Car side Truck side

[HanksB3B]

I'd like to swap-out my pumpkin from my stock 411 rear and install (is it a "taller" ratio?) a rear end that will give me a higher top speed. I'm sure a few of you know what was available as far as ratios are concerned and from what year and model cars they were available on. What are my options? Any documentation or advice would be greatly appreciated.

Thanks,

Hank

[Young Ed]

Look for a 3.73. 3.54s were made but I've never seen one in person. The newer car you look at the more likely to be a lower(numerically) ratio. After 52 they changed the side gear/axle spline count so if you get one after that you have to swap the side gears out.

[HanksB3B]

So a 3.73 is what I want. Is this from a truck or passenger car what year or model should I be looking for? Are they identical for Dodge Plymoth Chrysler and Desoto? A model number of the autos would help? Are there numbers I can look for on the differential housing as well?

Thanks,

Hank

[Reg Evans]

Hank,

I have this set of NOS ring and pinion gears available for purchase. The ratio is 3.54 to 1. I had another set just like these swapped into my 49 Dodge Coronet that came from the factory with 4.11 to 1.

Before I found these sets of ring and pinions I wanted to be able to go faster with my 52 1/2 to so I looked locally for a better ratio and found that a complete rear end would work in my truck with some modifications of the spring perches and drive shaft. My truck now has a 66 T Bird rear end with 3.0 to 1 ration in it.

[Young Ed]

They were optional in the pickups but I would think quite rare. You're better off looking for a car one. Now someone was saying they aren't built as heavy duty as the car ones but are you hauling 2tons of hay with it? Unlikely. Oh I should also point out this swap works for 1/2 tons and I think 3/4 tons. Anything bigger is likely different. I believe you are right they fit across the lines and would fit 39-54 with the exception of the splines as I mentioned before. The ratio is typically stamped into the very top of the pumpkin which makes it hard to identify them while in the car.

[HanksB3B]

Hank

How easy a project was swapping to the T-bird differential?

Hnak

Edited March 1, 2010 by HanksB3B

[41/53dodges]

anybody know about what to do to make the speedo right?

[Young Ed]

You either have to track down the appropriate tooth speedometer gear for the transmission or get an adaptor which goes between the trans and the cable and alters the gearing.

[Reg Evans]

Some speedo shops can make a little gear box that connects to the transmission end of the speedo cable and corrects your speedometer reading. You have to tell them what your speedo reading is compared to how fast you are really going. A hand held GPS works great for the accurate reading.

[41/53dodges]

im pretty sure the gearbox would be expensive to have made, so does anybody have experience with changing out the gears and what fits in to make it right?

[Reg Evans]

The one I had made was $50.