99 Dodge 2500 Diesel Rear End - Montana Owners Club

av2pilot · 10-23-2006, 09:01 AM

We just picked up our new 3400RL and LOVE it. My question is that I've got a 3.54 rear end right now and when I towed it home (I live in Florida.....FLAT) it did just fine. I was slow starting out, but once up to speed it was running 60mph at about 1700rpm in overdrive w/no down shifting required( I turned the OD on after we got up to speed). I ordered a 4.10 gear and pinion and haven't put it in yet and would like some feedback from you experienced RVers! Can you tow in OD on the highway, what kind of rpms are you turning at 60-65, what kind of fuel mileage are you getting? I appreciate the help and hints! I should have done the profile signature thing first I guess!

Cat320 · 10-23-2006, 12:31 PM

Welcome to the forum.

I looked at Dodge and Ford before I got my D/A dually. Dodge no longer puts the 3.55 rear end in the diesel...it's either a 3.73 or a 4.10. I have a six speed with my Allison, it shifts to sixth around 58 to 62 mph and will stay there, and pull most hills with out down shifting unless they are steep. In that gear it turns about 1550 rpm. Don't know what your weights are with the older Dodge...you might be close to the GCWR with that rear end and a 3400.

Glass Guy · 10-23-2006, 02:03 PM

the main thing you want to be carefull about is letting the transmision search between high gear and overdrive, when it starts searching it will cause the trans to overheat and they don't last long under those conditions, you might want to add a trans temp gauge and keep an eye on those temps if the get to high then you might want to change to the 4.11 Good luck Roman

Ishler · 10-23-2006, 02:27 PM

Harry
I had a 96 Dodge V10 with the 3.54 when we purchased our Montana. I had a 4.10 installed to aid in the initial acceleration. the difference is about a 15% increase in engine speed, in your case you'd be around 1900-2000 which is a good spot for the Cummins. I had no impact in the gas mileage. The positive was when they were installing the gears they found the pinion bearings were about to go (used to pull a 10k Jayco) so I was glad they found it. We went to diesel with the latest truck an have the 3.73 which seems to be a good compromise pulling in the hills of Pa. and NY and the flats of the Midwest. My recommendation would be to go with the 4.10 or an aftermarket's 3.7x.

Redrover98 · 10-23-2006, 02:40 PM

Harry,
I have a '98.5 24valve 3500 dually with 410 rear end. When I town in OD I'm turning 1950-2000 rpm @ 60-62mph.If my rpms get much below 2000 it starts lugging on inclines and it will downshift. It is not good to let it hunt so I am careful to keep the rpms up. On very hilly roads,in high country or in city traffic I take it out of OD.When I'm not in OD at 60mph I'm turning 2800-2900 rpms. I towed my 1999 33' fiver from Fla to Alaska and back and never used OD.I replaced the orignal transmission at 125k only because I was going to increase the hp and torque and was afraid the tranny wouln't handle it. There is only a slight increase in mpg in OD on flat straight roads.
I do tow in OD with the new trans but I still watch the rpms.

av2pilot · 10-23-2006, 06:40 PM

Thanks for all the input guys! I think you convinced me of what I already knew....put the 4.10s in there! I'm glad to be a member of such a great group and look forward to meeting you on the road

azstar · 10-26-2006, 09:08 AM

Hi Folks,

Something that I found to be a problem is that my Dealer was putting the wrong weight oil in our rear diff. I had told the service writer that we tow a heavy load and to make sure that the right oil was beening used.

For the first year the rear diff. was growling during turns. it was the Posi clutches chattering.

I investigated and found out that my Dealer was putting the standard weight oil with the posi. additive.

Dodge has a different recomendation for "Heavy Towing". For heavy towing, it changes my spec on my 2000, from 75W-90 to 75W-140. I use either Mobil 1 or Amsoil Synthetic, and still use the additive from Dodge.

No more growling. I have measured the rear diff. cover temp when towing on a hot day and have seen the cover temp as high as 235 deg. You wouldn't want to touch that.

If we were to blow a rear diff. we'er looking at about $1000. Don't even want to think about that.

I do have the 4:10 and do tow in OD, but the load we tow is under 12K lbs.

I would recommend checking to make sure your using the proper tow weight oil with the posi additive (if you have posi) and only use the Synthetic oils. Pet. oils will go south at about 275 deg. (coking) but the Syn. oils can handle into the 300's.

Welcome aboard and Happy Camping

av2pilot · 11-05-2006, 11:50 AM

We just got back from our "shakedown" cruise and had a BLAST! The 4.10 rear end worked out great..thanks everyone for the input. I ran 60 at 2000 rpm and was getting 11-12 mpg and the truck was pulling her fine. I even passed a fellow Montana Owner out there on I-10!

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