How many of you tow in drive/over drive. Personally, I dont think its right but I have no choice w/ 4.10s. Heres my solution and im looking for input. Im lifting my truck with a 4.5"lift, and thinking of running 35,36,or 37's. What im trying to do is be able to go 60-65 in drive (2300-2500RMP).Does this sound about right?

 

I tow in the tallest gear I can. Usually this is OD. I recently towed about 8K over a mountain in OD. I can thank my PM3 for that ;D, but my EGTs were getting up there.
Under normal circumstances, with an EZ, you can tow in the "foothills" in OD with no downshifting.
The rule of thumb is if the tranny starts "hunting" you should lock out OD. This means it does not stay in OD for any length of time due to the weight and terrain.
I dunno about RPMs because I have 3.55's and it would not compare to yours well.

Chris

 

Thanks for the reply Chris. My big complaint is that Ive alcays been told/practiced that the OD bands aren't built to stand the pressure/heat of towing 3000lbs much less the 8000+ im towing. I'l admit i'm new to the diesel thing, but a auto is still an auto.
Jason

 

I don't get your speed vs rpm you posted. 2600-2700 is way high. I have 4:10's and 70 mph is around 2150-2200 rpm. If you put taller (bigger) tires on you will effectively lower the ratio. My tires are about 10% larger (roll-out) then the stockers, so my effective ratio is around 3.70.

 

Right now I have 265's and my rpm in DRIVE (3rd) is at around 2500-2600 at 55mph. Ive done the math with the taller tires and with 35's my effective gear ratio ends up around the same as 3.55s. Im hoping it will bring my rpms down to a livable range to tow at 60-65 in 3rd.
Jason

 

That does sound way high. Does your lock up convertor lock up? ???

 

Far as I can tell.

 

[quote author=dukeboys link=board=7;threadid=20289;start=0#msg190987 date=1064943193]
Right now I have 265's and my rpm in DRIVE (3rd) is at around 2500-2600 at 55mph. Ive done the math with the taller tires and with 35's my effective gear ratio ends up around the same as 3.55s. Im hoping it will bring my rpms down to a livable range to tow at 60-65 in 3rd.
Jason
[/quote]

I have 3.54 gears and 33" tires, in 3rd gear at 60-62mph, I'm turning 2500rpms. I tow in OD whenever conditions allow. I have an ATS now with the beefed up OD, but even with the stock trans I towed in OD.

 

On the flats I dont really mind being in OD, but it s when I start pulling a grade, I'd like to be out. It sounds like many of you just leave it OD, but theres alot of trany problems posted too .

 

Yeah, that's what I meant when I said "when conditions allow". I wouldn't push the OD unit too much on long/steep grades.

 

yeah, I'm feelin you 99, but I just haven't had anyone reply about my original post. rpms/gear ratio/tire size.

 

[quote author=dukeboys link=board=7;threadid=20289;start=0#msg191046 date=1064950883]
yeah, I'm feelin you 99, but I just haven't had anyone reply about my original post. rpms/gear ratio/tire size.
[/quote]

I guess I got lost in the thread also... try the calculators at the following link:

http://www.ring-pinion.com/calculato...latorsind.html

... these may help answer your question, or at least give you some ideas.

 

Thanks 99, fun little calculator to play with. Best one Ive seen. Doesn't look like its feasable w/out gettin this thing to rev to 4000 ;D Anybody,anybody ??? J/K

 

I have the 4:10's. When I tow, it's an 11,000 pound fiver, and I tow in OD unless I get pulled down below 1600 RPMs or the tranny begins to hunt. Then I punch it out. I've towed thousands of miles, and haven't had a problem. I do have the DTT TC and valve body. You might want to check out changing out your gears for the 3.55's. Might be cheaper than the new tires and rims. I've heard that the gears cost about $500.00 a differential, but that's approximate. Just a thought.

DeWain

Hey dukeboys: I just read your sig. I used to own a '74 cuda with the 340 and the "sixpack" carb setup. Sweet ride! Wish I still had it.

 

DPG- I've wanted to do the wheels/tires/lift anyways, but was trying to kill two birds..... :
Have had the Cuda for 16years and couldn't ever get rid of it!!!! Thats a project down the road.