I've recently assembled a 3.33 differential for my '25 Coupe and it howls, worse at low speed and even worse when decelerating to a stop. Basically everything is either excellent original,or new (reproduction). This is not my first rodeo, and I've not cut any corners to save a few bucks so I'm a little disappointed that after all my efforts and expense (around $1,000.00), I have a rear end that is not anywhere as quiet as the old one I removed (standard 3.63). The excellent original pieces include the u-joint,driveshaft and driveshaft housing,the Hyatts,two outer sleeves,both axles and axle gears, spiders,carrier halves,spacers on both sides of the bronze thrust washers, and the actual housing halves. The reproduction parts include the u-joint pin,a new pair of bronze thrust washers, both inner sleeves and a 12 tooth pinion from Don Lang, a newly available 40 tooth recessed crown gear from Glen Chaffin, and a new non-adjustable pinion bearing set-up from Fun Projects. I spent a lot of time double-checking all the measurements/clearance specs etc following the Chaffin guide. I set the C/P clearance at 0.010 (yes, I checked at at least 10 positions around the circumference), but could still feel tooth contact at every tooth when turning the assembly over with the u-joint. Needless to say the diff. howled, fairly loud at lower speeds and way worse on deceleration when coming to a stop. I have since added shims between the pinion spool and the rear end housing, maybe 0.015" at a time to establish more clearance between the crown and pinion and each time the howl diminishes somewhat. I now have 0.090" of shimstock in there and the howl is way less, but still there. By my calculations 0.090" of shim increases the C/P clearance by 0.0347" so when added to the initial 0.010" I now have 0.044". I'm sure that this condition has been discussed here before and I don't want to waste valuable thread space but would appreciate advice or help either here or by PM. Thanks in advance : Bruce
Bruce - how many miles has it been driven so far? If only a few I would just wait a little bit and it will probably quiet down.
Is Chaffin's new gear meant to be used with the 12 tooth pinion? I always understood that the 12 tooth was used with a 39 tooth ring gear to get 3.25, I was not aware it was compatible with the pitch of the 40 tooth gear.
Bruce, The 12 tooth pinion and 40 tooth ring gear are manufactured by the same gear cutter and have the same pitch. You state that you had 0.010 in clearance and still felt the teeth cogging. This is impossible. I assume Lang bought the 12 tooth pinion from us. If he bought it elsewhere that could be a problem. please check and make sure he bought it from us. When the pinion is fully meshed with the ring gear the toe of each gear has between 0.030 -0.050 clearance so there is no contact of the toe in the valley of the teeth. The only thing making contact is the sides of the gears. Yes you will get noise if you do not give the gears clearance. With 0.010 in cl;earance you should be able to turn the gears with no noise. You should also be able to rock the ring gear back and forth with no contact of the gears until you hit the side of the pinion which is stationary. There should be absolutely no drive shaft end play as this wiil affect the clearance.
If you read the book, you must mount the differential assembly in the passenger side housing sitting vertically. you then mount the Drive shaft to the housing first checking to make sure there is no end play. Then check the ring gear and pinion clearance. If you have 0.010 clearance you will not feel the gears cogging or hear any noise. If you are using a new bearing pinion spool assembly. Never rely on the lock ring to hold end play. This is the most common mistake people make. The lock ring can come loose. Set the lock ring and then set end play the same way you would normally by adjusting the clearance between the back side of the U-Joint and the Drive Shaft bushing. Be sure to install the pin. There should be no end play. Tap on the end of the U-joint with a small hammer and see if the pinion moves back and changes the clearance.
Andy, Both the 12 tooth and 13 tooth pinions can be used with both the 39 and 40 tooth ring gears.
You can't simply set bevel gears by measuring backlash. You have to check the contact pattern with either white lead or Prussian blue and move the pinion or ring gear accordingly.
Its not sufficient to run paper thru the mesh if you want a quiet rear end. There are those who will disagree with this and everyone is entitled to their opinion. Google "bevel gear contact pattern" for more information.
Thanks for the response Glen . As you probably recall, I phoned you after hearing the howl initially and discussed clearances and what you refer to as "cogging" and you suggested that the lock ring on the pinion bearing assembly had come loose . I'm having trouble understanding this as I tightened the lock ring allen head bolt to the point that I thought I might strip it or snap the allen key. As well, I'm using a near mint original u-joint,driveshaft and driveshaft housing. The u-joint is pinned and the original driveshaft bushing to driveshaft clearance is less than 0.002". With straight cut gears, any force created by these gears in either direction is trying to push them apart, not pull them together and eliminate any pre-set clearance. As for the 0.010" C/P clearance that I had initially, I could visually see it, accurately measure it,as well as feel it and hear it. I could also clearly see that the teeth on either gear did not bottom in the valley of the other. I should also add that I had to install 0.025" if steel shim under the crown gear to get the 0.010" clearance. Upon assembly the unit did have the "cogging" feel when rotated by the u-joint. Obviously all this was checked with the diff. on the bench so there was absolutely no force trying to shove the driveshaft and pinion back into the crown and diminish the pre-set clearance. I'm still confused. Cheers : Bruce
"You can't simply set bevel gears by measuring backlash."
THANK YOU! Been trying to tell people this for years and have been consistently ignored.
bruce, I am checking the gears. We have never had a problem before but there is always a first time. Will let you know what I find Glen
One of my first jobs when I went to work at the port was to replace a set of bevel gears in a 90 degree gearbox on a large outdrive with a 40" propeller that was mounted on a barge used to pick up trash in the harbor. The drive had been installed in about 1972, and I was told that the gears would only last about two years before needing replacement because they couldn't stand up to the abuse from the big prop. There was an oil pump that circulated oil through the unit and over the gears. After about two years the boat pilot would notice that the oil pressure had dropped to near zero due to the wear from circulating all of the metal worn from the gears, and they would pull the unit and bring it into the shop and replace the gears and oil pump and put it back on the barge.
Shortly after going to work there in 1991, it was time to replace the gears again, and this time they gave the job to the new guy (me.) They gave me the new gears and oil pump, and a pile of old leftover "gaskets" from all of the previous years. One of the old-timers told me to just use a couple of the gaskets and some silicone and bolt it together.
I asked about contact and was given a shrug of the shoulders and told there wasn't any adjustments. The two gears were the same size, and the old guy told me "it's not like a ring and pinion set-up." I quickly realized that the "gaskets" were actually shims. There were white ones, blue ones, and yellow ones, and they were different thicknesses. It was a lot of work and heavy lifting to take it apart and put it back together multiple times, and they thought I was crazy for spending so much time on an old barge that would be back in the shop in a short time ("those gears just don't last"), but I finally got a pattern and clearance that I was happy with, like a ring and pinion pattern.
Twenty-five years later, and those gears and oil pump are still running in that unit! Proper set-up, not just clearance, is essential.
Hi Bruce, Check that the allen screw on the caller is not too high,and hitting the tube. I had that problem, took a file to it. Don
I suspect that you have the pinion depth too deep. May require extra gaskets on the spool to move the gear forward. Then you will have to shim the differential thrust to get rid of the excess side play.
Don makes a very valid point. Check the Allen head lock bolt on the collar as I recently installed a modern replacement spool assembly and experienced a clunking sound coming from the drive shaft assembly. The result upon further investigation was determined to be the head of the Allen head set screw coming into contact with a casting formation protruding down into the inner portion of the tube rear sleeve mounting plate. After removing the anomaly and grinding material off the head of the screw, the clunking sound was eliminated. Happy hunting.
"I suspect that you have the pinion depth too deep."
Anyone can suspect anything they want. Until the contact pattern between the mating teeth is observed, it's all just "suspicion", i.e. guesswork.
If you don't believe me, listen to Dan McEachern. I suspect he's smarter than me.
Totally agree - easy to check using a dab of Lubriplate or red bearing grease. Or any number of other ways. You should be able to achieve .010" clearance +0 / - .010" and be able to "feel" a smooth rotation of the assembly before installing it in the car.
One drive around the block and the bronze washers will wear in, and then you will have a few thousandths more clearance than you started with.
Breuce, There is nothing wrong with the new 40 tooth ring gears. However, We have made hundreds of these 12 tooth pinions and have had no problems. I just checked the new batch and there is something wrong. It is normal to get a small amount of cogging when you have no oil between the gears. However, this batch of gears is too loud. I will take them back to the gear maker tomorrow and have him check them. If th3e gear you bought from Lang's is one of ours we will replace it. So pl4ase let us know if it is one of ours. We have had several dealers copy our products so I need to know if it is ours. Will keep you posted
Thanks Glen : I very much appreciate your offer. I talked to Steve Lang today while putting in another order, and he assured me that the 12 tooth pinion they supplied to me was in fact one of yours. Apparently they had used another supplier that stopped making them in 2014, and they (Langs) were out of stock for a while. I'm curious to hear what your gear maker finds, and wondering if the one I have will wear in to the point that the howl stops as I don't want to tear the car down again till the Fall before I put it away. Cheers : Bruce
Sorry for just stepping in here, but I'm curious Glen, are your gears marked in any way?
Bruce, We have sold 32 of the gears I sent you and have had no complaints until now. Apparently the noise is diminished when run in heavy oil. But that does not mean there is not a problem. The gears should run quiet. We appreciate your letting us know so we can determine what went wrong. We pride ourselves on the quality of our products and certainly want to fix any problems.. Charles, no our gears are not marked in any way.
Bruce, If the gears wear in they are to soft and will wear out very soon. If they are cut wrong they will never work as you want. Its not like breaking in a new pair of boots. A good gear will be very quite and will give many years of service if set up right.
Don and Mark: I did check for contact by the head of the allen head bolt that holds the lock ring, and there was minor contact. I had to remove some material from the welded area inside the driveshaft tube to establish safe clearance. The noise I'm getting though is a howl, not a clunk that would be heard once per rotation of the driveshaft. Thanks : Bruce
Bruce, Please send us the 12 tooth pinion, we will have it reworked or replace it. We want you to be happy, Glen
And there you have it.
What an OUTSTANDING vendor!
I agree Craig. Glen; thanks again, but I have plans to use the car till maybe September and also really don't want to have it parked in my one-car shop for a week or two as my other old car, a '54 Merc will have to sit outside . Is it OK to wait till then. Actually, I call you this week so we can figure things out. Cheers, and thanks again : Bruce
Bruce, Driving with the bad 12 tooth gear will hurt your ring gear. You will have to replace both of them if you keep driving it. Scott
You're right Scott. I tried Glen today but couldn't get through (he's a busy guy). Will try again tomorrow. Bruce
Just to update this saga, I did call Glen early in August and as suggested, did send him my 12 tooth pinion. Upon examination, he and his "gear guy" determined that the teeth were too wide on the pinion and that it could be re-worked and returned to me as soon as the fellow could get to it. I realize that Glen has a great reputation and that his gear guy probably is busy, but it's been five months and my dissassembled differential is still sitting on my shop floor (covered up), and I'm beginning to wonder. As I already have one of Glen's new recessed 40 tooth crown gears, my question now is: does anyone out there have a decent used 12 tooth pinion for sale? We are off to Florida around Christmas, so there is no panic as it won't be going back together till April at the earliest but I want to have something to assemble then. Thanks : Bruce
There are few people out there willing to make parts for the Model T Ford. When you find a source you must be patient. They have to work it into their schedule as they have other jobs that pay a lot more money than the Model T hobby. So it is either be patient or loose your source of parts. We cannot afford that or you will never get your parts. Please be patient or we can just refund your money.
Seriously? 5 months? How long would it have taken to replace it as you said you would above?
Why don't you put it back together with your good 3.63 ratio gears and get it back on the road?
One would have to assume that either Chaffin is out of 12 tooth pinions or all he has are defective, otherwise, I am sure he would have sent you a replacement.
Five months is outrageous. Demand he send you a good one. This bit about having it reworked is bunk.
Have more of these gears been sold since Bruce bought his and are there problems with them also? I've never had a reason to deal with Chaffin but I've only read good things about him here so I can;t help but wonder what's going on BUT if I read what he's last posted about my order from him I'd be seeing double for sure.
In Chaffin's defense, I have had a similar experience with suppliers.
I used to make antique airplane wheels. A couple of key components were made by metal spinning. The components were far from trivial to manufacture, and required a really top notch shop. The shop rate and minimum order size for the shop that could do the job were far beyond my reach. But the owner of the business made me an offer that worked for both him and for me.
The spinning shop occasionally had a gap between larger jobs. The owner didn't want to lay off key people of course, so he said he would give me a call when he saw a slow time coming. If I could fill his work gap with an order, he was willing to do my job. Mind you, even his "slow time for a small order at reduced price" amounted to $10,000 to $15,000 at a crack.
My point is that it sounds like Chaffin's is in a similar situation. Glen simply isn't in a position to make immediate demands to on a big, highly capable shop. And yet the part that he needs requires nothing less than such a shop.
Whoa guys, I'm not out to crucify Glen or his "gear guy" as I realize the value and importance of having guys like them contributing their efforts to keep our toys on the road. Just the opposite, as Glen has been more than cordial in our conversations and more than once has offered a refund. To answer a previous posting, I already have a silent 3.63 rear end in the car and had built up the 3.33 from N.O.S and repop parts so I could exchange the rear ends and not have the car tied up on the hoist for a week or two. The reality is that I really want to run the 3.33 ratio in my Coupe and I'm now prepared to wait till spring to get the parts to put it back together. My biggest concern is that I still may not have a useable 12 tooth pinion by then, and that is why I was asking if anyone had a good used one for sale. My take on the defective pinion is that Glen received a "bad batch" of gears (as he stated in his posting of July 28th) and probably has none left from the previous batch so has to have new ones made. Now he is at the mercy of the "gear guy" who probably has better things to do than correct his mistakes. In the meantime, to protect his already great reputation Glen won't send another "bad" pinion and must play the waiting game and hope for the best. The bottom line for me is that I really want a serviceable 12 tooth pinion and will settle for a nice used one if I can find one. Cheers : Bruce
Bruce, I was looking looking over the parts on my shelf yesterday and I have a 12 tooth pinyon that I have no plans to use. Send me a pm with a mailing address and I will send it to you. Not sure what it and shipping is worth at this time.
Thanks Dale : Sent you a PM. Bruce
WOW! If you read this entire thread carefully, especially the info exchange between Bruce Compton & Glen Chaffin, this is an excellent demonstration of what this forum is all about! The forum is always entertaining and informative, but also a terrific asset to our hobby in that here is an example of how the forum can be used to help toward improvement of replacement parts when vendor, manufacturer and consumer all work together to correct and improve an important replacement part! Makes me proud of the Model T Ford community as a whole! Thank you Bruce & Glen!
And thank you Harold S!
Yes, Thanks Harold. This has to be the best forum ever with lots of ideas, opinions, and offerings of knowledge gained through many years of experience messin' with Model Ts. This fall at my spot at Hershey I was able to finally meet several forum contributors including Dean Yoder, Steve Jelf and the fellow from Birdhaven as well as several other fellow "forumers" that all had great things to say about this site. Cheers : Bruce
More to follow!
Hey Bruce,....good one! I learned a new word! ("FORUMERS") I hafta' say,.... I think I'd rather be a "forumer" than a "blogger"! (.....altho' it IS harder to say)..... harold (:^)
The gear cutter assures me that he is working on the problem in his spare time of which he has little. I am just as frustrated as you are but have no control over the problem. I cannot afford to complain much because I will loose the source and that would be bad. Please be patient. Thanks, Glen
Hi Glen : I understand and appreciate your situation, so I'm OK till mid-March and hopefully something will happen by then. In a perfect world you could send the new/repaired pinion to me in Florida so I'd be all set to reassemble things when I get home. Thanks again : Bruce