like some thoughts on 2 speed rear axles

[AHuggard]

I very just bought a pretty much stock 93 D250 TD one owner. Has a 3. 5 rear end and standard duty automatic with under bed cooler. No engine mods but I have already installed a second battery, transmission temp gage, and a tach. Still haven't got factory manual yet. I am already well advised that the transmission is the weak link; however, the local Dodge service mamager says they have replaced the rear end 3 times in this truck. I know the prior owner and he pulled a 23ft 5th wheel camper OTR. Now, not wanting to replace the transmission, cost and I am old so I like the auto shift, and wishing to use the trucK for kicking around as well as work, it seems to me that a 2 speed rear end might be helpful. Say around 4:11 for pulling and the 3:5 ratio for normal. I am not sugesting that I would try to split shift just leave it in high or low depending on what I am doing. I am not an over the road type but I do live in the hilly part of the Kansas country. (Yes there are hills in Kansas) I could be way off base with this thought but who knows maybe one of you great and wise adventurers has done it or at least already thought about it. As with most folks wealth seems to have eluded me so the availability of remanufactured or quality used sources would be helpful in this discussion. Any one want to comment. (Your stupid! is an acceptable answer as appropriate)

Al, I love the truck, Huggard

 

[BHiggins]

In theory you have a great idea, but every two-speed rear axle I've ever seen has had a HUGE housing compared to the Dana 70. I don't know if you could fit a two speed under a Dodge without a ton of modification. There's also a question of lug pattern on the actual axles, you might not be able to use your old rims and tires.

What I have seen is an overdrive unit that bolts to the tailshaft of the transmission or transfer case. You could drop your axle ratio to 4:11 and just use the overdrive to attain the lost highway speeds. I think the overdrive unit came from a company called "Gear Vendors". Changing your ratio and adding the overdrive is probably expensive, but I think it would be cheaper than trying to get a two speed rear under your truck.



Brian

 

[ARhine]

Two speed truck axlesa are huge like stated above. Also setup for usually at least 20" truck rims. . and you need a tire that tall to keep the center off the ground

 

[AHuggard]

Brian, I forgot to mention that I have a factory overdrive already. Is the unit you refer to an add-on to the standard setup or is it just a better one to replace the one I hae. I really hadn't thought about looking out the OD to assure more pull, the overdrive could be the reason the other guy lost so many rear ends.



Al

 

[BHiggins]

It's a bolt on unit external from the transmission. If you changed your ratio to say 4:11, you would probably only get around 60 miles per hour out of the truck before the engine got into the governor. Add the external overdrive and you've got the best of both worlds, a truck geared for pulling that can still keep up with highway traffic.

As I said, they aren't cheap, but it beats trying to fit an Eaton-Fuller two speed axle in your truck. And from what I understand they aren't hard to install, but do require you have your driveshaft shortened.

 

[BHiggins]

To the moderator

Moderator,

I apologize for posting a link to an outside vendor, I realize now this may have been "over stepping" the bounds of the TDR. I am in no way affiliated with the company mentioned and simply posted it to try and help a fellow member. I have since removed the link and in the future will PM any links to specific vendors.

Again my appologies,

BHiggins

 

[TKingsbury]

This would be kinda expensive, but very do-able. Install a U. S. Gear under-drive in your truck. This will give you an extra low 1st, and the ability to split gears while keeping your existing OD cruising RPM. And if you don't want or need the low range or gear split, just leave it in direct. The cool thing about one of these units instead of say a Gear Vendor is that you can accelerate from a dead stop with it in low, and you can compression brake with it too. A Gear Vendor is actually an overdrive, so you don't get the advantage down low. Gear Vendors are programmed to come on after 35 mph, under this speed it can't be operated. The reason for this is they run off of an internal oil pump that is dependent on driveshaft speed. If the driveshaft isn't turning fast enough to make their specified pressure, it will slip and burn up. You also can't compression brake with a Gear Vendor, it will slip the clutch inside it and burn it up. I have personally never had either of these units, but know people who have had each. If it were my choice to make, it'd be a U. S. Gear under-drive. My . 02

Travis. .

 

[cerberusiam]

I would have to question the ability of the rebuilders to do it 3 times before they maybe got it right. The D70 in these trucks is a pretty stout unit and will stand up with some care. They are a little small for higher HP but in a stock 93 I would look elswhere for the problem. Possibly a bent tube or some thing else not true.



Mine went 270k before the ring and pinion started showing some signs of problems and that was with some synthetic gear oil that trashed a set of bearings. Trans went the same towing in OD and not babied. The first half of its life was in front a 30 ft 5'er, the rest twoing my 4 horse slant and other assorted trailers.



No matter what you change in the drive train it isn't going to affect the rear end rpm's or the stress on it. The trans is going to take the brunt of work when towing no matter if its in or out of OD or thru a aux drive unit. If your concerned an upgrade to D80 from a 2nd gen would be more cost effective.





My 02.

 

[1stgen4evr]

Two speed for one ton.

You are far from stupid. LOTS of folks have dreamed of a two speed for these trucks. Unfortunately, there is no such animal. I beat that horse to death in 1970. Spent a pile of money and got zip. I needed two piles of money to make it happen. The closest you can come to what is need is to use the lightest eaton from an early international two ton. The ratio is way off and to make a gear set would cost, as I mentioned, two piles of money. One of the add on overdrive units that can be either mounted to the transmission or installed 'in line' as part of the drive shaft will get you to the ratio and action of the two speed. It will also give you as many speed as you can possibly need. There are a couple of major players in that market. Neither is bullet proof but they both work well.



On the repeated failure of the rear axle, someone is doggin the heck out of the truck or the rebuild wasn't done properly. You also have the option of going to a Dana 80 which willl take somewhat more load and torque. Your automatic will serve you well but you might want to look into one of the better rebuilds with the various upgrades. From what I see posted here, the aftermarket is really serving our needs quite well on the automatics. A lock up converter with a 3. 73 ratio would cover a wide range of applications quite well. If you are a mechanic, you could piece those things together and save a good bit.



PM with your regular email address and I will go into whatever detail you want as to the attempt at doing a two speed.



James

 

[BHiggins]

cerberusiam,

The original post said he was thinking of changing the axle ratio to 4:11 with a two speed rear, I said he could just change the ratio in the existing Dana to 4:11's and THEN add an overdrive just to regain top end highway speeds. This would in fact change the "rear end RPM's" and "stresses" as you put it.

 

[1stgen4evr]

Od

The GV OD can be installed as OD or UD with the proper connective "tissue".



James

 

[1stgen4evr]

two speed functionality

cerberusiam,

The original post said he was thinking of changing the axle ratio to 4:11 with a two speed rear, I said he could just change the ratio in the existing Dana to 4:11's and THEN add an overdrive just to regain top end highway speeds. This would in fact change the "rear end RPM's" and "stresses" as you put it.

And for now, that is as close as anyone will get to a two speed. I still dream- - - -



James

 

[TKingsbury]

The GV OD can be installed as OD or UD with the proper connective "tissue".



James

Cool, I did not know that. I still don't like the idea that it has to see alot of driveshaft revs before it will work. I like the idea of using something like this from a dead stop. Especially for the kind of money a guy has to lay out for one of these aux units.

Travis. .

 

[AHuggard]

from Orgional poster

Guys, As a less then 1 week member of TDR I am amazed at the weath of knowledge and the willingness to share it. I can see that what ever I might do will be costly and it seems to me from the info you all have provided that I just better just watch my loads nor buy a bigger truck. I may consider a better transmission from one of the after market rebuilders and perhaps the Dana 80 rear end. I will however immediately check the drive shaft alignment and check for a bend. I asked for a 2 speed discussion and I got a good one. Thanks to you all. I am certain I just saved a bunch of money that I really don't have or care to spend.



Al