During the summer I took apart my rear axle and the project stalled.
One of my challenges was it was hard to get started without having parts I needed and I couldn't get the parts I needed unless I first checked everything...
The MTFCA axle book is helpful, but you have to read/follow the whole procedure to check the parts then restart when you have everything.
Here is my attempt to make a checklist:
Rebuilding Model T Rearend.pdf (53.7 k)
Here is what is in the PDF. It looks nicer in the PDF, but I know some may not be able to open it.
Rebuilding Model T Rear-End Checklist
The Drive Shaft Assembly
1. (5171) universal joint: [ ](2574)pin(always replace) [ ]rivets tight [ ]wear ok (0.010-0.020”)
2. (2595B) drive shaft: [ ]surface (0.095-1.000”) [ ]under sleeve surface(1.000”) [ ]threads ok
3. (2589) thrust bearing assembly: (2591) steelracesx2 [ ]ok, (2591B) bearing [ ]ok
4. (2596) inner bearing sleeve [ ]ok (1.248-1.250”), (2598B)woodruff key [ ]ok , (2598)nut [ ]ok
5. (2587) pinion bearing [ ]ok (0.560-0.562)
6. (2583/B) drive shaft spool [ ]ok (2.372-2.375), [ ]fit in assembly ok
7. (2581) drive shaft bushing [ ]brass and ok(.002-.003 side-to-side play, 0.002-.005 end play1)
8. (2597B/2518) ring gear and pinion [ ]pinion ok, [ ]ring gear ok
The Differential Assembly
1. (2501/2) right/left axle housing [ ]ok, [ ]sleeve ok (2.210”), [ ] pin ok, [ ]housing alignment ok (see page 27)
2. (2511) inner seals [ ]ok
3. (2505) axles [ ]bearing surface ok (1.060-1.062”), [ ]gear shoulder diameter ok (1.806-1.807”)
4. (2508) roller bearings [ ] ok( 0.4800-0.500”)
5. (2509/09B) axle bearing sleeves [ ] ok
6. (2524/26) differential gears and spider [ ]spider gear arm play ok (0.005-0.007”)
7. (2528/2529) thrust washer assembly (2529) [ ]steel thrust washer ok (0.090”), (2528) [ ]bronze & ok
8. (2512C) left differential housing [ ]axle bearing clearance ok (0.005-.0010”), (2531B) thrust washer pin ok [ ]
9. (2513C) right differential housing [ ] axle bearing clearance ok (0.005-.0010”), (2531B) thrust washer pin ok [ ]
(2506) axle shaft washer (two may be needed)
Matthew, I hope you don't mind. I made a copy of your list. I pulled the rearend out of my '26 sedan today and your list is fairly comprehensive with some good notes. Thank you. Keep us in touch with how things are going.
I posted the list hoping that it would help others. Also I hope people can give there input to help me too
We will have to compare notes as we fix our rearends ;?
Here it is on a jpg:
A close-by friend that has worked on one before?
Matt, I am also redoing the rear axle of my 1926 TuDor. Here are a couple of pictures of items that could be added to your list.
Check the Axle Housing halves to be straight
Check the Axle Housing halves for cracks
I found my housing halves to be straight.
With the axle housing on a flat surface and using a couple of squares I checked the axle tube to be straight. Mine were within 1/32".
But....... I found a couple significant cracks in the outer sleeve area.
I like your check list and will add it to my stuff. I also include a small picture and list of the clearances and sizes of axles, shafts bearings etc.
Anyway, maybe you should check your housings before you get too far. I going to replace mine.
Mike, is it a true crack or a bad gouge from primitive sleeve install/extract methods?
There are gouges that you can see, but these are cracks. I honed the tube and the gouges go away, but the cracks do not.
I was hoping
The only thing that stands out to me is the driveshaft diameter. You state that the diameter is .995-1.000. If that's the case I think you might have excessive clearance on the bushing. Remember the square end where the ujoint rides will have no wear so the bushing must be a couple thou larger than 1.000 for the end to pass thru. So if you have a .995 diameter in one part of your drive shaft, you may have excessive clearance. Something to check again.
Also your steel thrust washers are pretty thin, most are about 5 thou wider. Its not really important since you will be adding shims to set the ring and pinion and the side to side clearance of the diff housings will be controlled by the thickness of the bronze washers, which can be machined. Just something to note.
As a matter of course, I would recommend replacing all gaskets and seals and using modern seals. I would also recommend replacing any roller bearings with loose cages. Use 600 wt oil, available from the vendors, and don't overfill (1.5 inches down from hole). While you have it apart, consider installing a pipe plug in the bottom to make draining the differential case easier. Put the differential together with only the left tube first to check the gears for proper engagement. Use some grease to see the pattern.
You should check the drive shaft to make sure it is straight and balanced.
Also, chuck the left diffy case into a lathe and make sure the mounting surface for the ring gear has zero run-out, you'll appreciate this later when setting up the ring and pinion backlash
Other than this, your list looks relatively complete
Save the cracked housings for people like me that would try welding them.
Matthew, Richard has a point re the wear at the front bush. If the shaft is worn there will be excess clearance, even if you replace the front bush, because the square end of the shaft must first pass through the bush.
This is easily overcome. It takes a light skim with an angle grinder to remove the merest amount of metal from the points of the squares on the driveshaft. Measure what you take off with calipers until you are just a tad under the diameter of the worn journal. Then you are set to ream a new bushing to suit the shaft.
Hope this helps.
Allan from down under.
Thanks for everyone’s input!
First off, I want to say that this is intended to be used with the MTFCA rear axle guidebook. The reason I think that this helps is that it helps me know every part I should check and order before assembly. If you follow the guidebook step-by-step you may get almost done before you find you are in the marked for a new axle ¾ of the way through… In that case everything you order may not bee needed…
Wayne, I havn’t found anyone in my area, but I agree that would be the best help.
Mike, I changed step 1 from housing “alignment ok” to “housing strait” (as far as cracks I just have an “ok” to check. My hope is that everyone would inspect parts carefully. Can you explain how you check yours is strait. It looks different than the method in the guidebook. You mention: “I also include a small picture and list of the clearances and sizes of axles, shafts bearings etc.” I did include pictures and some clearances. What sizes would you add?
Richard, please understand I am not an authority on this. This will be my first axle to rebuild. All I did was take date from the MTFCA guidebook. On page 17 bottom left it states: “…surface for the (2581 bushing should be 1.000 inch. If you have a used drive shaft, wear on this bearing surface up to 0.005 inch is acceptable…” As far as thickness of steel thrust washers again I used guidebook. I will add a “greater than” symbol. This is just to maker sure some reason they didn’t get way to much wear…
Neal, great idea to add gaskets, modern seals, and oil I added them to the list. As far as oil plug that is a great idea, but I think I will leave it off because I want this to check for replacement parts… I will also added to step 8 to check proper engagement, but imagine that most times new parts will have to be ordered before getting to this step.
Andy, I added strait to the drive shaft. What do you mean by balanced? I also added the bit about making sure ring gear surface has zero run-out
Kep, we have to save everything for you. I love your profile pics. Almost look like my car. Actually the running chassis that I have is good, just the body is a bucket of rust ;)
Allan, I agree with you and Richard. The MTFCA manual covers the issue, just as you stated.
I have a question for everyone. In inspecting roller bearings besides the cages tight, no pitting and clearance of bearings… Is there anything else to check. Like the overall length? Or wear on ends.
Here it is with updates:
and the pdf:
Rebuilding Model T Rearend.pdf (55.8 k)
My method for checking for a straight axle is not as accurate as others that have been mentioned on the forum. My method is to place the housing half on a flat surface. I use my cast iron table saw top. Others have a piece of thick steel that has been machined flat. I always check the housing to see if it rocks on the table. This would mean that the housing end is not flat and may not mate properly with the other half. Then I place a carpenter square on the table. This makes a straight vertical reference to measure from.
Then I place a another square against the carpenter square and set it so that the rule just touches the tube at differential case.
Clamp the rule in the combination square and check the tube at the bottom middle and top. Make sure that the carpenter square remains flat on the table. Then rotate the housing and check at another spot. I think this method will be good to about 1/32".
Others have made some jigs where they can chuck up the housing in a lathe and check the outer bearing with a dial gauge. This has to be the cats ass (behind), but I don't have that kind of stuff. Poke around the forum and you will find some excellent examples of the lathe method.
Matthew, the least worn bearings are found in the diff centre because here they are better lubricated and have far less weight on them. If the cage is tight then you could measure each roller diameter. Given a few to select from, chose those with the greater roller diameter. The closer to .5" the better. Wear on the ends of the cages, due to who knows what, is usually not a concern.
Hope this helps.
Allan from down under.
I have been reminded that the later housing had the filler holes lowered down so that it is impossible to overfill the differential. If you have the earlier rear ends, the correct level is an inch or so down. I use my finger to gauge. If I can feel the oil with the tip of my finger in the hole, it is about right.
Thanks for showing how you check your axle. I see how it works!
Allen, thanks for your input about the cages. I know that the outside bearings the wear on the ends of the cages is not an issue, but I figured for the inside ones it may be... If I understand you correctly that is not the case.
Neil, yes you are correct!
I was asked if this can be shared in newsletters and the such. YES!!! I figured the time I spent making this is worth it if it is helpful to others. Feel free to let me know if you find it helpful, but I don't need credit because I was just outlining what you will find in the MTFCA guide.