Engine/Transmission (1998.5 - 2002) Tires, Towing & RPMs...Gears? HELP!

[klaybus]

1999 Ram 2500 Auto trans 4. 10s & 295x75x16 tires I see the following at 60 mph. Looking for real life numbers of members running a 2nd Gen 24V Ram with 4. 10s running 265x75x16 tires. What kind of rpms at 60 mph are you seeing both in & out of OD?



Clay



2625 rpms at 60 mph (295X75X16)

1800 rpms at 60 mph in OD (295X75X16)

 

[SnoKing]

Klay, on the big hills take it out of OD and turn the RPM's up. I can run up to 63 MPH or so with 265's and 4:11's. I am going of a 6 or 7k trip this fall and have towed to the ocean and back with the new PDR35 and think I have it right now. SNOKING

 

[klaybus]

Sno... .

What are your rpms in OD at 60? How fast can you go in 3rd direct?



Clay

 

[rweis]

I have stock tires, 4. 10 ETC, DD2's, KSB1-B.



I try to run at 2000 rpms or very close to that. If the "hill, load, altitude etc" will not do that in OD (about 63 mph) then take it out of OD and run at 2000 rpms (about 45 mph). With the 4. 10 and out of OD and 2000 rpm it tows my 13k 5er just fine through anything (about 45 mph). I have a DTT and if I had to I could go to 2nd lockup if I could not maintain 45 mph because of road conditions. I never have had to do that and do not know what 2nd lockup 2000 rpms would be in mph.



Before I went to 4. 10 from 3. 54 I ran out OD when ever towing and have run at 2400 rpm (about 60 mph as I remember) for hundreds of miles. I personally would not go much over 2400 for long periods of time. You probably could, but I tend to be on the conservative side.



Bob Weis

 

[klaybus]

I have stock tires, 4. 10 ETC, DD2's, KSB1-B.



I try to run at 2000 rpms or very close to that. If the "hill, load, altitude etc" will not do that in OD (about 63 mph) then take it out of OD and run at 2000 rpms (about 45 mph). With the 4. 10 and out of OD and 2000 rpm it tows my 13k 5er just fine through anything (about 45 mph). I have a DTT and if I had to I could go to 2nd lockup if I could not maintain 45 mph because of road conditions. I never have had to do that and do not know what 2nd lockup 2000 rpms would be in mph.



Before I went to 4. 10 from 3. 54 I ran out OD when ever towing and have run at 2400 rpm (about 60 mph as I remember) for hundreds of miles. I personally would not go much over 2400 for long periods of time. You probably could, but I tend to be on the conservative side.



Bob Weis

Thanks Bob! Thats exactly the info I wanted\needed to know. People seem to think 3. 5s will tow just fine & they don't! I've been running 285s & 295s which puts me at 2250 or so at 62 mph. That would work fine until I hit a winding curve & was unable to maintain lockup & then the EGT's & warming transmission made for a miserable trip!

Since going to the 4. 10s the throttle is much more responsive but... 1800 at 60 mph in OD & 2625 out of OD at 60 mph... . Gotta dump the 295's & it appears I need to go to some 265s...



Thanks for the heads up!

Clay

 

[rweis]

I'm going to sort of address what I think is another piece of this towing pie - the turbo.



Mine is a KSB1-B (not waste gated because the seller thought I would never get to a point that the waste gate would open, should have been a clue!, not enough fuel (but I don't need any more fuel than I already have with DD2's)) and I am convenced it is too big for the DD2's. I have to keep it up around 2000 rpm to get good towing ability (you mentioned 1800) in OD. I am going to take my S300 to a local turbo shop and I think the HTT HTB(x) 57/12 or 62/12 is going to be a much better sized turbo. I do not know what my xx/xx is but I would bet something like 62/14. I have very little low end spool ability. Mine has to be above 10# to even think about spooling. I personally do not care about the lag. I would like to be able to be at 1600 and start to get it spooling. I rarely go over 28# but can go to about 34# max, not interested to be up in the 40# and jeprodize the head gasket.



I bought the KSB1-B because there were pics of the shaft and it's shaft was twice as big to what a HX40 shaft was (and there was some broken HX40 shafts happening then) and I had zero idea about xx/xx (only have slightly more idea now). I think that there might be a possibility that the front and back ends of the turbo might be able to be changed out to get me closer to what I should have and have the big shaft as well (again, I do not care anything about the lag part to be able to have a reliable "heavy duty" shaft).



Just some thoughts that might blend into the towing equation.



I never got to the point of changing different tire sizes like you did.



Bob Weis

 

[klaybus]

Well I just borrowed (2) 265x75x16 tires. One from my brothers truck & the other from my neighbors truck. Both RAM 2500 CTD 6 speeds. Getting ready to swap them out now. Hoping to see a 200 rpm increase at 60 mph. I'll post the results in a bit.



Clay

 

[John - K5AWO]

I'm running a dually 98. 5 with 4. 10s and 255 tires. (can't go bigger, they touch sidewalls) In OD it runs at 65 mph at 2100 rpm and the stock turbo is very playful. Just touch it and go. It will pull to 2500-2600 without any trouble at all. Like Bob Weis, I too am not of the "you gotta stay in OD" mentality. If it has to come out of OD, then I just let it plunk along at 2100-2200 and live with it. Those hills are not all that long and percentage wise, they just do not make up much of your towing miles.

Right now, my truck is being worked on out in San Diego by my son. When I get it back, I hope to be impressed as the stuff in my signature is being added to it. Being able to lock up the TC anytime I want it will be nice, as will being able to keep it locked when it is out of OD. That will really be nice as I can pull the mountains in 3rd lockup and keep the transmission cool.

 

[klaybus]

Well I just borrowed (2) 265x75x16 tires. One from my brothers truck & the other from my neighbors truck. Both RAM 2500 CTD 6 speeds. Getting ready to swap them out now. Hoping to see a 200 rpm increase at 60 mph. I'll post the results in a bit.



Clay

Well, so much for trying out the 265s! The rims off an 01 & 02 won't go on over my 99s rear brake drums. I've got a set of pretty much worn out 265s I'm going to have mounted tomorrow & then go for a quick freeway run. If they turn the 2000-2100 that it sounds like they should I'll be picking up (4) new Michelin LTX M\S 265x75x16E's... Four days to vacation & hopefully this makes it all go well.



Clay

 

[SnoKing]

Clay, with 265's I turn 2K and do about 63 MPH. At 19K combined weight, I can run most freeway hills. In the mountains you can go to 3rd and run up to 2600-2700 and pull until the pyro says let up. I have not been able to test the PDR35 except for the one trip to the ocean, but it seems to have solved my EGT issues.



NOT BE AFFRAID OF RPMS in 3rd on the big hills. Or you can settle into 2000 RPM in third and let it climb, as it will climb just about anything at that.



BTW, I down shift out of OD as soon as I can not hold 2000 RPMs.



SNOKING

 

[jeepit]

I am in need of new tires soon. I was thinking of 285's?. ? 265's now. I don't want to lose towing power. My heaviest load is when I have Lance slide in camper (2000lbs)and the Jeep on trailer apprx 6500lbs. Specs below...

 

[SnoKing]

Clay what are you running for intake and exhaust?

SNOKING

 

[Boondocker]

I am in need of new tires soon. I was thinking of 285's?. ? 265's now. I don't want to lose towing power. My heaviest load is when I have Lance slide in camper (2000lbs)and the Jeep on trailer apprx 6500lbs. Specs below...

You will lose "towing power" going from 265 to 285 tires. With the 6-speed and 3. 54 gears, I find 265 diameter to be a perfect match for towing at freeway speeds - around 55 mph in 5th gear, around 65 mph in 6th gear. With the motor sweet spot around 2100 rpm, that puts me at 72 mph, a little too fast for my towing speed preference. With taller tires, I would never see that sweet spot. Most of the time, I try to keep the rpm in the 1900-2000 zone. That puts the speedo between 62 and 65 mph and keeps the engine and exhaust temps at comfortable levels. This is based on trips like last week's, grossing about 17K, air temp 105, A/C on. Man I love this truck!



Regards,

Neil

 

[klaybus]

Clay what are you running for intake and exhaust?

SNOKING

Sno,

AFE PG7 Intake & Rips 4" exhaust. Got the Michelin LTX M/S 265X75X16s installed today & expect much more better results. Leaving Thursday but only pulling the boat so not much of a test... . Probably around #3000. I will get to test it throughly on the 12th of August pulling the 5vr Westbound out of Vantage going over Snoqualmie pass.

Also changed the thermostat, coolant, oil, fluids etc. Also removed the radiator & cleaned it. 3 pics attached.

1) new tires

2) radiator during cleaning

3) radiator cleaned



Clay

 

[SnoKing]

Westbound out of Vantage is a good test, HOT and LONG and easy to get boxed in and knocked down a gear. Takes a good setup to recover speed if that happens.



I think you will be happy now. Another good test hills is South out of Ellensburg to Yakima.



SNOKING

 

[jeepit]

You will lose "towing power" going from 265 to 285 tires. With the 6-speed and 3. 54 gears, I find 265 diameter to be a perfect match for towing at freeway speeds - around 55 mph in 5th gear, around 65 mph in 6th gear. With the motor sweet spot around 2100 rpm, that puts me at 72 mph, a little too fast for my towing speed preference. With taller tires, I would never see that sweet spot. Most of the time, I try to keep the rpm in the 1900-2000 zone. That puts the speedo between 62 and 65 mph and keeps the engine and exhaust temps at comfortable levels. This is based on trips like last week's, grossing about 17K, air temp 105, A/C on. Man I love this truck!



Regards,

Neil

Yeah, I hear ya. 265's it will be. I bought this truck new 5 years ago for towing power and mileage and I don't want to screw that up with the larger tire. I have better things to spend my $$$ on instead of re-gearing.

Thanks for being up front Neil. I appreciate it.

 

[SnoKing]

Clay, how is the truck working now???? SNOKING

 

[klaybus]

Clay, how is the truck working now???? SNOKING

Pulling the boat East-bound was pure cake! I didn't even know it was there! Shot up Vantage East-bound at 70+. Now, pulling the 5vr West-bound was a little different story. I kept it in OD at about 56-57 but water temps & EGTs we're getting a bit warm. My water temps went about 2 needle widths above 190 & EGT's hit 1150+ A couple of times. I think in the future I will probably just slow down a touch & run it in 3rd direct. It was warm outside when we passed through too. Probably about 95* outside. All in all, I'm happy with the new tire size. Performance is improved & I think my mileage might actually improve. PDR-35 may be next on the list but this past month or so I've spent a fortune on gearing & tires so I suspect it will be waiting for a while.



Clay