Towing RPM Best Practice

imclumzy · **Joined:** Fri Jun 15, 2012 11:30 am **Posts:** 48

I have just returned from a 1000 kilometer (600 mile) round trip towing near the rated capacity of the CRD. Mine's a 06 Limited with the factory tow package and Air Lift airbags. I was towing a uHaul dual-axle car transporter ~2200#, my car was another ~2300#, plus my track/camping gear ~350# and me 150# would easily put it up to the capacity.

I was driving mostly along highways and I had a question about gearing and the diesel engine. Does it matter if I tow in 4th gear at 3500RPM or 5th gear at 2000RPM? I noticed that in 5th gear if I'm steady state on the flats at around 2000RPM, on slight inclines the transmission sounds like it's slightly struggling. While in 4th gear on flats at 3500RPM it intuitively feels (from my gas vehicle experience) like it's too close the redline of 4000RPM.

I suppose my question is, what is the best practice for tow gear? Which is better, cruising at high or low RPMs? Under load, does the diesel engine care if it's spinning at lower RPMs or higher?

papaindigo · **Posted:** Thu Aug 02, 2012 12:56 pm

For what it's worth on this tow (viewtopic.php?f=5&t=69117&p=739421#p739421) we ran 60-65 in 5th/full lockup at ca. 1800 RPM with the exception of a few hills where the tranny downshifted if we negelected to add some throttle/speed prior to the incline. Of course our load was less than yours.

Generally I'd say tow in the highest gear that you can without the tranny "hunting" (constantly downshifting). In hilly terrain remember to add speed before the incline but if it's a long uphill pull feel free to drop speed and gearing to pull the grade at a lower speed but ideally in the 1800-2000 rpm sweet spot.

Running a constant 3500 rpm would make me really uncomfortable.

Also remember if you tow a lot that ATF+4 for more frequent tranny fluid changes is much cheaper than a new tranny or torque convertor.

Klem531 · **Posted:** Thu Aug 02, 2012 1:27 pm

I have just returned from a 1000 kilometer (600 mile) round trip towing near the rated capacity of the CRD. Mine's a 06 Limited with the factory tow package and Air Lift airbags. I was towing a uHaul dual-axle car transporter ~2200#, my car was another ~2300#, plus my track/camping gear ~350# and me 150# would easily put it up to the capacity.

I was driving mostly along highways and I had a question about gearing and the diesel engine. Does it matter if I tow in 4th gear at 3500RPM or 5th gear at 2000RPM? I noticed that in 5th gear if I'm steady state on the flats at around 2000RPM, on slight inclines the transmission sounds like it's slightly struggling.

Quote:

While in 4th gear on flats at 3500RPM it intuitively feels (from my gas vehicle experience) like it's too close the redline of 4000RPM

I suppose my question is, what is the best practice for tow gear? Which is better, cruising at high or low RPMs? Under load, does the diesel engine care if it's spinning at lower RPMs or higher

I'm curious to know, you state 3500 rpm in 4th? is this by means of using the overdirve button on the shifter? Cause if it is, then your in 3rd. :banghead:

imclumzy · **Joined:** Fri Jun 15, 2012 11:30 am **Posts:** 48

I believe the CRD is a 4 speed tranny with overdrive? With overdrive Off I thought I counted 4 gear changes. And when I turned overdrive On, it shifted up to 5th.

Kgeisler2010 · **Joined:** Sun Sep 04, 2011 9:56 pm **Posts:** 66

Hitting the overdrive button make it only shift to third as both 4th and 5th is a overdrive. Its kinda weird in my opinion..

Klem531 · **Posted:** Thu Aug 02, 2012 5:05 pm

Actually 4th and 5th are both overdrive gears on these strange little Italian tractors of ours. I was a little surprised to find this out myself. :dizzy:

And pushing the OD button does infact put the tranny into 3rd. :JEEPIN:

viewtopic.php?f=1&t=2830&hilit=2+overdrives When I was first looking for one of these CRD's I drove 2.5 hrs into Michigan to test drive an 05 I found for sale on Craigslist. The guy was nice and all but cars just weren't his thing. He was showing me all the in's and out's of his Libby and he pointed to the overdrive button and said to me in all seriousness "thats the turbo button"... I could barely contain myself. :ROTFL:

I said you mean the overdrive button and he got the deer in the headlights look and said no its the turbo button. Then he proceeded to tell me how he only uses the turbo button when hes passing or merging on to the highway. I ran away from that one :banghead:

warp2diesel · **Posted:** Thu Aug 02, 2012 6:01 pm

With my mods that includes a TCM that locks up into 5th lock as low as 47MPH, I only press in the OD button when I am towing a load over 5,000lbs and driving under 60 MPH. As soon as I hit 60 MPH the OD button gets placed back into the overdrive position.
Unlike the OLD diesels used in ORT trucks many years ago (pre "89 in most cases) that had fixed timing, we don't have to put up with operating our CRDs in a narrow RPM range when loaded like the old OTR diesels. For mine, anything over 1,600 RPMs is OK when I am towing a 5,000lbs-7,000lbs Trailer Load. Reving the crap out of your engine only wastes fuel and cranks up your EGT when towing a heavy load.
I never use the cruse control when climbing a hill towing or going down, it jacks up the EGT and revs the engine too high. When I hit the flatter ground or rolling hills, I engage the cruse then.

imclumzy · **Joined:** Fri Jun 15, 2012 11:30 am **Posts:** 48

Ok I'm showing my noobie-ness here ... I've only owned the CRD for a couple weeks

What is Kap's Tstat Mod and what is the "Non-F37 TCM"?

Klem531 · **Posted:** Fri Aug 03, 2012 9:38 am

imclumzy wrote:

Ok I'm showing my noobie-ness here ... I've only owned the CRD for a couple weeks

What is Kap's Tstat Mod and what is the "Non-F37 TCM"?

While I'm not 100% certain myself on The tstat mod. I believe its where guys are removing their stock sealed tstat and replacing it with an inline tstat. If you don't know yet, on our CRDs, the tstat is inside of an aluminium housing that can not be opened. On a side note. There are a couple of people offering a service where they mod the sealed housing and make it so you can swap out the tstat like any normal vehicle. The TCM or transmission control module, was modified by Chrysler under the f37 recall to deal with a large number of torque converters being destroyed by the torque generated by our libbys. In reality, junk parts were the cause and all Chrysler achieved by doing this was to neuter our tractors by reducing torque,hp and changing the shift points in the trans when in all reality, all they needed to do was replce our torque converters with one that has stronger springs. So in the previous post a non F37 tcm is one that has not been mucked up by the dealership. In warp2diesels case. I believe he is actually running a tcm out of a dodge pickup in his libby hence the non F37 statement.

papaindigo · **Posted:** Fri Aug 03, 2012 1:06 pm

imclumzy - welcome aboard and if you have not already done so read Sir Sam's NOOB guide. As to your questions:
1. Kap's tstat mod - if you are up to reading all or portions of a 35 pg post viewtopic.php?f=5&t=50940&hilit=thermostat . If not the short version is the CRD tstat is a sealed unit that as designed has to be replaced in its entirety if the $12 tstat that's sealed inside it fails. Up side is if that tstat fails it typically fails open so your engine overcools which hurts mpg but does not cause the harm overheating would produce if the tstat fails closed. Down side is the tstat part costs ca. $125 and tends to fail every 40K miles or so (FYI if your temp gauge needle when warmed up is reading less than ca. 1/2 a needle width left of straight up your tstat has failed open). Kap's mode is to crack the sealed unit open and remanufacture it to accomidate a removable upper housing so that the $12 tstat can simple be replaced if it fails (FYI my son stoutdog has one of these units). Unfortunately manufacturing is stuck as he was relocated to down under and is having 50hz overheating problems with is 60hz US lathe motors. An alternative approach that seems to work (I've participated in the discussions but for personal reasons don't plan to use this approach) is to put an inline tstat in the upper radiator hose adjacent to the OEM tstat outlet and to include a small hole in the skirt of the inline tstat to avoid any temp spikes.
2. F-37 - the 2005 original stock CRD engine was relatively high in hp/torque output and when combined with the early 2005 OEM torgue converter that had a plastic part, forget what part, destroyed those TC almost immediately. That early model TC was superseded by a somewhat beefer TC which was still marginal given OEM stock 05/06 engine power output. DCJs "solution" was not to do a recall and replace the still marginal TC with the heavy duty unit that should have been used in the first place (that heavier duty unit came out in 07 for the overseas market and is commonly referred to as the Euro TC) rather DCJ elected to a) detune the engine power a bit and b) raise the shift points on the TC by reprogramming the torque convertor module (TCM) to put less stress on that better but still marginal TC. The F-37 recall did this AND in case where the stock TC was failing a replacement (same marginal TC) TC was installed. In a few cases the F-37 was never done on a specific vehicle (simply not done or the vehicle was wrecked before the F-37 came out) or it was done but the mechanic "forgot" (really forgot or was induced to forget by the vehicle owner) to reprogram the TCM. In those cases you have a pre-F-37 TCM in the sense that its shift points are those that predate the F-37 service. These units are somewhat prized and can easily be identified in operation (FYI I used to have one) by the final shift point being ca. 58 mph instead of ca. 63 mph. The advantage being that you can get to and hold that higher gearing sooner and a lower speeds which is good for mpg.

Solution to #2 - GDE EcoTune returns engine power that F-37 took away in a manner that does not over stress that marginal TC plus does other wonderful things the improve mpg and engine life - GDE basic TCM tune returns that upper shift point to the pre-F-37 range and does other generally good things but mainly for driving at speeds under 60mph (e.g. in town or slower hwy driving)

DOC4444 · **Posted:** Sat Aug 04, 2012 7:56 am

The GDE "tow tune" allows you to actually use 4rth gear up to 70you MPH. See the recent post about GDE "tow for the details.

DOC

imclumzy · **Joined:** Fri Jun 15, 2012 11:30 am **Posts:** 48

Alright so to cut to the chase. GDE Ecotune is good for towing and costs $500. The GDE TCM tune is also good for towing.

To be safe, should I get both?

Klem531 · **Posted:** Sat Aug 04, 2012 10:03 am

imclumzy wrote:

Alright so to cut to the chase. GDE Ecotune is good for towing and costs $500. The GDE TCM tune is also good for towing.

To be safe, should I get both?

You should read my other post: TCM tune or not to TCM tune that is the question.
I asked the same thing and got alot of good responses. What it boils down to is what you wanna use your jeep for. There are 2 TCM tunes available. One helps to improve fuel economy, the other from the way it was explained to me was for towing in hilly/mountainous terrain. This tune won't help your economy because it holds 4th to 70mph if I remember correctly where as the first TCM tune returns the shift points to what was originally programmed into the jeep. Or close to it anyway. Now I spoke with Keith at GDE and the first thing he asked me was if I had the F37 done which I do. He advised that I only go with the ECO tune and not the trans tune until I upgrade the torque converter as the TCM tune adds additional torque which will cause my torque converter to shudder even worse than it all ready does.Now some members have reported no shuddering at all with the f37 but I'm one of the unlucky ones.....story of my life. Lol Do you know if you have the F37?

DOC4444 · **Posted:** Sat Aug 04, 2012 3:55 pm

IM,

If you are towing that much weight, you REALLY need the tow tune to give access to 4rth. Bouncing back and forth betwween lugging in 5th and "buzzing" in 3rd will drive you nuts, not to mention killing your trans and mileage. Regarding economy, the tow tune is the same as the "regular" except for delaying the upshift to 5th to 70. Almost all the economy gains are between 35 and 55 MPH. If you plan to cruise at say, 62, just briefly go up to 70 to get 5th, then drop back down. I believe you have to drop below 55 to come out of 5th.

Regarding an ECU tune, you should first get a solid TC installed. Towing that much weight, you are going to have a hard time "driving around" the shudder problem. I don't think the ECO will work that well to protect the TC towing 5K. Just replace the TC and go with the HOT tune for towing that heavy. We have 20K experience towing with this setup. The extra power really makes it much more pleasant.

For people who don't tow, the ECO and an old OEM TC should be fine.

DOC

Towing RPM Best Practice

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