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 Post subject: Is there any way to make this tranny downshift?
PostPosted: Tue Jun 30, 2020 3:38 pm 
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I’d sure love access to 4th and 3rd gears for downhills. My daily commute involves a brake burner section that really benefits from using 3rd gear in most cars. Second is a little low for this. Also trailering on faster roads I’d like to have 4th lock for sure. Is there any way to mod this?

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 Post subject: Re: Is there any way to make this tranny downshift?
PostPosted: Tue Jun 30, 2020 5:16 pm 
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First off, everything in this transmission is controlled by the TCM, it is a full electronic over hydraulic transmission.
Depressing the OD Lockout button on the side of the gearshift will lockout 5th gear & 5th gear TC lockup and force the transmission to top out in 4th gear but it will still allow TC lockup in 3rd & 4th. At least that is what I have observed while driving mine.
It also modifies the shift points slightly so it remains in the lower gears a little bit longer during upshifts.
I'm no expert on this transmission; some others may have a better description of its function.

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 Post subject: Re: Is there any way to make this tranny downshift?
PostPosted: Tue Jun 30, 2020 8:20 pm 
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The overdrive lockout was always described as locking out both 4th and 5th gear on the CRD, since they are both overdrive gears.

Pretty sure Keith from GDE comfirmed this is how it worked way back when or even GMCTD when he was here.

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 Post subject: Re: Is there any way to make this tranny downshift?
PostPosted: Wed Jul 01, 2020 1:22 am 
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Okay that’s cool at least but I’d still love to have third it would help a lot on my commute

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Future; rear bumper, true tracs, tank fuel pump, webasto heater


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 Post subject: Re: Is there any way to make this tranny downshift?
PostPosted: Wed Jul 01, 2020 6:03 am 
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Pushing the OD-off button will leave you with 1st, 2nd, and 3rd gears.
OD-on adds 4th and 5th.

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 Post subject: Re: Is there any way to make this tranny downshift?
PostPosted: Wed Jul 01, 2020 10:45 pm 
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flash7210 wrote:
Pushing the OD-off button will leave you with 1st, 2nd, and 3rd gears.
OD-on adds 4th and 5th.

I’m pretty sure that’s not true on mine. My Jeep turns about 1100rpm going downhill do off

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Future; rear bumper, true tracs, tank fuel pump, webasto heater


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 Post subject: Re: Is there any way to make this tranny downshift?
PostPosted: Thu Jul 02, 2020 9:22 am 
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Jett wrote:
flash7210 wrote:
Pushing the OD-off button will leave you with 1st, 2nd, and 3rd gears.
OD-on adds 4th and 5th.

I’m pretty sure that’s not true on mine. My Jeep turns about 1100rpm going downhill do off

When you push the button, the OD-off light should be lit on the instrument cluster.
If the light doesn't come on then the button isn't working.
If you are not feeling the downshift maybe its because the transmission is already in 3rd.
Engine braking from downshifting is relative to gear selection and vehicle speed.
If you are at or below 25mph and pull the shifter down into 2nd, you'll feel it. Although sometimes there is a delay. (I do this frequently)

The factory transmission shift pattern is like this:
OD-on:
2nd @ 10mph -> 3rd @ 20 -> 4th @ ~40 -> 4th +TC lockup @ 51 -> 5th +TC lockup @ 61

OD-off:
2nd @ 10mph -> 3rd @ 20 -> 3rd +TC lockup @ ~40

Note: you usually cant feel the upshift into 2nd and TC lockup feels like a shift into a higher gear.

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Yeti stage 4 ECU tune. Straight pipe exhaust. DIY intercooler hoses.
Aftermarket intercooler
Fixed Flex Fan and modified factory 190F thermostat
Replaced cylinder head (cracked) at 160,000 miles + ARP studs
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 Post subject: Re: Is there any way to make this tranny downshift?
PostPosted: Thu Jul 02, 2020 11:53 pm 
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flash7210 wrote:
Jett wrote:
flash7210 wrote:
Pushing the OD-off button will leave you with 1st, 2nd, and 3rd gears.
OD-on adds 4th and 5th.

I’m pretty sure that’s not true on mine. My Jeep turns about 1100rpm going downhill do off

When you push the button, the OD-off light should be lit on the instrument cluster.
If the light doesn't come on then the button isn't working.
If you are not feeling the downshift maybe its because the transmission is already in 3rd.
Engine braking from downshifting is relative to gear selection and vehicle speed.
If you are at or below 25mph and pull the shifter down into 2nd, you'll feel it. Although sometimes there is a delay. (I do this frequently)

The factory transmission shift pattern is like this:
OD-on:
2nd @ 10mph -> 3rd @ 20 -> 4th @ ~40 -> 4th +TC lockup @ 51 -> 5th +TC lockup @ 61

OD-off:
2nd @ 10mph -> 3rd @ 20 -> 3rd +TC lockup @ ~40

Note: you usually cant feel the upshift into 2nd and TC lockup feels like a shift into a higher gear.


No TC lock in 1/2/3 in od but when od off it locks in third?

All I know is my car is turning 750RPM coming down the hill and I’d like to turn some revs but shifter in 2nd brings up too much rev. I guess it’s possible that there isn’t a gear between them but I don’t think so.
Also, I’d read that there’s actually 2 second gears on this tranny somehow. They were close to same rpm. They even called it like second hi and lo.

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2005 crd limited, tinted, OME lift, falken wildpeak 245/75-16, Suncoast, Transgo, Chevy fan+clutch, 195° Stat, Derale tranny cooler, Provent, Stage 2 tune, EGRdelete, Cat delete, Viscous heater delete, V6 airbox, Tow package, tow brakes, switchblade key, DIY roof rack, Front bumper,
Future; rear bumper, true tracs, tank fuel pump, webasto heater


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 Post subject: Re: Is there any way to make this tranny downshift?
PostPosted: Fri Jul 03, 2020 1:38 am 
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Joined: Mon Mar 24, 2008 10:26 pm
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Yes no lockup in 3rd unless OD is off.

There is 2nd gear and 2nd gear prime. One is for upshifts and one is for downshifts.

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SAMCO Sport hoses @ 48500 km
Goodyear Wrangler Duratrac LT225/75R16


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 Post subject: Re: Is there any way to make this tranny downshift?
PostPosted: Fri Jul 03, 2020 8:04 pm 
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So which gear does it give you when you select second on the stalk? I did my commute again today and observed the gears a little closer. So my choice when descending the hill is either second which turns 2500 or D with OD off, which gives about 900 rpm. So you can see I really want the missing gear that gives me about 1800.
Do you know which second the stalk 2 position gives in a descending situation?

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2005 crd limited, tinted, OME lift, falken wildpeak 245/75-16, Suncoast, Transgo, Chevy fan+clutch, 195° Stat, Derale tranny cooler, Provent, Stage 2 tune, EGRdelete, Cat delete, Viscous heater delete, V6 airbox, Tow package, tow brakes, switchblade key, DIY roof rack, Front bumper,
Future; rear bumper, true tracs, tank fuel pump, webasto heater


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 Post subject: Re: Is there any way to make this tranny downshift?
PostPosted: Fri Jul 03, 2020 8:05 pm 
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I guess other options include differential gearing changes or just not worrying about it and smoking my brakes which is probably fine too.

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2005 crd limited, tinted, OME lift, falken wildpeak 245/75-16, Suncoast, Transgo, Chevy fan+clutch, 195° Stat, Derale tranny cooler, Provent, Stage 2 tune, EGRdelete, Cat delete, Viscous heater delete, V6 airbox, Tow package, tow brakes, switchblade key, DIY roof rack, Front bumper,
Future; rear bumper, true tracs, tank fuel pump, webasto heater


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 Post subject: Re: Is there any way to make this tranny downshift?
PostPosted: Fri Jul 03, 2020 9:19 pm 
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Manually pulling the shifter down to 2 gives you 2nd gear. Not 2nd “prime.”
With the CRD TCM programming, I can’t think of any situation where it would shift into 2nd prime.

2500 rpm is not over revving the engine.
It may not feel comfortable but won’t hurt anything.

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Provent, intake elbow, and EGR delete. 5 volt bosch glow plugs
Yeti stage 4 ECU tune. Straight pipe exhaust. DIY intercooler hoses.
Aftermarket intercooler
Fixed Flex Fan and modified factory 190F thermostat
Replaced cylinder head (cracked) at 160,000 miles + ARP studs
2.5 inch lift, JBA upper arms, 235-85-16 tires.


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 Post subject: Re: Is there any way to make this tranny downshift?
PostPosted: Sat Jul 04, 2020 12:41 pm 
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I realize it’s not harmful but is too much engine braking and as you say, not comfortable. I’ll just smoke the brakes I guess. Sigh. I’m really not a good automatic driver.

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2005 crd limited, tinted, OME lift, falken wildpeak 245/75-16, Suncoast, Transgo, Chevy fan+clutch, 195° Stat, Derale tranny cooler, Provent, Stage 2 tune, EGRdelete, Cat delete, Viscous heater delete, V6 airbox, Tow package, tow brakes, switchblade key, DIY roof rack, Front bumper,
Future; rear bumper, true tracs, tank fuel pump, webasto heater


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