89' D250 Differential ratios?

Redtruck-VA · Nov 6, 2014

Had the old ******* the rack today and thought I'd check the gear ratio. I expected something like 3:55. What I got has me totally confused. First it's a open rear end. I put a chalk mark on the driveshaft and one on a tire. Asked a friend to turn the wheel one full turn and I got 1-1/2 turns on the drive shaft. No way can that be right.... So what's up???

dodge dude94 · Nov 6, 2014

That's....odd.

There should be a tag on the cover. That will have the ratio on it.

Dodge rear ends were only available in 3.21(ish), 3.55(ish), 3.92 and 4.10.

crazzywolfie · Nov 6, 2014

might have 3.07 gears since it is a older diesel with the 727 trans. getting a build sheet should answer this question

dodge dude94 · Nov 6, 2014

+1 for a build sheet.

Redtruck-VA · Nov 6, 2014

That's exactly what I said...That's odd..

Both rear wheels off the ground. One wheel locked with a wedge. Drive shaft marked with chalk as was the wheel. One full turn of the wheel gave 1-1/2 turns of the drive shaft. 89' 3spd automatic. I have done this in the past with other vehicles and never gotten 1-1/2 turns. I will say my truck does not accelerate with any great speed, but this can't be right...

crazzywolfie · Nov 6, 2014

from what i have read it sounds like you have 3.07 gears. i was reading your suppose to spin the tire 2 rotations and it give you a close idea to what gear ratio you have.

Redtruck-VA · Nov 6, 2014

I agree the truck has a TALL gear, as for turning the wheel, I should have tried the other wheel to see what it did...

Redtruck-VA · Jan 4, 2015

To close this thread, it is indeed a 3:07 Dana 71. It was full of brown soup. So it not only sat for a long time but had water in it. It should be rebuilt with new gears, but after cleaning it and refilling with Lucas gear lube it is about 80% quieter. I'm going to run it until gets noisier... lol
Look pretty ugly inside..

NYCruiser · Jan 4, 2015

May be time to put the gears you want in it

Redtruck-VA · Jan 4, 2015

NYCruiser said:
May be time to put the gears you want in it

Most definitely, being a 3:07 (Dana 71) It would be easiest to change axles for a Dana 70 possibly already with a 3:54 and a limited slip. I got my other truck I need to get back on the road before totally focusing on the 89'.

Thanks,

crazzywolfie · Jan 4, 2015

i think you should leave the gears. 3.07 are probably the best gears you can have for a fairly stock 2wd diesel. switching to 3.54 gears could bring you top speed down by about 10mph.

Redtruck-VA · Jan 4, 2015

I'll have to see what rpm I'm at while cruising at highway speed before knowing if I can live with a deeper gear.

gen 1 forever · Jun 7, 2015

Speaking about a limited slip rear ends, I have a 1992 D250 Cummins and only one tire seems to be spinning. The other does nothing. Can I change out this rear end for a limited slip or am I wrong?

crazzywolfie · Jun 7, 2015

you can do whatever you would like but in the end it comes down to money. LSD are usually not cheap to buy and usually even more expensive to install.

89' D250 Differential ratios?

Redtruck-VA

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dodge dude94

Millennial Boomer

crazzywolfie

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dodge dude94

Millennial Boomer

Redtruck-VA

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crazzywolfie

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Redtruck-VA

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Redtruck-VA

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NYCruiser

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Redtruck-VA

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crazzywolfie

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Redtruck-VA

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gen 1 forever

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crazzywolfie

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