dgrinnan Posted April 28, 2023 Report Posted April 28, 2023 I think I need to rebuild my rear differential. I had a few questions. First, does anyone know what the gear ratio is in a 47 Dodge WC? Does anyone know if anyone sells a kit to changeout the rear gears to improve the gear ratio for better cruising speed? If no upgrade for the rear is available does anyone know a good source for replacement parts? Quote
Dave72dt Posted April 30, 2023 Report Posted April 30, 2023 No one sells a "kit". You may find some used gear sets with a different ratio. Swap meets, salvage yards, internet. Common upgrade is an axle swap from Jeeps, Rangers, etc.. None are a direct bolt-in swap. I'm guessing the ratio will be stamped on the housing somewhere. Quote
PT81PlymouthPickup Posted April 30, 2023 Report Posted April 30, 2023 Others here might have a more definitive answer on which differential ratios were available when our trucks were first built, but I'm thinking most of the 39-47 Dodge / Plymouth 1/2 ton trucks most likely had 4.1 ratios. When I first rebuilt my truck in the late 1970s I found a low mileage 3.9 ratio pumpkin which I took out of a circa 1950 Mopar car. Other than the ratio, it was the exact same carrier (pumpkin). It worked well with tall tires. Plenty of pull on hills and lower revs on the highway as compared to the 4.1. I ended up taking it out when I installed a T5 transmission because I no longer had an emergency brake on the trans. I installed a 3.55 ratio rear out of a jeep Cherokee. It works OK, but struggles on long hills. If I were to do it over I would select a 3.73 ratio. I think several others on here might agree with 3.73 ratio as being a good choice for our trucks? Anyhow, if you want a perfect bolt in condition complete rear end with a 3.9 ratio it's free to you or anyone else that might want it. Drums and brakes are all like new as well. I won't ship it, but I'd be happy to see someone come get it that might use it. 1 Quote
dgrinnan Posted May 1, 2023 Author Report Posted May 1, 2023 That is a tempting offer. It is a 9 hour drive but doable. Let me bounce it around my head a little bit. Quote
PT81PlymouthPickup Posted May 1, 2023 Report Posted May 1, 2023 3 hours ago, dgrinnan said: That is a tempting offer. It is a 9 hour drive but doable. Let me bounce it around my head a little bit. No rush! It's been sitting in my garage for almost 20 years. Lols! Quote
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