Well, as I took my Rear End apart and saw the horrors inside, I knew the right thing to do was rebuild the Drive Shaft at the same time.
I unbolted it from the rear differential and started looking it over. The first thing was to remove the Cotter pin from the nut holding the Pinion Gear. I did that and to my surprise the nut was already loose. I removed it with my hands. I was really expecting about 75 foot pounds here so something was not right. How much play should the pinion gear have when mounted loose with the key on the Drive Shaft? Mine has some play, when twisting the gear. Not sure the true amount but a guess would be about 1/32 or a little more. Is this acceptable or should it be solid with now play side to side?
You can see the rut pits in the Inner Pinion Bearing sleeve.
The bearing housing came off with the original hyatt bearing. The pinion bearing housing looked great with no wear groove from the bearing but it did have a nice rust spot with pits about the size of a dime. The Hyatt bearing looked very worn out. You could see where the rollers were wearing through the cage near the pinion end. The cage was loose, and it had the same rust spot to match on the rollers.
The Drive Shaft thrust bearings looked good as did the two bearing races. What are peoples thoughts on the Fun Project Bearings. Is this a good way to go and do I use the thrust bearings as is?
The front end of the shaft is where the babbit bushing is. What is an acceptable shaft diameter for the front bushing? Mine measured 1.025 as near as I can tell. Does this sound right?
I should mention that I removed the two caps covering the U-joint pin and I tapped that out. I did that with ease and pulled the U-joint out and the shaft from the housing. What is acceptable here? How can I give the U-Joint a good exam and check to see if its serviceable?
Thanks for looking and giving your opinion here. It really helps me understand and evaluate the parts I have and others I see.
I highly recommend using the Fun Projects pinion bearing setup. It's invisible from the outside, fits, works, and everything lines up right.
The key must fit with no slop in the drive shaft or pinion gear. As it had run for some time with the nut loose, the keyway may be shot in the shaft. If so, replace it. You may be able to find a good used drive shaft if the budget is snug.
I don't recall the shaft diameter for the u-joint end but the brass/bronze bushing compresses some when you press it in so if the shaft is smooth on the upper end and you can get a nice fit in the bushing, all should be fine there.
The u-joint looks a bit sloppy but what I would consider usable. Other opinions may vary.
The Fun Projects bearing replaces both the Hyatt and the thrust bearing. In my experience it's hard to find a good drive shaft Hyatt and the solid roller replacements is a failure waiting to happen, so the Fun Projects bearing is the way to go IMHO.
You need a new or better pinion gear. If the play to the key isn't gone with the replacement pinion you'll have to get a new key too. Maybe you can grind the cone on the drive shaft to get a good fit to the new pinion with some valve grinding paste?
Cut the inner hyatt race lengthwise carefully with an angle grinder or at the friendly local machine shop like Steve Jelf did in a recent thread - they're hard to pull off the driveshaft with common pullers without cutting them first. Don't cut into the drive shaft.
It's hard to see the play in your u-joint, what first looks like excessive play turns out to be a shadow. It may be ok? How does it feel?
Walt is likely right about the keyway being enlarged in the driveshaft by the loose pinion turning from one direction to the other depending on acceleration or braking. In that case you're looking at replacing the driveshaft too.
Pinion, ujoint are shot. Inner sleeve, thrust bearing and the spool look good. At least in appearance. Don't fuss about the minor pitting. I strive for 3 thou or less clearance on a rebuild once the spool bearing is inserted between the spool and the inner sleeve. I think the new spec on the bearing rollers is .562", but I am going from memory. If you have excessive clearance, replace one or all of the components. The front end of your drive shaft shows wear, I would replace it, but you can file the edges where the ujoint goes so it will fit inside an upper bushing with an undersize ID. I strive for 3 thou or less clearance in the upper as well.
I too will cast my vote in favor of the Fun Projects pinion bearing kit. I've used several and like them a lot. To test the U-joint, grab both ends in your hands and twist them opposite directions. If you can feel slop in the joint, get a better one. Trial-fit both ends to the parts they mate with. If they are sloppy, replace it. If snug, you're good to go.
Here are some more pictures of a few of the parts.
How much play in the U-Joint is acceptable? Here, these pictures show the gaps a little better than the first pictures did. I know it would be allot easier if the U-Joint were in your hands to evaluate but is there an acceptable limit or is zero play the goal here. Maybe one of those parts that while your there change it out or maybe its not.
The next picture is a close up of the pitting damage in the Pinion Bearing Housing.
Should I toss this part and go with the Fun Projects bearing given that my Hyatt is shot? My thrust bearing looks good but am I right in that you do not use the thrust bearing in the fun projects Bearing Upgrade? Do you have to take off the inner Pinion Bearing surface to use the Fun Projects Bearing?
The real question is, can I reuse my Drive Shaft? What do I need to look at to qualify or disqualify the Drive Shaft? The Pinion Nut was loose on the shaft when I took it off so that scares me a little. When I put the pinion and key on the end of the Drive Shaft it does have some movement side to side. That in its self might be a disqualifying factor but I'm not sure.
What is the measurement that I am looking for on the front bearing surface of the Shaft for the Bushing?
Are the New Drive Shafts as good as originals. I read that they might not be as hard as originals but are allot more true and straight.
Allot of questions here, sorry about that but hopefully I can get some idea of what to keep and what I need to look for.
Every T owner has his own likes and dislikes. I've used nothing but original genuine Ford parts ever since I started in this hobby, and see no reason to change now. It all depends on how bad you want to find the original parts.
Those pits in the pinion bearing housing mean nothing. They're from a bit of rust and not wear. If all else looks o.k. I would reuse it.
I just had to get a new drive shaft for my 1919 Touring. The pinion was lose and with all the flopping around the key slot was worn just like yours...you'll never get the pinion to fit tight without getting a better shaft.
I'm with the revisionist crowd that prefers the FP pinion bearing. Here's the sleeve removal Roger mentioned. Just cut the length of the sleeve, being careful not to cut through into the shaft. After that just a few whacks with a hammer will remove it.
On second look, I agree with Roger. What looks like excessive play in the ujoint is a shadow. It may be fine.
I pulled my rear end apart after hearing some very nasty noises. I discovered that the replacement (smooth roller) bearing cage had collapsed jamming the drive shaft.
Replaced it with a Fun Projects, had some adventures getting the shaft to not hit the spider housing but now it is wonderful.
While I was at it, I replaced my smooth axel bearings and sleeves (sleeves were very worn) with the original Hyaats and sleeves. I should never have changed them in the first place.
All very good now.
Many people forget about tolerances, clearance and wear when overhauling a Model T Drive Shaft Roller Bearing Assembly. The result can be either an assembly at is literally to tight to fit, or one which allows so much slop in the pinion gear as to make it almost impossible to get the correct clearance between the pinion and ring gears.
It is sometimes amazing to me what you can find in Acc. 1701, the Parts Drawings collection at the Benson Ford Research Center. One time while looking through a number of rear axle and drive shaft drawings I ran across a drawing labeled T-190 Drive Shaft Roller Bearing Assembly. The beauty of this drawing is that it shows each part in the assembly in relation to one another and their minimum and maximum sizes. There is also a nominal size for each part that the Ford Engineers were shooting for.
It is virtually impossible to make two parts exactly alike. It is possible to get very close to alike, but if your measuring tools are able to measure to a high enough degree of precision, you can find differences in the parts dimension.
The secret to making interchangeable parts is recognizing that minute differences in dimensions do occur and to allow for it. Part dimensions must be specified in terms of a tolerance, that is a minimum or maximum size. As long as each part remains within it's respective tolerance, all of the parts will fit together correctly.
I think that Mr. Ford and his assistants had a thorough understanding of tolerances, and what degree of tolerances were acceptable, and could be efficiently produced with the technology available at the time. Mr. Ford also understood the need for clearances to allow space between
parts for a film of lubrication. All of this must be understood and allowed for when designing the parts.
There are effectively four parts whose dimensions are critical in the Drive Shaft Roller Bearing Assembly. First is the Drive Shaft Roller Bearing Sleeve. This is the bearing that slides over the driveshaft and which provides inner support for the Drive Shaft Roller Bearing. This is suppose to be a very tight fit on the driveshaft, and it usually must be pressed or driven on. The Stevens, New York drive shaft sleeve driver is probably the most effective way to drive the sleeve on. The Roller Bearing Sleeve has a maximum and minimum outside diameter of 1.247-1.249 inches.
The next two parts whose dimensions are critical are the Drive Shaft Roller Bearing Rollers themselves. These spiral rollers were made from chrome vanadium steel, and ground to a tolerance of 0.561-0.563. In fractional terms, the nominal size was 9/16" or 0.5625. When rebuilding a Driveshaft Roller Bearing Assembly it is important to measure the diameter of the rollers. Most show substantial wear and will measure 0.560 or less. Sometimes a lot less. Before concluding that .003-.005 undersize is acceptable remember this: the roller on the other side of the bearing will show an equal amount of wear, and your bearing assembly has been worn not 0.003-0.005 undersize, but twice that or 0.006-0.010. The Driveshaft Roller Bearing can make the assembly very sloppy very quickly.
Finally, there is the Drive Shaft Bearing Housing, or spool. Again, the Ford Engineers specified a minimum and maximum side for the ground interior surface that the Roller Bearing rolls against. This part carries the factory symbol number T-191-C. It appears that the engineers wanted the nominal diameter of the interior surface to be 2.375 inches, and set the minimum and maximum diameters to be 2.374-2.376. Drive Shaft Roller Bearing Housings wear a lot. Using a good inside micrometer, the housing diameter will be 2.376 or larger. Sizes of 2.380 or larger are not uncommon, and while a housing may look good, you really don't know what it's condition is until you have measured the diameter of the housing.
Model T Drive Shaft Roller Bearing Assembly
T Number Maximum Minimum Nominal
T-163B 1.249 1.247 1.248
T-107 0.563 0.561 0.5625
T-107 0.563 0.561 0.5625
Sum 2.375 2.369 2.373
T-191C 2.376 2.374 2.375
Clearance 0.001 0.005 0.002
I created the table above based on the dimensions found on the T-190 drawing. The first column lists the factory symbol number for each part. A single roller bearing roller carries the factory number T-107. However, there are two rollers for dimensional purposes (one on each side of the drive shaft) so the T-107 is counted twice. The second column shows the maximum dimension of each part. The minimum dimensions appear in the third column, and the nominal dimension are in the fourth column. The sum of the dimensions of the first 3 parts is in the fourth row. In the fifth row are the dimensions of the Roller Bearing Housing, and the bottom row is the clearance between the first 3 parts and the Roller Bearing Housings.
As can be seen from the nominal size column, the assembly was designed to have a 0.002 clearance, and that is what I try to achieve when selecting the parts for an assembly. With a 0.002 clearance the pinion bearing will have no discernible slop, the pinion gear will run true with respect to the ring gear, and there will be sufficient clearance for lubrication.
The two other columns are in effect extreme cases. If every part was at its maximum dimension, then the resulting clearing would only be 0.001. On the other hand, if every part was at its minimum dimension, then the resulting clearance would be 0.005. Actually, there is a worse case scenario in which the first three parts were at their minimum dimensions and the were combined with a Drive Shaft Housing that was at it's maximum allowable diameter, in which case the total clearance would grow to 0.007, which is pretty sloppy. You can rock the pinion gear against the assembly and clearly feel the movement.
In reality, if the machine tools were properly adjusted, the parts of the assembly were most likely very close to their nominal dimensions. The typical clearance between the assembly's parts when new would have been 0.002-0.003.
Getting to a clearance of 0.002-0.003 when rebuilding a Model T Drive Shaft Roller Bearing Assembly today can be quite challenging. The only acceptable new part is the Drive Shaft Roller Bearing Sleeve. The new sleeves I have been getting have measured a consistent 1.250 outside diameter, and this is good news. That slightly larger diameter will take up 0.001 of the wear in the other 3 parts. Still, the rebuilder has to find a Drive Shaft Roller Bearing and a Drive Shaft Roller Bearing Housing that are close enough to their original dimensions to keep the clearance of the assembly together within 0.002-0.003.
Good parts are becoming increasingly difficult to find. Like my friend Larry "Original" Smith, I have a few good assemblies set aside. But it is clear to me that the days of using original style parts are coming to a close. An alternative solution needs to be found.
I think that the Fun Projects replacement roller bearing assemblies are the solution. I have used them before with good satisfaction. The FP design, using tapered roller bearings, also eliminates the use of thrust bearings, and facing the end of the front driveshaft bushing to a precise dimension is no longer necessary. They will greatly reduce/eliminate any slop that might otherwise keep the pinion gear from running true with the ring gear.
On the drive shaft of my 1914 Touring I find also the nut of the pinion nearly loose even if the cotter pine looked original and the pinion was very easy to remove. The key ways and the key were OK.
Does that mean that the shaft is extending ?
Wow Trent, that was a great read. Thanks for taking the time to write all that up! I have copied this for my records. It really opened my eyes as to what I am looking for in good used parts.
I am off to do some measuring to see where my worn parts shake out. It will be good for me to practice and to see just how bad these parts really were.
Hi Philippe, Model T drive shafts do not get longer with age. But parts do wear and everything is subject to vibration. Variations in the road surface, hills and valleys also put stress on the pinion, the driveshaft, and the drive shaft roller bearing assembly. Vibration alone can make the parts move around a bit over 100 years. One place that substantial wear can occur is the point where the drive shaft roller bearing sleeve contacts the thrust bearing plate. The wear can be quite extensive and this can cause the pinion to move up toward the u-joint 0.010-0.020 inches. This tends to put strain on the teeth of the pinion and the ring gear.
Going forward, you just need to measure everything with a good inch micrometer, and start searching for the parts that are no longer serviceable.
Wonderful info, Trent. I have printed it out , too. It is almost like you are a professor or something! tim
Thanks for posting the info. I probably would only add that usually the later spools are not only worn oversize (>2.375) but also very often they are out of round because of the random application of the load both during acceleration and braking. In the same way that brake drums can be worn out of round so can the drive shaft pinion spool. Thus it is a good idea to measure the inner diameter at several places around the perimeter of the spool before reusing it and check it carefully for cracks which usually occur in the ring portion that inserts into the differential portion of the rear end. The spools are almost always worn into a funnel shape with the rear most diameter being larger than the forward diameter near the thrust bearing. There is nothing wrong with the original design except that nobody is making the hyatt bearing roller assembly.
If anyone has some NOS hyatt bearings - I have a few NOS rear spools of the later open type (1922-1927). They are still in original cosmoline or whatever it is that Ford packed them in. They measure exactly 2.375 at all points along the bore and they very obviously have never been mounted.
I cast my vote with the revisionists as well. John Regan's set-up makes correct installation of the pinion gear and supporting bearing incredibly easy for even a rookie like me. The added benefit is that you don't have to be super fussy about reaming the torque tube's bearing face like you do with the traditional assembly.
John's point about the uneven wear patterns in the Drive Shaft Roller Bearing Housing is spot on. They wear tapered, they wear out of round, and they must be precisely measured in several different places. The Drive Shaft Roller Bearing itself also wears unevenly. One end of the rollers themselves will wear substantially more than the other end. For example, one end of the rollers may measure 0.560, but at the other end it's diameter might measure 0.557. In addition, the wear on individual rollers on the same bearing assembly may be different as well.
The lesson here is, in the absence of New Old Stock parts, the Drive Shaft Roller Bearing Housing, and the Drive Shaft Roller Bearing must be precisely measured in several different places when evaluating whether to return them to service, or replace.
Good used parts are becoming increasingly hard to find.
What Trent says about the varying measurements among rollers and at opposite ends also goes for the axle bearings. When it comes to those, is the greater wear at the inner end, or outer, and is the wear pattern the same for inner and outer bearings?
The outer axle bearings wear more on the outside end. The inner bearings wear very little, and pretty much evenly, from what I've seen.