Towing with CRD and OD?

ArmyChief · **Posted:** Tue Dec 16, 2014 6:09 pm

I know in a gas applications to keep transmission from overheating the OD was suggested to be turned off. However, since the CRD gets it's torque so low, is turning off the OD still recommended?

gmctd · **Posted:** Tue Dec 16, 2014 6:25 pm

Fairly certain the Owner's Manual indicates to turn O\D off when towing, and shifting to lower gear range as required

joelukex4 · **Joined:** Thu Sep 29, 2011 4:54 pm **Posts:** 386

If you turn O/D off you will be in 3rd gear. No way. I tow in overdrive and never had a problem. I tow with all my vehicles in O/D and never had problems. It will down shift if needed. Never lost a tranny yet.

ArmyChief · **Posted:** Tue Dec 16, 2014 6:47 pm

I'm pretty sure Keith at GDE recommended towing in third gear over a certain weight

gmctd · **Posted:** Tue Dec 16, 2014 6:51 pm

I'd say if you have BOOST, EGT, and trans temp gages, and know the difference between shutter and shudder, let your s-o-t-p dyno guide you, eh.............

ArmyChief · **Posted:** Tue Dec 16, 2014 7:01 pm

I will have them installed by then. My pants are a great diagnostic tool

Since the 545RFE is a five speed transmission..wouldn't turning off OD keep it in fourth, not third?

gmctd · **Posted:** Tue Dec 16, 2014 7:10 pm

4rth and 5th are both over-driven ratios, so turning off O\D may downshift to 3rd - I've not driven the li'l puffer since back in ought ten, so I'm not overly familiar with day-to-day considerations - I may be thinking of the big 68RFE 6-spd behind the big Ram Cummins - same 545RFE base, monsterized

Nope, I nailed it:
545RFE Transmission ratios:
Gear 545RFE
1st 3.00
2nd 1.67 upshift / 1.50 kickdown
3rd 1.0
4th 0.75
5th 0.67
Reverse 3.0

flash7210 · **Posted:** Tue Dec 16, 2014 10:20 pm

Drive it with OD on or OD off. Which ever works best for you, your trailer, and road conditions.
I turn OD off even when not towing because I like the TC lockup in 3rd. Then at 53 mph I turn OD on and let it shift into 4th.

dthdcrd · **Posted:** Tue Dec 16, 2014 11:09 pm

I tow a car trailer 4000lbs and a pop up camper 3000lbs all summer long. At least three weekends a month. Have the euro torque converter, GDE hot tune, GDE trans tune and ARP studs. Always tow in OD. Anticipate the hills. Squeeze on the throttle to bring the boost up before you get into the hill. Rarely do I turn the OD off. Only when I'm on a long ascending winding hill 45 mph or so do. I turn off the OD. Then I just hit the button hold a steady speed and await to level off. Then turn the OD back on. Keep in mind towing at 70 mph give or take puts the motor close to maximum torque in top gear. So anticipation and knowing when to squeeze on the throttle just before it kicks down is key. You can hold 70 mph 20 psi boost and 900 degree post turbo egt up a long hill on the highway all day doing this, in OD. I've done it many times. It's the sweet spot. 180k been towing and using this method since 40k.

mass-hole · **Posted:** Wed Dec 17, 2014 2:10 am

Turning od off does in fact drop to third and you will be spinning the motor pretty fast at highway speeds

papaindigo · **Posted:** Wed Dec 17, 2014 9:07 am

IMHO there is no nice simple "clean" answer. Depends on too many variables (load in vehicle; weight of trailer; terrain; wind; strength of torque convertor; etc). The 1st 3 probably matter the most. In the real world - 06 CRD with OEM torque converter and GDE EcoTune; 2 adults; fully loaded back seat and rear cargo area; kayak on top; fully loaded 5X8 U-Haul behind; major 4-lane roads; no major hills (I-10 AZ to North FL and various from N. FL to mid-NE) towed in O/D and cruise at 62-65mph with no problem. Don't let cruise control speed on longer hills instead use go pedal to ramp up speed a few mph before grade and to keep rpms up will prevent down shifting. In the entire cumulative 3,300 miles 2 very minor shudder episodes within 10 miles of each other that instantly stopped when I briefly flipped O/D off (coldish engine and I forgot to anticipate a small hill - should have let cruise drop a gear instead of trying to catch dropping speed late with the go pedal).

Heavier loads more grade change then yes keep O/D off in hilly areas. On flat, say I-70 across the plains leave O/D on

joelukex4 · **Joined:** Thu Sep 29, 2011 4:54 pm **Posts:** 386

In the small hills of Wisconsin towing a 3500# boat at 70mph no problem but didn't use cruise so I had better control of the "go" pedal. It was 95F that day and thought it would be better to keep the AC off. Up to a 2000# trailer set the cruise and forget it. No issues ever, GDE Eco tune, original TC.

OneCheekRider · **Posted:** Wed Dec 17, 2014 1:02 pm

I always leave OD on when I tow. However, the last big trip I did with my ~2500lb trailer on a steep incline, the temp gauge moved from one tic left of center to one tic right of center. I was in 5th hovering right around 60mph. I'm surprised it didn't drop into 3rd automatically. Temp gauge went back to normal once it leveled out. Been wondering if I should take it out of OD in that instance.

ArmyChief · **Posted:** Wed Dec 17, 2014 1:08 pm

Thanks all..I did install the larger capacity, finned cooling PML transmission and differential pans.

amslube · **Posted:** Wed Dec 17, 2014 6:34 pm

Towing with OD off will keep the RPMs up and EGTs down. For an inexperienced diesel tower the only safe way to tow is with OD off or install an EGT gauge and keep an eye on temps. When EGTs start climbing above 1300 degrees then it's time to drop to a lower gear. EGTs will climb rapidly pulling a load up a grade at lower RPMs.

Towing with CRD and OD?

Who is online