Diff. questions

[BHerring]

Hey all,



I am thinking about putting in a limited slip diff, how can I tell what ratio I have currently installed.



I was thinking about putting a lower gear to help with gas mileage. . any comments on this.





I have a 1993 D250 w/auto, std cab, 2 wheel drive.



Any comments will be greatly appreciated



TIA

 

[dpuckett]

When you say lower ratio to help with fuel economy, you numerically lower, right? That is traditionally a higher gear, as it allows a higher top speed, all else being equal.



Jack up your truck's rear axle. Spin a wheel. If the opposite wheel turns the other way, you have an open diff. If it just sticks there, you have a posi. Turn each wheel one full turn, and keep an eye on the pinion yoke. If it turns a little more than 4 turns, you have 4. 10 gears. If 3. 5 turns, you have 3. 54s. If something between the 2, you have 3. 73s.



FYI (and for anyone else who may or may not know) You dont need to change ratios when installing a limited slip carrier.



Daniel

 

[BHerring]

dpuckett,



Thanks for the info, I know for a fact its a open diff.



Going to get a posi / limited slip...



Next is the ratio, need for fuel economy,



So would I want a 3. 5 or lower or would it be the 4. 10, I always get confused on the gears, and yes the lower the number is better fuel mileage right... .



Also what company would you recommend to purchase a new diff.



Thanks

Brad

 

["Mad Max"]

i'd highly recommend 3. 54's for the best overall mileage. My '93 rig gets 20 mpg, and that's generally regarded as the 'typical' mileage. I also am running a 35" tire - no sweat. I'm actually putting 38s on my other Cummins-powered rig and it also has 3. 54's - I'm looking forward to it's performance as well.

- M2

 

[BHerring]

UPDATE...



I jacked up the ole dodge and rotated the tire ONE full turn and the yoke/drive shaft rotated 1 3/4 turns... .



Here is the tag info on the diff



1st Line: 52068056

2nd Line: 3 54 605509-7





What does all the numbers mean?? and what ratio is my diff. .



Thanks in Advance



BH

 

[dodgenstein]

3 54 is the ratio. 605509 is the bill of materials number (BOM). A dealer with access to Dana/Spicer BOM info can tell you anything you need to know about your axle.

 

[dodgenstein]

Found this:Axle Bill of Material it liststhe axle as a std. (open) 3. 54 in a 91-93. 5 Dodge application and gives the Dana part numbers for the internal parts.

 

[BHerring]

Hello all,





I have removed my ABS. I am going to get a limitied slip gears. Would like to know if anybody has installed a 3 23 or 3 07 gears.



I currently get approx 18 MPG, and would like better MPG, I dont pull or haul anything.



Any and all comments will be greatly appreciated.



Brad

 

[PToombs]

Brad, are you getting a new or used LSD? I am thinking about going the same direction, as lockers don't really sound feasable for my use. I plan on keeping the same ratio.

Thanks.

 

[BHerring]

PToombs,



I will most likely go with a new one because my thinking is I dont know have any ideas on what adventures the used LSD has been on. .



I have never worked on Diesels, so I have no idea if the 3. 07 is going low for the ole truck because of the RPM's at take off, however I will gain more top-end speed, just will slow taking off, so I might end up with 3. 23. I have a spread sheet of my gears, transmission gears, and my best bet would be the 3. 07 espically in the long run.



The next question is who makes a good gears for our trucks, I have used Auburn gears on my sport cars but I dont know if they support Dodge and plus I removed the ABS crap, so I dont have to have that "special diff"





Brad

 

["Mad Max"]

Fellas, as far as what brand of gears to use, I would recommend the strongest ones available and those are most likely the rear Dana gears. The quality will matter because of the torque, as will the competency of the guy doing the install.



On the LSD, I like the LSDs over lockers, and a good factory LSD replacement - I think they were call a 'Tru-Trak'?? - would be my recommendation. Even in our 6BT-powered Ramcharger with 38s I'm using the factory LSD. Not much trail time on it but so far it has performed perfectly, and on the street, well, it's perfect there too.



IME, off-road the front lockers are more important than a rear locker, and I have an Eaton E-locker in the front 60 and the LSD in the back. IMO best of both for an off-roading street truck.



- M2