Al Peterson Posted July 17, 2018 Report Share Posted July 17, 2018 I've searched a few threads on here from the archives and didn't really find anything helpful but I wanted to ask again because it's been quite a few years since someone has asked about ring and pinion sets. I currently have a 1947 WC truck(3sp) with a 4.1F rearend set and would like to go to a stock 3.73. How common are they? Can you get aftermarket? If so, where(I haven't found any yet)? I'd like to keep this truck as stock as possible. My goal here is to be able to take longer trips with the truck and not have to worry about highway speeds(55mph) and also not be revving the engine by doing that speed. I recently bought this truck but really don't know much about it yet, I think the rearend is a 8.25 ring gear size, is that correct? Thank you for any help! Quote Link to comment Share on other sites More sharing options...
MBF Posted July 21, 2018 Report Share Posted July 21, 2018 Hi Al. Not sure if this will be of any help, but maybe they've got an old guy there that can get you steered in the right direction. Good luck. http://www.nationaldrivetrain.com/partinfo.php?partid=NDT:MEASUREKIT&choice= Quote Link to comment Share on other sites More sharing options...
Veemoney Posted July 21, 2018 Report Share Posted July 21, 2018 There is a dodge forum on yahoo for the 39-47 trucks that have some good technical info on this. The attached article is one I had pulled previously for myself _Converting Axels to High Speed.doc 1 Quote Link to comment Share on other sites More sharing options...
Desotodav Posted July 21, 2018 Report Share Posted July 21, 2018 (edited) I arranged a Ford 2.92 diff for a friend of mine to install in his 46 Dodge truck a while back and got a message back from him after it was installed saying that he was now expecting to get speeding tickets from his highway driving ? I have completed 2 diff conversions from 4.1 to 3.54 in recent times for my 52 and 53 half ton trucks. I found the process cheap, and also beneficial for highway driving. I am in the process now of installing a bolt-on adaptor between the speedo cable and gearbox which will correct my speedo reading for the 10mph gain (the correction ratio was 1.15). A few thigs to keep in mind if you are considering installing a car diff centre: I found that the car axles were about 1 and 1/2 inches shorter than the truck axles on either side.... the yoke for the car diffs was different but there is no issue with changing your truck one over to the car diff... the axle count on my trucks have been either 10 or 15 spline, and the car diffs which I have used have both been 15 spline. I think that the diff centre change is a well worthwhile exercise as it comfortably allows me to cruise the highways at 60mph now. I understand where you are coming from Al in wanting to keep your truck original, so you will be pleased to know that the change is not visible (apart maybe from the diff ratio number and possibly the casting number stamped on the diff centre). I have not seen a 3.73 diff here in Oz, but the car diff centres that I have worked with have been stamped 4.1, 3.9, and 3.54 (or as a fraction of 3.9 over 11). I wish you well with your venture. Great article too VEEMONEY ? Edited July 21, 2018 by Desotodav 1 Quote Link to comment Share on other sites More sharing options...
Al Peterson Posted July 22, 2018 Author Report Share Posted July 22, 2018 I'm glad I finally got some responses to my post! Thank you, I now have some solid information to work with. 1 Quote Link to comment Share on other sites More sharing options...
DJ194950 Posted July 22, 2018 Report Share Posted July 22, 2018 Buy a classic edition of Hollander interchange book 1946-1956. Like this cheapest I found with a quick EBay search. https://www.ebay.com/itm/1946-1956-Hollander-US-Parts-Interchange-Manual/263797721398?epid=22006523244&hash=item3d6b91c936%3Ag%3AeKsAAOSwnwVanwm1&_sacat=0&_nkw=hollander+classic+interchange+1949-1956&_from=R40&rt=nc&_trksid=m570.l1313 There are many car-mopar third member that with fit in your trucks rear axle housing, but it gets very confusing as to which work easily and it is to complicated just for me to post it here. Buy the book and if you have problems uderstanding how to check the info PM me with your phone and I will walk the pages with you! ? DJ 1 Quote Link to comment Share on other sites More sharing options...
Veemoney Posted May 23, 2021 Report Share Posted May 23, 2021 On 7/22/2018 at 11:53 AM, Al Peterson said: I'm glad I finally got some responses to my post! Thank you, I now have some solid information to work with. Any updates on your progress? Quote Link to comment Share on other sites More sharing options...
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