Help with 1937-40 rear axle rebuild

C

Chester Leighton

Junior Member
I'm getting ready to overhaul the rear axle in the 37 Pickup I got from my father. A little background on this. He had a 5 speed T-5 transmission put in it and an open driveshaft conversion before I got it. The truck had been converted to 1940 hydraulic drum brakes and a 1953 8BA engine installed before he got the truck. All that said, it still has a 4.44:1 rear end ratio. I don't know if the rear axle is 1937 or 1940 or if that even matters. I'm looking to put a set of 3.55 gears in the rear axle, replace the carrier bearings, thrust bearing, pinion bearing and outer axle seals. I've overhauled a model T rear end so I'm familiar with having to shim the axle housings to set the carrier bearing clearance and pinion gear lash. What I don't know is how do you know when you have the correct carrier bearing clearance? How do you know when you have the correct preload on the thrust bearing? Is there a book or some other info I can get that walks me through this? I've watched some U-Tube videos and they were helpful but didn't give me the detail I'm looking for. I also have a motors manual that I've read but again, doesn't go to the detail I need. Or, is there some where reputable near Lynchburg Va. that does this work?
 
If you are familiar with the gaskets setting the lash on the ring gear and pinion, you should be able to do this. The 4.44 is from a V8-60. You will be quite happy with 3.55. I have a KRW pinion bearing setting tool. After setting a new pinion with it, I checked it with a calibrated inch-pound torque wrench and it was 30 inch pounds turning the shaft from the torque tube end. Keep in mind used gears are a bit trickier to set up. Go for new.
Good luck.
 
Keep in mind used gears are a bit trickier to set up..[/QUOTE said:
Interesting..... My preference has always been original, old, used, absolutely Ford script. 'Select' used, meeting my visual criteria. Just opinion.
Click to expand...
 
the way I set the pinion preload [learnt this trick here on the 'barn] is to assemble the pinion/bearing setup in the banjo. Hold the spline of the pinion upright in a vise [so the banjo is facing up]...spin the banjo as hard and fast as you can...it should only rotate between 1/2-3/4 of a complete turn when preload is set correctly.
 
The 3.54 gears with a 10 spline pinion are a bit difficult to find in good used condition, and nos is nearly impossible. Good used 6 spline sets are much easier to locate.
I would suggest doing a search in the archives here and on the H.A.M.B. - Jalopy Journal for threads on this subject. Some of these threads should lead you to full written procedures.
I've rebuilt a few of these rear axles ('35 - '40) for my own cars and some for my friends. It's not really that difficult of a job, but take your time, ask questions here, and get it set up correctly on the first try.
 
Good advise from John above ^^^ I only suggest you use google for the search. Seems to work better for me, Just do the search with " fordbarn" or " Hamb" included in the search. Example, I would try "differential preload fordbarn". Or similar . Brians method is what I shoot for when I do mine.
 
Here is one that sold on eBay for $73.00. Its missing its calibration spring so it's useless. Both KR Wilson and Manzel made them. I've only seen one of the Manzel's for sale and it looked like a nicer tool than the KRW. I have a KRW one but I'm too lazy to go out and dig it out and take a photo of it. If you were to get one of those pinion spine adaptors and then weld a quarter inch socket to it then you could use a modern inch-pound torque wrench to set the pre-load. Somewhere in my factory literature I saw the pinion pre-load specs but I don't remember what they were. The early factory instructions said to set the preload with the assembly in your hand, with a rag around the bearing race and then tighten the pre-load until the pinion bearing starts to spin in the rag instead of the bearing. Then they heated the housing and dropped the pinion assembly into center-section. That doesn't seem very scientific, I would prefer the preload tool with the inch-pound specs.

I've rebuilt rearends, maybe 200 or more at the phone company over 30-years but I have yet to do an early Ford. One of the things the old-timers taught me on the first one I did when setting the pinion preload was to get it set where it needed to be and then smack both sides of the pinion with a punch and big hammer. The bearing pre-load would loosen up. Then they would adjust it back to the pre-load spec and then smack it again. It would loosen up again. After a few smacks and minor adjustments, the pre-load would not change. We did this whether they used shims or crush sleeves. I would think with the races driven in until they bottomed out and bearings pressed on, they shouldn't have loosened with the hammer smacks, but they did.
 

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The above K R Wilson tool is missing it's special spring Do Not Purchase, beside there is no need for it. An inch/# torque wrench with a pointer is good. You can find Spec. and instructions in Ford Service Bulletins. T
 
Hi
I change mine with help of VanPelt book , old gears was 4.44 now 3.54, i am happy and my flattie are too
 
The KRW preload tool is one that in my opinion, was never used by experienced mechanics back in the day. When I used it on my banjo, the indicator mark was acting so erratically that I couldn’t tell where it was set at all. I gave up, and took it to an old timer who set it upright in a bench vise and with both hands, gave it a whirl. By dumb luck, I had set it correctly myself, as with multiple spins, it would barely or almost make one complete revolution.
My gear set is a 3.78, which replaced a 4.44, which would have been a good set for parades, but I wanted a highway set. I’ve toured through 19 states and a bit of Canada with that gearset, which to me, proves the KRW gauge to be excess baggage.
In reading through the KRW catalogues, I believe that they went overboard on designing and producing a number of tools that saw little use at all.
 
Thank you for the responses. That covers the the input shaft thrust bearing pre load. How about the carrier bearing preload? How do I know when I have the housings shimmed correctly?
 
Also, I currently have a 6 spline input shaft. I have been looking at the Speedway catalog and they have new 3:55 ring and pinion gear sets that they advertise to fit this rear axle. I was also going to purchase new carrier bearings and the pinion and thrust bearings for the input shaft. I would think they have those as well?
 
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