remanufactured Differential Gears



  • allan
    allan Member
    I will commit to 2 sets of the 8 bolt units.
  • Thanks Allan, you're in....and you should be! started this long and winding thread :)
  • Park, thanks for the ditty on a great way to combine OD with a new gearset!!
    7xPacemaker, regarding putting these gears behind a 175:  I can't answer that question so I reached out to a couple of members, including Allan above, who have experience with a number of different drivetrains/use of taller gears, and the general consensus is "not a good idea".  The 175 may not have quite enough power.  They say to approach this combination with caution - not saying that it absolutely wouldn't work.
  • Jon B
    Jon B Administrator
    edited March 2021
    Regarding the possibility of the pinions having changed dimensions when the 6 bolt ring gears changed to the 8 bolt version in 1939:  I checked the parts books, and the 1938 (6-bolt) pinion has a different part number than the 1940.  This suggests that you would have to machine separate shafts for the 6-bolt pinion (1938 and earlier) and the 8-bolt pinion (1939-46).

    Incidentally, the Hudson interchange manual says that the ring gear (at least the standard 4-1/9 ring gear which is a 6-bolt) will fit Terraplanes from 1933-up and Hudsons from 1934-up.  However, looking at the 1933 parts book I find that the 1933 pinion gear (in 4-1/9 ratio) has a different part number from that of the 1934-and-up Hudson products.  Thus, in order to use the reproduction high-speed ring gear in your '33 T, you'd have to custom-machine a  mating pinion, since the repro one would only fit from '34-up.
  • hudsonsplasher1
    hudsonsplasher1 Senior Contributor
    bob ward said:
    Your call, but for me I would go for new bearings. Assuming you are having a pro set up the new gears in your pumpkin, he/she will know where to source them.
    Thanks Bob.

  • Thanks Jon, for the great research on pinions/shafts; and Bob for bringing it up!  That will need to be double-checked before production...also, the good notes on the 33-34 timeframe.  The original and reman parts which are being gathered will answer many questions, but if anyone has any field experience with the pinion/pinion shaft changes, please weigh in, as there is still plenty of time before production.
  • Hans
    Hans Senior Contributor
    Just Musing:   The Pinion gear end should mesh with ring gear,  no problem expected.

    The length and diameter of bearing surfaces supporting pinion shaft require attention.

    Perhaps evaluating inner diameter of bearings  supporting the pinion shaft will provide some comaprative info.

    Over all length extending out from Pinion carrier and sufficent room for companion flange are another item. 

     I just wonder if later pinions have a longer over all length.

    I hope these are thought provoking and helpful.
  • Hans
    Hans Senior Contributor
    Just looking at pinion bearing cone and cup numbers for 1932 ET.

    Pinion front bearing
    Timpkin cone   24112
    Timpkin cup     24262

    Pinion rear bearing 
    Timpkin  cone     3199
    Timpkin   cup      3120



    Pinion-Front & Rear-TIM Cone 3199, Cup 3120-A


    does any one have cone and cup info for 41 and later to compare?
  • bob ward
    bob ward Senior Contributor

    I would love to have 3:55 gears in my '39 112 but am concerned about how hard the 175 would have to grunt to get the car moving from a stop!

    One thought is a try it and see approach, if you don't like the stiffer ratio the new gears will be saleable. Might be best to obtain another pumpkin and fit the new gears to that. Keep your old pumpkin in one piece so you can readily swap it back if need be.
  • 1) Hans, good musing -seems like pinion length/shaft diameter, bearing size, maybe companion flange also, are all areas to doublecheck - as related to the change from 6 to 8 bolt.  We'll have to be sure all necessary parts for both types are in front of the manufacturer.

    2) Bob and 7X, I wonder if someone out there somewhere has been the guinea pig....tried an axle from a different vehicle or the like.  That experience would be helpful to the 175ers.
  • Richard E.
    Richard E. Senior Contributor
    I have been asked as a user of the 3.5:1 gear set in my '36 Terraplane sedan to comment on the performance that I have with its use.  I obtained one of the last sets produced by Pat McDonald (though Ivan Zaremba) sometime around 2005.  I live in Southern CA and one has to get on the frwy to go most places and the original gearing just didn't allow me to drive comfortably at higway speed.  This gear set has allowed me to cruise comfortably at 65 mph.  I have put over 3,000 miles on the car with these gears in it and have no complaints.  This includes roundtrip from my home in Escondido to the HET meet in San Mateo, the All CA meet in San Simeon and the Laughlin Economy Run.  I live up a very steep hill from the I - 15 frwy and yes, I am in 1st gear by the time I get midway up the hill, and occasionally if I encounter a particular steep climb out on the highway I will be poking along in the slow lane.  However the car takes off in 1st gear with plenty of power and I have a very wide range in 2nd.  Finally, if they were available, which they are not, the '40 overdrive might be a better solution, but finding one and rebuilding it would be considerably more costly than installing these gear sets.  So I commend the folks that are seeking to build a new run of these gears and making the eight bolt sets will create a bigger market.
  • Richard, thank you for weighing in....your actual 'field experience' with these gears is valuable information for those of us who are planning to make the gear swap.
  • BigSky
    BigSky Senior Contributor
    I have 3.45 gears in my Ford rear end which is in my 37 Coupe.  I’m running 225/75/15 tires (28.3 inch diameter)  and have had no problem with take off or pulling up hills.  So I would think the 175 engine should do fine if it’s in good health. 
  • Thanks BigSky for another good testimonial on taller gears!

    PROJECT UPDATE:  Great news!!  
    We are at 10 customers for the gear sets, assuming those who have come on board 'stay on board' :) .  It's important for us to remain committed, as it could make or break the project.  Tom Lynch is working with the CNC gear manufacturer to see how close we can stay to the 1300.00 per set mark, if the order ends up being closer to 10 sets versus the original quote for 15 sets.  Once the manufacturer receives all of the 6 and 8 bolt example gears and carriers, he will do some final figuring, and based on how many retooling factors are involved between 6 and 8 bolt gear sets, he may be able to keep the cost at or close to the original quote.  

    I will be contacting all of the 'customers' over the next week for final commitment.  In about 2 weeks, assuming all is still a go,  the next step will be arranging to collect the deposits (1000.00).  The manufacturer will set up an escrow account, taking the burden off of any of us club members,  Per Tom, if and when the 'final deal is made', we customers will then be placed in direct communication with the manufacturer....and ultimately the new gears will be shipped directly from the manufacturer to us.  

    There is still time....any more takers?  I, for one, can't wait to install my new gears.  Tom feels the same, and when we were talking today, he said "it will be nice to keep up with traffic without worrying about throwing a rod".   :smile:

    Questions, please ask!  Suggestions, please suggest!  Thank you!
  • At other club members suggestion, I talked with Paul Schuster (club member, Pittsburgh, PA area) about this project.  As many of you know he is an expert machinist, not to mention restorer of Hudsons.  He echoed the pointers and concerns that Bob, Geoff and others on this forum have brought up:  that, especially with the 6 bolt set up, the original tab-type lock washers MUST NOT be re-used.  Instead, use modern hardened replacements for both lock washers and bolts.  He also reiterated that the housings will have to be be ground out in certain spots to fit the new assemblies in  (Bob W. also has some information and photos on where to grind earlier in this forum thread).  Paul has dissembled, repaired, and properly setup Hudson differentials for many other club members, and I asked him if his services will be available for any of us who will be purchasing gearsets - and he said 'yes'.  The newer club members may not know him, so I will say that he comes highly recommended.  He also has all the necessary hardware and bearings.  I'm not his agent :) , but I wanted to get the information on this resource out there.
  • The order commitments came rolling in yesterday and today, so unless there is some unexpected hitch, it looks like this project is a go!  Are there any other takers?  Speak now, as there may not be another opportunity to get these gear sets for a number of years, at least at this group price.  
    In regard to Paul Schuster, the expert mentioned in the previous post: it did occur to me that since these new gears will be coming in all at once, and since Paul has a lot of other projects at any given time, he may not be able to meet all of our needs.  If Paul can't help all of us within our project timeframe, there are certainly other folks in and out of the club who will be able to help....unless you are a do-it-yourselfer, then you don't have to worry :) !
  • ajet
    ajet Member
    Nice to see a group get together and solve a problem. 45 mph doesn't quite  "do it" today !
    If you've got "room" add me for 1 8bolt set.
    Sent you an email.
     Thanks ... Bill
  • Thank you Bill!'ve been added to the the confirmed list.....
  • hudsonsplasher1
    hudsonsplasher1 Senior Contributor
    I have a set of gears that Ivan had made and I picked them up at the Colorado meet. Just talked with the company that putting the gears in and they said the ring gear won't fit because of different matting surfaces. Anyone else have a problem with this? Any help much appreciated.
  • Ric West IN
    Ric West IN Senior Contributor
    Page 2 of this thread/discussion has picture of the modifications needed to fit Ivan's ring gear.  
  • bob ward
    bob ward Senior Contributor
    edited March 2021
    hudsonsplasher, I've had a set of Ivan's gears made up into the pumpkin by a pro and I fitted the pumpkin to the axle myself. 

    The pro's work went without incident. He took extra time because as he said "I have to be careful I don't miss something that 80 years and many pairs of hands have wrought"

    My work, fitting the pumpkin to the axle went without problem. Altering the notches in the diff housing to cater for the different shape ring gear is a 5 or 10 minute job.

    This is a fairly well worn path. Did your diff company say if they are having problems building the pumpkin or fitting the pumpkin?

  • Gene, it will be important for you (and all of us) to get to the bottom of the particular issue you are experiencing, as a new batch of gear sets will be "coming off the presses" later this year..... and we are focused on getting the repros right in all respects, which entails gathering all of the original 6 and 8 bolt parts to be used as models. 
    Others with more expertise will hopefully weigh in here, but I'm wondering what exactly your rebuilder means by 'mating surface' differences?  Is it the necessity of a housing modification/grinding in order to get the parts into place; a carrier/crown gear alignment issue; a pinion/crown gear mating issue, or something else?
  • Gene, or is it a possibility that, unbeknownst to you, your car had an 8 bolt carrier  (the Zaremba sets are for 6 bolt carriers).
  • Jon B
    Jon B Administrator
    One pertinent question might be: Whose reproduction gears, exactly, are being used as the prototypes for this latest reproduction project?  Weren't several versions made over the years?  The "factory" set, Pat McDonald's repro's, Ivan Zaremba's, and maybe even Gus Souza's?  You'd want to be sure that you use a tried-and-true gearset as your basis for production, based upon people's experiences after installing that particular set in their car.  But, are those who say "so-and-so's repro gears worked perfectly in my car" absolutely sure of whose gears they actually had installed? 
  • Jon, agreed.  Tom is in the process of gathering factory original parts (6 and 8 bolt crown/pinion gears and carriers), which will be provided to the manufacturer.  In addition to this, he has an Ivan Zaremba 6-bolt set, which will also be loaned to the manufacturer for comparison.  Note that this could have already been done, but it was decided not to be shipping gears until we knew there were enough customers.......BTW, to keep the cost down, we could still use a few more of you to hop on the train.....not begging, just promoting group benefit and making sure no one gets left out.  It's not too late...we are in the 'soft close' phase, like some auctions  :) .  I know it's a hit in the pocketbook, but the way I'm looking at it is like an insurance premium....I rebuilt my splasher once and I want to help insure that I won't have to prematurely rebuild it again!  More driving, less revs.... 
  • Jon B
    Jon B Administrator
    That's good.  You've obviously given careful thought to the repro process, and have several examples of gears for the manufacturer to study.  By the way, have you sent in something to the WTN about your project?  I realize that the next issue is away down the line, but even so, the article might produce a flurry of sales when it finally appears.
  • Glowplug
    Glowplug Expert Adviser
    The project was sent to each of the chapters for sharing.   Some did email out and others put in their newsletters already.
  • Jon, with your and others' help and suggestions, as Glowplug says, the word has already reached a large swath of HET'ers.  But, to answer your question about the May-June WTN, I first had to talk with Tom, who has discussed the longterm with the manufacturer, and the answer is YES, we will put something in the WTN about this project. 
    Here's the plan:  the current project, which includes all of us who have made firm commitments, will move ahead as planned.  To get in on this first run, we would like to hear from interested parties by the end of March.    The main reasons for this deadline is to respect those who have stepped up and committed to this project....and to stay with the original goal of not dragging things on too long.  
    HOWEVER, because the manufacturer will already have the computer programming done (and this is a major part of the project), there will be an opportunity for future customers to purchase sets.  What we don't know for sure is the cost per set after this first run....that will up to the manufacturer, but it will not be like starting from scratch. 

    Any questions/suggestions, please speak up.  We are trying to keep everyone up to speed as much as possible.  Jon, if you, or anyone else, has any suggestions as to how to present this in the WTN, please let us ad or a short article or....?
  • Glowplug
    Glowplug Expert Adviser
    edited March 2021
    Put together the pitch for these gears.  Who what why when and how questions answered.  Present the pictures of what you are pitching. The team doing the leg work, the design and manufacturers.  Timelines and cost.  There are lots of folks who know zip about exchanging the gear sets... but if a path to purchase install and enjoy without hassle is laid out those folks may be your best customers? Put together a page in MS Word or MS publisher with your pictures to show what you words are explaining.  Make sure the pictures are publication ready meaning high definition JPG.  Richard Low or Sam Jackson ( contact info in WTN) can explain details.  Good luck March 30 2021 is deadline for next WTN
  • Glowplug, Thanks for the ideas!  I will contact Sam to give him a heads-up/ask questions.  Bob, you had posted some pictures - do you have any showing the carrier and gears?  Or anyone else have any?  Weigh in here or send me a PM, as I agree that pictures would make it more interesting.