that I rarely run in 6th gear - what gear do you run in? (Read 2059 times) previous topic - next topic

Surprised to find that I rarely run in 6th gear - what gear do you run in?

August 01, 2014, 02:40:37 pm

On my 1996 FT, the transmission displayed the current gear I was in. Virtually always when running along at 60mph or so, I was running in 6th gear. No surprise, just as expected.

With my "new to us" 2003 FT we got last summer the current gear is not displayed, so I have had to wait until I got my Poor Man's Silverleaf working to know what gear I was in. Much to my surprise, while running along at my normal 60mph or so, I find I am in 5th gear. In the recent drive from Palm Springs to Bend, I only saw 6th gear appear on a couple of occasions when going down hill.

So, it makes me wonder what gear other folks are running in. Any feedback would be helpful.

I read on another forum that the engine ecu has a max speed setting that affects when the transmission shifts to 6th. Anybody have any info on that fact or fiction?

Jim

Re: Surprised to find that I rarely run in 6th gear - what gear to you run in?

Reply #1 – August 01, 2014, 03:05:43 pm

Mine does the same as Dave. DAN

Re: Surprised to find that I rarely run in 6th gear - what gear to you run in?

Reply #2 – August 01, 2014, 03:07:01 pm

On my 1995 U320 M11, I am in 6th at 52 or 53 mph. Cruise all at 55 mph in 6th but I am usually faster.

Re: Surprised to find that I rarely run in 6th gear - what gear to you run in?

Reply #3 – August 01, 2014, 03:22:42 pm

Quote from: Dave M – August 01, 2014, 02:58:34 pm

No idea about the rest of the world, my setup hits 6th at about 62 mph on a easy flat road, will hold 6th down to about 58 mph before down shift to 5th.
Never been any issues.

Ditto. But will be interesting to see if it responds the same after my rebuild, don't see why it should change. Time will tell.
Roland

Re: Surprised to find that I rarely run in 6th gear - what gear to you run in?

Reply #4 – August 01, 2014, 03:23:56 pm

mine is the same as Rudy's. Around 52 mph.

Mark

Re: Surprised to find that I rarely run in 6th gear - what gear to you run in?

Reply #5 – August 01, 2014, 03:27:29 pm

Jim, like you, it took us about 3 months to discover that.

I checked with Pacific Power Products in Ridgefield to see if the shift point could be changed to 57 or 58. They advised against it. I never checked further. I set cruise to 61 and it shifts to 6th on flat road; this always worries me when driving in CA though.

Re: Surprised to find that I rarely run in 6th gear - what gear to you run in?

Reply #6 – August 01, 2014, 03:33:29 pm

Jim, are you sure of the mode the transmission is in. Maybe that would change the shift point for sixth gear. Mine defaults to econ mode but I know others default to power mode. Just a thought.

Mark

Re: Surprised to find that I rarely run in 6th gear - what gear to you run in?

Reply #7 – August 01, 2014, 05:09:49 pm

That sounds about right if you are doing 55. I have the 8.3 and 5.13 gears and mine will go in 6th at 55-59mph on flat. This is too low because at 65-70 I'm running the engine way too fast.

6th gear is a double over-drive on the allisons. I feel the final gearing should be made so that 6th gear is only used on the highway at crusing speeds (60-65mph +).

Re: Surprised to find that I rarely run in 6th gear - what gear to you run in?

Reply #8 – August 01, 2014, 05:16:33 pm

Our '03 U320 also needs to be around 61-63 mph to shift to 6th and stay there on the highway (at around 1350 rpm).

In 6th at 62 mph or 5th at 57 mph no real difference in fuel economy (in fact, may be slightly better at the lower speed and that's like attributable to wind resistance).

Re: Surprised to find that I rarely run in 6th gear - what gear to you run in?

Reply #9 – August 01, 2014, 05:32:22 pm

Ours is the same as Michelle's, have found that at peak speed in 5th gear, we get the best MPG. Shifts to 6th gear right around 61-62 MPH, RPMS drop down and you are putting more of a load on the eng.

Re: Surprised to find that I rarely run in 6th gear - what gear to you run in?

Reply #10 – August 01, 2014, 05:56:54 pm

How fast do ya'll normally set the cruise control at?

Re: Surprised to find that I rarely run in 6th gear - what gear to you run in?

Reply #11 – August 01, 2014, 06:32:24 pm

Into 6th @ about 61. Usually set cruise @ 63.

Re: Surprised to find that I rarely run in 6th gear - what gear to you run in?

Reply #12 – August 01, 2014, 06:40:52 pm

I am like Dave too. 62 into 6th and down to 59 or so. I did do an experiment this fall and drove out to Iowa at 55 as a max speed. I got better fuel mileage but it added a day for about 3/10ths. It added a day to my trip and that was ok too but last trip I moved back to 62-63mph.

Re: Surprised to find that I rarely run in 6th gear - what gear to you run in?

Reply #13 – August 01, 2014, 06:44:31 pm

I'm changing gearing so I can do 65-70 on flat at a lower RPM....I have to do some figuring but I'd thinking 1500-1600 around 65.

Re: Surprised to find that I rarely run in 6th gear - what gear to you run in?

Reply #14 – August 01, 2014, 06:57:20 pm

I often drive detween 55 and 60 and vmspc reports 6th gear. But mine is a u295.

Re: Surprised to find that I rarely run in 6th gear - what gear to you run in?

Reply #15 – August 01, 2014, 07:14:37 pm

Hi Jim,
Our 1997 U320, M-11, 4060R trans, does just as Dave M's. Never into sixth gear until 62 mph.
Raymond

Re: Surprised to find that I rarely run in 6th gear - what gear to you run in?

Reply #16 – August 01, 2014, 11:33:40 pm

My 400 ISL is in 6th around 54 or thereabouts.

Re: Surprised to find that I rarely run in 6th gear - what gear to you run in?

Reply #17 – August 02, 2014, 08:18:59 am

Mine is around 53 to 55 in econo. 60 in power.. 1500 rpm at 69 to 70 . with cruise on at 1600 rpm is
73 to 74 with toad and full of fuel and water. I will get 7.85 mpg over 400 miles or so going through Alabama. I'm very happy with that.

Re: Surprised to find that I rarely run in 6th gear - what gear to you run in?

Reply #18 – August 02, 2014, 10:25:18 am

Quote from: Rudy – August 01, 2014, 03:07:01 pm

On my 1995 U320 M11, I am in 6th at 52 or 53 mph. Cruise all at 55 mph in 6th but I am usually faster.

You and I have a 3.91 rear axle ratio I think. The newer m11's are geared lower at 4.31?

Mine shifts in sixth at 55mph I think.

The shift points are adjustable by a shop.

Torque peak is 1350 rpm on the 450.

Needs to be in 6th at the 60 I would think.

Different tire size?

Re: Surprised to find that I rarely run in 6th gear - what gear to you run in?

Reply #19 – August 02, 2014, 10:44:16 am

I have been interested in posts such these for some time but find it hard to get my arms around the data.

I have a 300hp mech. Cummins 8.3
Someone else has a, say, 450 Ixx
Some one has a 1,000 hp electric...

I would think some kind of tabulation by engine might be useful.
Along the same vein, I would like to find a torque curve (or something I can maybe understand) to give me a clue about rpm ranges I can live with and when I should start screaming (before the engine preferably).

I cruise at 62 at 1850 rpm. The transmission has been in 6th since 1500 probably.
When I gear down to descend a hill do I worry at 2200, 2400, 2600,..?

Just another morning full of finding things on the Forum to worry about..

Re: Surprised to find that I rarely run in 6th gear - what gear to you run in?

Reply #20 – August 02, 2014, 11:03:05 am

Quote from: Raymond Jordan – August 01, 2014, 07:14:37 pm

Hi Jim,
Our 1997 U320, M-11, 4060R trans, does just as Dave M's. Never into sixth gear until 62 mph.
Raymond

Then ours or yours was reprogrammed I think. 55 mines in sixth.

Re: Surprised to find that I rarely run in 6th gear - what gear to you run in?

Reply #21 – August 02, 2014, 12:00:05 pm

The height of that Phenix will kill your fuel economy. As long as you are having it custom built, maybe 320 like height and a GV nose would be in order.

Re: Surprised to find that I rarely run in 6th gear - what gear to you run in?

Reply #22 – August 02, 2014, 05:32:49 pm

Howdy Elliot

Quote from: TheBrays – August 02, 2014, 10:44:16 am

Just another morning full of finding things on the Forum to worry about..

Boy, ain't it the truth!!! I think I'll go for the 15yr single malt..
Dave A

Re: Surprised to find that I rarely run in 6th gear - what gear to you run in?

Reply #23 – August 02, 2014, 05:44:28 pm

Quote from: Michelle – August 01, 2014, 05:16:33 pm

Our '03 U320 also needs to be around 61-63 mph to shift to 6th and stay there on the highway (at around 1350 rpm).

In 6th at 62 mph or 5th at 57 mph no real difference in fuel economy (in fact, may be slightly better at the lower speed and that's like attributable to wind resistance).

Seriously considered dropping down to 5th gear and 55mph + - heading into fierce headwinds in Texas two weeks ago.

Re: Surprised to find that I rarely run in 6th gear - what gear to you run in?

Reply #24 – August 02, 2014, 07:26:12 pm

Quote from: TheBrays – August 02, 2014, 10:44:16 am

I have been interested in posts such these for some time but find it hard to get my arms around the data.

I have a 300hp mech. Cummins 8.3

Along the same vein, I would like to find a torque curve (or something I can maybe understand) to give me a clue about rpm ranges I can live with and when I should start screaming (before the engine preferably).

I cruise at 62 at 1850 rpm. The transmission has been in 6th since 1500 probably.
When I gear down to descend a hill do I worry at 2200, 2400, 2600,..?

Just another morning full of finding things on the Forum to worry about..

Here is the information from Cummins Quickserve on my 300 hp 8.3, you can get the same info on your engine by registering on the Cummins website. As I read it, peak torque and maximum efficiency is at 1300 RPM, a max governed hp of 275 @ 2400, High Idle is 2710 rpm above which you are in peril. Little foggy on just what "high idle" is, maybe someone more knowledgeable can explain it.

Electronic Parts Catalog - Option Detail
Option   Group   Graphic   Film Card   Date
Cart   Ref No   Part Number   Part Description   Required   Remarks
FP97356
Fuel Pump

Fuel Pump...(More)

Engine Family: C Series

Engine Cylinders: 6

Advertised HP: 300 @ 2200

Governed HP: 275 @ 2400

Torque Peak (lb-ft): 820 @

1300

Fuel Pump Type: Inline

Pump Manufacturer/Model:

Bosch P7100

High Idle: 2710

Governor Type: RQVK

High Pressure Tube ID (mm):

1.8

Boost Control Provided: Yes

Shutdown Device: Electrical

Compatible Fuel Rating - FR:

9748

CPL: 2102

Certified by: EPA

CARB Taiwan EPA

Certification Year: 1997

Certification Status:

Approved

Governor Break RPM: 2475

Governor Regulation (%): 9.5

Affiliate Notice