Advice required on 5 speed gearbox rebuild.

A while ago I replaced all the 3rd gear components apart from the 3rd gear bush in the 5 speed.
All the gears now shift nicely with no crunching. There is though an issue when I shift from 2nd or 4th into 3rd.
As I release the clutch pedal upon selecting 3rd gear there is a whirring noise,that sounds like a bearing or bushing spinning,
that then goes away when throttle is applied.

All the internal bearings were replaced apart from the diff bearings. The clutch and release bearing were also replaced.
I have it apart at the moment to replace the 3rd gear bushing to see if that is causing the issue and I would appreciate any thoughts as to what
it may possibly be. I have attached some photos of the 3rd and 4th gear bushings and would be interested to know what people think may be the source of the noise or what the wear patterns indicate. . Also advice as to whether the diff bearings look worn and should be replaced.
Thanks
Peter
IMG_4410.JPG

the wear patterns may indicate.
Thanks
Peter

IMG_4415.JPG
IMG_4416.JPG
IMG_4415.JPG
IMG_4416.JPG
IMG_4415.JPG
IMG_4416.JPG
IMG_4424.JPG
IMG_4425.JPG
IMG_4426.JPG
IMG_4427.JPG
IMG_4428.JPG
IMG_4429.JPG
IMG_4412 (1).JPG
IMG_4413.JPG
 
On further examination of the parts I noticed that the detent spring for 3rd gear has lost its tension. I will replace this and hope that it may be the cause of the 3rd gear noise that I'm chasing. Can anyone tell me what effect this stretched spring may have on the operation of the gearbox.
Thanks
Peter
 

Attachments

Dan Sarandrea (Phila)

Waitin' On Parts...
As I understand it, the bushing itself is not supposed to rotate on the shaft, so any indication thereof, either on the shaft surface or the inner bore of the bushing, that it is doing so, is an indicator of some problem (maybe insufficient torque on the end nut of the shaft, or too much resistance in the fit between the outer surface of the bushing and the bore of the gear).

To my untrained eye it is not showing signs of spinning, but that and $1.89 will get you a small coffee at Dunkin'. LOL

I would think if the spring tension on the detent ball(s) were well under spec, the first symptom would be the trans popping out of gear. I had that problem after rebuilding mine, the springs are different (two of one and one of the other, as your pix show) and I did not get them correct the first time, and it popped out of gear when backing up. I put the heavier reverse spring into one of the forward gear spring holes. When originally assembled the springs were paint coded with different colors, but that only helps if (a) the paint is still there 35+ years later and (b) if you can find a reference to tell you which color goes in which hole!

To judge the diff bearings, I would think we would need to see the outer races, too.

Hopefully some of our more experienced trans folks can chime in with better analysis.
 

myronx19

True Classic
I have quite a few transmissions apart in my garage - many of the bushings have what look like "high spots". Interestingly, my friend's X1/9 makes a really loud whining noise when accelerating in 2nd gear, and only 2nd gear - it almost sounds straight cut! (this happened to him after a rebuild)

I would check the order of installation for the bushings to make sure everything lines up. Did you check for differential bearing preload and make sure it's within spec?

As mentioned by Dan - the detent springs wouldn't cause this.
 

Steve Hoelscher

True Classic
A few comments:

1: The diff bearing rollers typically don't show wear before the outer races. Check the outer races first.

2: As Dan noted, the sleeves don't spin on the shaft. They are locked in position from the preload of the 30mm nut on the end of the shaft. If the sleeve spins, its because either the nut was loose of the gear seized on the sleeve. Either way, the sleeve and the anything it touches is now ruined.

3: Mic the bore of the gear and its sleeve. Note the tolerance.

4: Diagnosing such things require knowledge of the various torque paths through the transmission to understand what is being loaded and what isn't. If the noise is heard when 3rd gear is engaged but you have not yet applied the throttle, 3rd gear is locked to the pinion (lay/output) shaft and therefore the sleeve couldn't be causing the noise as the gear isn't spinning on its sleeve, its turning the shaft through the slider and drive hub.

To make an accurate diagnosis I would like to know the very specific details of when the noise is herd. Clutch engaged or not, in gear or in the process of selecting the gear. Speed dependent? I assume this doesn't happen when selecting 4th?
 

CnC79X19

True Classic
A few comments:

1: The diff bearing rollers typically don't show wear before the outer races. Check the outer races first.

2: As Dan noted, the sleeves don't spin on the shaft. They are locked in position from the preload of the 30mm nut on the end of the shaft. If the sleeve spins, its because either the nut was loose of the gear seized on the sleeve. Either way, the sleeve and the anything it touches is now ruined.

3: Mic the bore of the gear and its sleeve. Note the tolerance.

4: Diagnosing such things require knowledge of the various torque paths through the transmission to understand what is being loaded and what isn't. If the noise is heard when 3rd gear is engaged but you have not yet applied the throttle, 3rd gear is locked to the pinion (lay/output) shaft and therefore the sleeve couldn't be causing the noise as the gear isn't spinning on its sleeve, its turning the shaft through the slider and drive hub.

To make an accurate diagnosis I would like to know the very specific details of when the noise is herd. Clutch engaged or not, in gear or in the process of selecting the gear. Speed dependent? I assume this doesn't happen when selecting 4th?
Impressive Steve. You sound like my dad (a transmission mechanic) asking a customer what "exactly" was happening at what point.
 

Steve Hoelscher

True Classic
Impressive Steve. You sound like my dad (a transmission mechanic) asking a customer what "exactly" was happening at what point.
Thanks. A good rebuilder will understand a "torque path". You're dad sounds like a good one. There are a lot of rebuilders that have no knowledge of theory at all. They are literally just parts changers.

I should note that some years ago I owned an Aamco Transmission center. Two actually. I trained many of my technicians. Also, I would assume I have built more X1/9 transmissions that anybody else, ever.
 

CnC79X19

True Classic
Your experience certainly shows Steve. I only wish I would have paid more attention to what dad was constantly trying to show me while he was still around
 
Thanks guys. I appreciate your assistance with this especially Steve H for sharing your abundant knowledge and experience.

Dan, Its not popping out of gear but I will change the spring. Myron, I'm certain the gears and bushings are stacked properly. The 30mm nuts were locked with an impact and all line up.
The diff preload does concern me as on the previous teardown/reassembly I had difficulty calculating it as the carrier is warped. I did take it to a trans shop fully assembled to check who added a few shims and said it was okay.

Steve, There is no noise in any other gear except 3rd. I press the clutch pedal down and 3rd gear is selected without any noise. If the clutch pedal stays depressed there is no noise. Upon releasing the clutch pedal, the whirring noise occurs when the clutch bites and stays until I apply the throttle. When I apply the throttle, the noise goes away and If I then release the throttle the noise is no longer heard. The noise only occurs immediately after the clutch pedal is first released. When on/off the throttle in 3rd in normal driving the noise does not occur. The noise is also evident when downshifting from 4th to 3rd whilst engine braking and disappears as the engine slows but will go away when throttle is pressed.

I measured and remeasured the clearances several times using a cheap vernier caliper and this is what I got. Logic would dictate that the ID of the bush would be larger than the OD of the pinion but these are the measurements I got. I don't know how helpful this will be.
pinion OD 30.82 mm,
old 3rd bush ID 30.64 mm,
new bush ID 30.67 mm,
gear ID 39.8 mm

I have attached some photos of the diff races. The other thing that I noticed is that the input shaft smaller bearing has a sloppy fit and i intend changing it. The inner part fits very loosely and moves on the end of the input shaft.

Thanks
Peter
 

Attachments

Yes, I had a feeling the diff bearings might be bad and I've got a set ready to go on. I kind of discounted this as being the cause of my noise as it only happens in 3rd gear but I probably may be wrong. Does anyone know the best way of removing the races. Can a tool be fabricated?
 

Steve Hoelscher

True Classic
Peter, per the clearances of the gear and sleeve; we don't care about the ID of the sleeve, we need the sleeve's OD and the gear's ID. The difference is its clearance. The caliper is better than nothing, although you can buy a cheap mic that will do the job. I wouldn't use it for building racing engines but figuring clearances for the gears is fine.

As Dan noted, the diff bearings are junk. Those outer races are ruined and typical of what I see. The rollers appear OK but the races have broken down, usually from contamination or improper clearances.

I think I have identified your problem. Please post detailed photos of the primary teeth of 3rd gear. Both the input shaft and layshaft gear. If I am right, that will show the problem.
 
Last edited:
Thanks again Steve. I've measured the OD of the hubs.
Old 39.80
new 39.84
gear ID 39.89
I've attached the photos as requested. I've only got an old iphone camera available at the moment.
I'm excited to get a solution to this.
Cheers
Peter
 

Attachments

I'm in the process of changing the diff bearings. Can anyone share their method of removing the race from the blind hole. I've searched the archives and there is mention of a puller and heating the unit in an oven. I've seen videos on youtube where people weld a bead inside the race causing it to shrink and come out.
 

Dan Sarandrea (Phila)

Waitin' On Parts...
IIRC on mine, once the seal is out, there is a tiny bit of the race that you can put a drift on from the outside-in. Lots and lots of gentle taps later, the race is coaxed from the case casting.
 
Thanks Dan. By the looks of this photo someones been in here before and did exactly that. I was wondering how that gouge may have occurred. Its good to know that you were successful doing it this way. Sometimes I overthink things. I will give it a go.
Cheers
Peter
 

Attachments

Dan Sarandrea (Phila)

Waitin' On Parts...
Thanks Dan. By the looks of this photo someones been in here before and did exactly that. I was wondering how that gouge may have occurred. Its good to know that you were successful doing it this way. Sometimes I overthink things. I will give it a go.
Cheers
Peter
Am I wrong thinking there might be reliefs in the casting under the bearing race with the intent of giving an internal jaw puller a place to put the jaws?
 
Many thanks Dan and Bjorn. The diff bearings and races are out. You are correct in that once the seal is out there is space in the relief to tap on the race with a punch to remove.
The new bearings are in. The old race was seated a couple of mm above the casting of the case. Should I install the new one to the same position or should it sit flush with the case?

I'm hoping that Steve H can find the time to look over my 3rd gear photos and offer his expert advice. I greatly appreciate his support and advice working through this issue.

Regards
Peter
 

Attachments

Top