T18 Transmission noisy under load HELP

[cash667]

Hi guys,
Since I finished my Truck I did a couple of longer drives and theres one noise which scares me..

It comes from around transmission/clutch and appears only under heavy load conditions. You can hear it best in 4th gear when accelerating from low rpm. In this driving condition its loudest.
I didn‘t had the noise in 3rd gear, but when starting off at 2nd, 1st and reverse it‘s hearable but very quietly.
Heres a video which describes it best (in 4th gear):

https://vimeo.com/537287417


It’s kind of a grinding Noise, but no teeth grinding. More like two metalsurfaces rubbing on each other...
It’s a T18 manual transmission in a 2wd Truck. Clutch (12“) is completely new incl. Bearings and Flywheel surface.

The transmission shifts perfectly in every gear, up and down. No gears popping out etc. If you are in a little higher RPM in 4th gear and accelarate, there is no noise anymore. Just if you try to rapidly accelarate from low (1000) rpm.

I also checked if the driveshaft could have contact on something, as well as exhaust and engine when shaking under Road. But nothing at all...on every part enough clearance.

So I would appreciate any idea and help what this noise could come from.
I think I have to pull the transmission but I want to ask you guys before. Maybe some of you had the same. I kindly ask you to look into the video to get a clear idea what I‘m talking about.

Thanks!
Chris

[two-bit]

Um... yeah. Thats not right.
Great video to help all of us out. Thank you for that.
Going to have to think about this one .

[cash667]

Um... yeah. Thats not right.
Great video to help all of us out. Thank you for that.
Going to have to think about this one .

Hi two-bit,
I decided to pull the transmission and opened it, it found 3 things which could be a problem.

1. there was a slightly to long screw from the rear bearing retainer which looks like it had contact to the 1st gear.


I´m going to add a washer under these 2 screws to solve that.

2. I moved the 3/4 shift sleeve by hand to check if theres something wrong. When I push it into 4th gear and push it a little further to the front the following noise appears:
https://vimeo.com/538111225

It sounds very similar to what I heard when I was driving, don´t it?
It´s the 3/4 sleeve rubbing on the most forward gear of the countershaft. So the travel of this sleeve is limited by the shift fork. I installed the top cover with the shifter to check if the sleeve could move that far to the front when the shifter is in position 4th gear. It don´t! There is a little space between the sleeve and the countergear. I even wasn´t able to push it more forward with pulling on the shifter.
But I can imagine that if the input and output bearings ware worn, and the needles between input and outputshaft aswell, there could be some movement under heavy load conditions. What do you think?


3. the rear bearing is kind of loose in the housing which it wasn´t when I assembled the transmission last year.
https://vimeo.com/538113133

I know that it is secured by the snapring and the bearing retainer housing, but since I used kind of a thick (1mm) gasket on both bearing retainers the whole assembly could move about 1mm back and forth. And the question is again: what does it look like under heavy load?

So I think the noise I heard is a product of all 3 issues I found. Maybe I´ll find even more wenn I pull the in/out shafts..
So my plan for now is to get new bearings on the in/out shafts and new needles between them.
I checked if the countershaft could also move back and forth, but this guy seems to be stable because of it´s thrust washers on both ends. There is no real axial play in the countershaft.

I´ll also use thinner gaskets. In the shop manual they say to place the bearing retainers without gaskets and torque them slightly (!!) to check the gap with a feeler gauge to determine the correct gasket thickness. To be honest I wasn´t aware of that when I assembled the transmission first time

Any other ideas? Am I on the right track?

Hope the video documentation could help others as well if you hearing noises which you don´t know where they come from

[two-bit]

Great insights you found. I would do the needle bearings for sure on the shafts.
High torque load at "low" rpm can cause a lot of dual axis torque on shafts in a transmission.
ie: spinning rotational torque, and "side" load ("side" meaning : side to side, or forward and back.)
The shaft that 3/4 shift sleeve rides on could have extra movement because of worn bearings under "heavy" load.
Once the bearings get really worn, the shafts inside the trans can 'mimic a teeter totter action using the gears that are currently meshed as the fulcrum point. This will cause the gear mesh to be at the wrong angle and create a very ugly noise.
Many years ago, i remember something about bronze or brass components being used in the T-18, and not being used in the NP435. IIRC, the worn "yellow" parts supposedly broke down faster under high torque situations and created improper gear mesh under "heavy" load.
The fact that noise occurs "under load" ie: low road speed, high engine torque, and not at higher road speeds, makes me suspect that it is a torque transfer issue in the case. Probably a combination of worn bearings, and improper gear mesh as a result of worn bearings. Helical cut gears can be very noisy when they are not properly "aligned". Lots of mating surface there to make friction.

I don't think the screw shafts on the front are doing it. Instead of the washer, i have filed off the end of the bolt to the proper length, so it still has the full depth of thread to hold, just no extrusion past the face of the inside wall.

Your output bearing doesn't look that "loose" to me. Granted, i can not feel the side movement it may have, as far as in and out, i have moved output bearings on 18spd gear boxes in and out that freely. It was not an issue.

and yes. the whole feeler gauge correct gasket thickness thing, ya... you should do that

Not sure if i have helped you at all. I have spent most of my life repairing things, by being able to touch it and feel what its doing. Being that this gear box is literally half a world away, it makes it a bit of a guessing game for me.
I really do think you are on the right track.
Good luck.

[two-bit]

OK. Talked to a few more people. Went thru your build thread.
Engine timing, and rear diff were the two most common responses i got from people.
Since you already have gone thru the T-18 and the rear diff. We know its not there.
I did see in your build thread you reworked the curve on your dizzy.
Is it possible that this noise is a spark knock/pre detonation issue ?
It occurs at low rpm, most noticeable with heaviest load on the engine. (4th gear, 1000 rpm)
It does not happen once the engine rpms are higher in 4th gear. I am guessing 12-13 range it stops ?
You also said it very faintly occurs in 2nd when taking off. Could also be dizzy timing, but with the gear ratio in the trans the rpm comes up faster than it does in 4th gear. So its not real pronounced, or long lasting.

Maybe try to back off the dizzy a couple of degrees and see if it changes ? Maybe the dizzy is a wee bit to advanced for low rpm ?

A few others i talked to said it sounds like engine "lugging", and there solution was.... just don't do that. Lots of help there.

I really barked up the wrong tree with your T-18 rebuild. I thought for sure that was your issue.

Good luck ! and if all else fails... "just don't do that"

[cash667]

Hi Two-bit,
really appreciate your commitment on my noise issue!

I did a few thinks the last days:
I completely rebuild the t18 tranny, new bearings, rollers, thrust washers etc. All new except the synchro rings. I even put a new pilot bearing in the flywheel.

But the noise remains
Good thing is, the tranny is a bit quiter in overall operation.

So I would say this heavy noise is ONLY in 4th gear under heavy load, what I heard in 2nd etc is another noise and I think it´s a normal operation noise when releasing the clutch.

I did some more test drives and stuck my head out of the window to check how the noise sounds outside the car. As I did that I am pretty sure that I can locate the noise more on the back, I would even say it´s clearly coming from the center support bearing area of the drive shaft.
So that is why I think it´s not coming from the engine. It´s even no knocking noise in my mind...

So I picked the little GoPro camera of my girlfriend and mounted it under the Truck to see whats happening on the driveshaft when the noise occurs.
here´s the video:
https://vimeo.com/544249211

I think it is coming from the slip yoke or maybe from the rear axle. I first checked if all yokes are lined up in phase, but they were. The slip yoke can move also free on the splined shaft, but it´s got some minor play on it.

I jacked the truck up and put the 4th gear in and let it run. Here´s the video:
https://vimeo.com/544249734

you can hear sometimes a "clunk" noise, but I think thats from the backlash of ring an pinion gear and kind of normal when the tires are free spinning. But you can see a slight wobble around the left part of the rear driveshaft.

So could it be wear on the slip yoke? Heavy load causing it binding on the splines and prevent it from moving free back and forth on the shaft?
Could it be a slightly to short driveshaft? When disconnecting the driveshaft from the axle, you can slide the slip yoke another 1" to 1 1/2" on the splined shaft. How far is the yoke on the splined shaft on your trucks?
here is mine:

slip yoke.jpg

Distance end of yoke to bearing is about 2". Is that right or maybe to much?

You mentioned the rear diff- of course this could also cause that noise. I did not rebuild it, just checked for visible wear and put new gaskets in. But with my head outside the truck I would say it´s not coming from that far rear, but yeah...could also be delusion on my ears

I´m more and more running out of ideas what to ckeck to solve my noise problem. "just don´t do that" is the very last choice

Thanks
Chris

[two-bit]

Go pro video is great. The amount of axle wrap is really something to see. Real road conditions are always the best.
Questions...
1) Does the axle wrap like that and have movement on the slip shaft when shifting thru all the gears or only in 4th gear ?
2) You said you re-sealed the diff. Did you replace the front seal, if so, did you preload torque the yolk when you put it back on ?
3) Did you have the rear drive shaft tested for true ? ie: that it is straight ?
4)How much do you have going in to the rear shaft side of the slip yolk ?

Yes, it does look like the rear shaft has a bit of a wobble to it. I see it in the 2nd video, but not the first one.
Slip yolk looks like the right length.

The clunk, clunk, clunk in your second video has me concerned. Unloaded differentials usually do not make noises like that. I am correct that the noise is coming from the rear diff ?
Your drive shaft support bearing looks new and i didn't see any compression movement when under load. Good !
I doubt that it is bind in your U-joints, because the noise occurs when the shaft gets straighter. Not when it is angled.

If it were mine and i saw that on camera footage, i would be suspecting some thing involving the Ring and Pinion. Maybe when the axle rolls and the shaft gets straighter, it puts force on the pinion pushing it inward. Thus the tooth mesh between R&P gets tight and makes noise.
I would check for end play and side play on that rear pinion shaft.
I would also pull that rear drive shaft and have it checked for true. If you know some one with a lathe, maybe they can set it up in the lathe and you check the run out with a dial indicator on the shaft itself.

Need to find you a better option than, "just don't do that", with out spending to much more money.

[cash667]

I´ll first answer your 4 questions:
1) I dont know, but I will shoot a video of shifting through all gears showing the movement of the rear axle
2) I did not changed the front seal for that reason! I did not wanted to release the preload on the pinion bearings
3) no it´s not checked for true or imbalance, but I think if it isn´t true I´ll got problems and vibrations in all gears and especially in higher RPM. But yeah - if I can´t find something else I´ll find someone who´s going to check this for me
4) Do you mean how far the slip yoke slides on the splined shaft in mounted position? If so - I do not have an exact measurement, but I think it´s something around 3"-4".

here are some more videos from the slip yoke to show it´s play on the shaft:
https://vimeo.com/544650916
https://vimeo.com/544651400

Hard to see on the videos, I know...

About the clunk noise, to be honest I forgot if I located it more on the rear axle or on the slip yoke, I ´ll check that the next days. But in my mind it was kind of normal since you have allways a little play between ring and pinion gear. And the tires are spinning real easy free since there´s no contact from the brakeshoes in the drums.

When I do the next videos I´ll point the camera sideways to the rear axle yoke to see if it´s moving inward under load. I tried to push it in manually, but it won´t move a single millimeter that way.

I have to check if there are new slip yokes available for this truck and what it will cost. That will make the decision if it is worth to change it just to be sure.

[two-bit]

I have shared the video of your truck making "the noise" with a number of people. The resounding response is to much axle wrap.
Many of these people have commented that the rear differential rotates too much under load. That it throws off the pinion to drive shaft angle, possibly binding the rear u-joint.
Why you have that much axle wrap, i am not sure.
The leaf springs on your truck , (in the video), look like they have too much flex, allowing the differential to rotate. I looked at your pics in the build thread. It looks like everything is assembled correctly.
I am not sure what advice to give you from here.
Got anyone local to bounce some ideas off of ?
I will do some more digging here in some of my service manuals about differential deflection rates, and proper pinion angles.
I did notice you have the Flex-o-matic spring shackles. I am not familiar with those and there intended design idea.

As far as the slip yolk on your drive shaft. I have seen worse. We have a saying about spline shafts. If the drive side of the tooth looks like a ski jump. Replace it.
ie: both sides of a tooth should have a slight convex shape to them, if one side is convex, and the other concave, it will cause excessive tolerance between the "drive" side of the tooth and the "driven " side of the next tooth. That causes slop/play/and bind in a slip joint.

I would get the axle wrap issue figured out. I think most of your problems lie there.
Good luck Chris.

[two-bit]

https://www.diyford.com/ford-restomod-r ... ion-guide/


I got this link from a builder friend of mine. He does all kinds of radical stuff. Hope it helps.
Looks like there is lots of good, solid, info in this article.


Two-bit

[cash667]

Thanks for the link! That´s a very interesting topic!
I also ask the classic ford community in germany but nobody had a similar issue or a good idea to solve it.

As I said I did some more videos today:
take off through all 4 gears:
https://vimeo.com/546146000

and here´s again the 4th gear acceleration thing:
https://vimeo.com/546147033

But I was able to force it to make this noise in 3rd gear aswell when trying to accelerate rapidly out of low rpm. I think the more I try to force the noise at test drives the worse it became...
And yes, there´s a lot axle wrap in all gears, but everything on the leafsprings seems to be ok. Maybe they are worn?

I also did another shot of the rotating rear driveshaft and there is some imbalance, it seems not to be true in the middle part:
https://vimeo.com/546147840
The "clonk" noise can´t be located to the rear axle for sure, me ears told my it´s more on the driveshaft itself or on the slip yoke, really not easy to locate.


As I read the pinion angle article I decided to measure all my driveshaft angles. Here´s what I got:

IMG_8938.JPG

And I feed the angles into the spicer driveline calculator:

Driveshaft angles.jpg

Regarding to the article this is not what I want to have. I need to get the rear axle pinion more down.
But I also would like to know if the other angles are good? Can´t find good information on the shop manual..
Is the coupling shaft (first driveshaft) supposed to point kind of upward in relation to the transmission outputshaft?
I found in the drawings that a 390 engine has a down tilt at about 5,7°, I measured 5,3° which I think is ok (keep in mind I got a 460 in it)
But should the coupling shaft remain on this angle? If yes I need to move the center support bearing down about 1". This would also help to equalize the operating angles of joints from the second drive shaft.
I could also add some degree shims under the leaf packs to get the pinion more down.
What do you think, right path to move on?

I wont add any tractions bars...there must be another solution for this issue.

[SBR_GUY]

I have a T18 trans for sale. It has a fresh rebuild on it done by Kenny Brown of Browns Transmission in Ventura California.