Has anyone replaced the gears on their Terraplane with the 3:54's ?

dlamb67

I know we have another thread on this but I wanted to hear from anyone who has actually  done the swap. The reproduction gear sets are $1300 and a replacement axle is based on what it will take to fit one,modifications etc. I was wondering about things like changing out the speedometer gear. You want the speedo to be accurate. When I was a kid I swapped a tranny in an old Chevy truck from a three on the tree to a four speed. Could never get the speedometer accurate due to the reducer no clearing the shifter. Don't want to run into that issue. Any other pitfalls . I'm happy with 50 mph,however in todays world your are almost a hazard at that speed. 

Jon B

I haven't done the swap, but I'll pass along one tidbit:  I spoke to one Hudson mechanic who could find no way to get the new ring gear into the housing, so gave up.  Later I spoke to someone familiar with the swap, and he said that one must grind a small notch in the circular opening (in the housing) so that the ring gear can be turned perpendicular to the plane of the opening, and the edge inserted through the widened portion of the opening.  (Widened, that is, by virtue of having created a notch in the opening.) 

As to the gearing problem, there will be no existing Hudson speedo gear made especially to mate with that rearend gear, I fear*.  You may have to purchase a speedometer adapter or reducer.

*-- I have been told that Hudson never produced the 3-5/9 gearset for sale in the late 1930's.  They did list it in their parts catalog but whenever someone ordered one from the factory, it was always mysteriously "out of stock".  The reason: the cars that that the AAA tested on the Bonneville Salt Flats had specially-machined 3-5/9 rearends which permitted the cars to travel at high speeds without having the engines blow up.  These rearends were not "stock", they were machined by Hudson for the occasion only.  But the AAA required that all cars under its testing supervision be made using stock components.  That's why Hudson listed the 3-5/9 rearends in their parts book, even though they weren't available.  Once listed in the parts books, the 3-5/9 rearend gears were officially "stock"!  (I've HEARD this but can't verify the story!  Anyone know for sure?)

jjbubaboy

Hey dlamb67,
My speedo seems to be just about on the money withe the 3.55's in my Mustang rear.
Using stock 16 in rims and radials. I will have to check the size of the tires as this is what helps with overall height which effects the amount of rotation and has seemed to correct for the gear change.
Jeff 

bob ward

I have an axle with the new 3.54 gears waiting to go in our 35 H8 roadster project when it comes back from the panel beater. I probably won't fuss too much about speedo gears I'll use something like this instead.
http://www.ebay.com/itm/US-Universal-Car-GPS-Speedometer-HUD-Head-Up-Display-MPH-KM-h-Overspeed-Alarm-/361735721845

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allan

To Jon's comment about the mysterious gears - I have acquired a very worn one a number of years ago. The one I got was only the second one I ever ran across. However Headley told me they were more common in the western flat states. I'm going to see if the one I have can be saved and install in the '41 8cyl I am going to work on next. The ratio is too tall for my splashers to handle. Allan