Third gear grind is back

I have been asked about modifying the 3-4-5 sychros to a blocker ring type to replace the OE Porsche Type. This is not small project as I have actually investigated this previously. Make such a change would require designing a new slider hub that can accommodate the blocker ring type synchros, a new slider for the new hub and blocker ring synchros and then redesigning the gear.

For the gear, the engagement ring is pressed onto a splined hub that is part of the main gear. That hub could be pressed off and a new blocker ring type hub machined and pressed on.

CAD design tools and CNC machining makes this a much more feasible project now. That said the cost of design work alone is probably $25K. CNC Machined parts $250+ each for the slider and hub and also for the blocker ring hub. Then you would have to find a blocker ring that of appropriate size. It would actually be easier to find a shop that could reproduce the OE parts with greater quality. Or, develop a kit to adapt and alternate transmission. The Toyota C52 from the MR2 comes to mind. It has similar ratios and packaging.
 
So, Steve,

When I'm going to need a transmission rebuild, it might be less expensive to go to a full K20 swap...:D

It start to make sense to buy an old rusty Fiat for $3000 if it got a good tranny!
 
There are two expander bands inside the Porsche syncro. Check the condition of these bands. If they are worn, they will not aid in expanding the Porsche syncro band properly reducing the amount of friction the outer syncro band can produce to help speed match the gear to slider prior to making the gear shift transition. Other item to check is the two blocks associated with the expander band. If these are worn or have a problem this will also impede the ability of the expander bands to do their job.

The inverted Borg Warner syncro used on 1st-2nd gear can develop problems if the grooved tapered cone on the gear is worn or if the syncro ring is not Fiat per ID spec. ID slider detents and pressed steel detent caps can wear too, check this as there is more to 1st-2nd syncro than just the syncro rings.

Bernice

Thanks for your replay Bernice.

The expander bands look okay to me. Here are pictures of the bands from third gear:

001.JPG
002.JPG


I have no idea why one has an "O" stamped into it.

The original synchro rings have grooves machined into the inside surface. I have no idea why Fiat did this, but I have noticed that neither of the two after market synchros have these grooves.

Aftermarket:

004.JPG


Stock Fiat part:
005.JPG


Brian
 
I have been asked about modifying the 3-4-5 sychros
Steve, almost seems more feasible to look at other possibilities. Perhaps something like adapting all of the internals from a more modern trans, or adapting a newer design Fiat trans to the X, or anything along similar lines. Rather than try to "bandage" the old design.
Otherwise Daniel is right, it will be better (and perhaps less costly in the end) to just do a complete engine/trans swap. Expensive yes, but lots of advantages. And ultimately if the X's trans becomes not worth repairing (parts, cost, etc), then any option will be costly.
 
I have been looking for a third/fourth slide for my '83 X1/9. I am finding a lot of different part numbers for what seems to be the same part:

4092083
4366610
7629652
7581748

What is the correct part number?

Brian
 
Brian, I don't know about this particular part. But in general there are frequently many Fiat part numbers for the same part. I believe it is due to superseded numbers, various model applications, crossover part fitments, etc. Basically meaning any of them can be good numbers. Usually it seems the highest (numerically) part number is the latest. But often I find a part listed under another of the numbers. And I might find the part under any one of the numbers but not the others, despite being the same part (has to do with how the seller lists it). So I usually look for all of the part numbers that apply.
 
I ordered synchros and 3rd/4th slider from Italy through ebay from a seller that goes by the name of lineav. He has thousands of car parts listed (Fiat and others).

I'm still looking for a 3rd/4th shift fork.

Brian
 
I have been looking for a third/fourth slide for my '83 X1/9. I am finding a lot of different part numbers for what seems to be the same part:

4092083
4366610
7629652
7581748

What is the correct part number?

Brian

Brian, it maybe because all x19 5 speed aren't sharing the same parts. There were some changes over the years.
 
Brian, it maybe because all x19 5 speed aren't sharing the same parts. There were some changes over the years.

Thanks Daniel and Jeff. I checked some part suppliers and found that many part numbers were superseded several times, for essentially the same part. I am not sure of the reason, but there may have been small improvements in materials, dimensions, processing, etc. From my experience in manufacturing, often a part will change number if any part of the process changes. In this way, if things go wrong and the part begins to experience failures, it can be identified by the part number, when the failures started to occur and a recall can be initiated. For example, if a heat treatment change occurred and the part number was changed from 1111 to 2222 at that time, if failures start occurring you will know that part number 2222 is faulty. Of course, this is just a guess on my part.

Brian
 
Hello Brian,

Replace the syncro expander bands, they are worn. Beyond the wear spot around the top of the arch, these change shape as they wear. The initial curve they are made with flattens over shift cycles and reduces their effectiveness at producing friction on the inside of the Porsche syncro.

The small grooves on the inside of the OEM Fiat Porsche syncro is to provide space for the oil to exit (think tire treads and water dispersion) as the band is pressed against the inside of the Porsche syncro. This is another inside friction aid to help match speed of the oily parts involved.

Use OEM Fiat parts if at all possible.

It should be understood Fiat made constant changes and improvements to this transaxle during it's production life. While there are many parts that can be interchanged, make absolute sure not to mix older version parts in a newer transaxle. In some cases, the parts will not fit at all (key way driven 5th gear on early versions -vs- splined 5th gear on later versions. This was done due to ripping out of the key way when least expected. This is just one example).


Bernice




Thanks for your replay Bernice.

The expander bands look okay to me. Here are pictures of the bands from third gear:

The original synchro rings have grooves machined into the inside surface. I have no idea why Fiat did this, but I have noticed that neither of the two after market synchros have these grooves.


Brian
 
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On another issue, I have a noticeable whine from the gearbox in fifth gear and I only hear it under load (it goes away when I lift off the throttle). It is not really loud, but only occurs in fifth. Is this "par for the course" in the X1/9 transaxle?

Brian
 
That description sounds typical of a bad bearing. But I don't any specific info on these trans in particular.
 
That description sounds typical of a bad bearing. But I don't any specific info on these trans in particular.

That was my thought as well, however I replaced all the bearings and the whine is still there. It's not particularly loud, but once again, it is only in fifth. I was wondering if it was due to worn gears. When I bought the car it had an aftermarket cruise control that led me to believe the car was used on highways a lot, perhaps causing more than average wear on the fifth gear components. I will inspect the gears a little more closely to see if there are any signs of wear, but I am still curious if anyone else has a noticeably whine in fifth.

Brian
 
noticeable whine

Depends on how noticeable! - yes, I have whine but I consider it to be within normal. There is little sound deadening between you and the gearbox. Check your fluid level, and perhaps there is inadequate fluid getting to the 5th gear extension? (I can't recall how the fluid is brought over there). Hmm.. How noticeable is noticeable? Brian, you're more than welcome to come and hear mine :) but I bet yours is normal.
 
Depends on how noticeable! - yes, I have whine but I consider it to be within normal. There is little sound deadening between you and the gearbox. Check your fluid level, and perhaps there is inadequate fluid getting to the 5th gear extension? (I can't recall how the fluid is brought over there). Hmm.. How noticeable is noticeable? Brian, you're more than welcome to come and hear mine :) but I bet yours is normal.

Thanks for your reply Myron. If your transaxle whines, than I suspect that mine is normal. I don't consider it objectionable, but if nobody else noticed a whine than I would have considered it abnormal and investigated further.

Regards,

Brian
 
A whine, only in one gear, isn't normal. 5th gear has the finest tooth pitch so it should make the least noise. Could easily be a bearing. Could also be improperly stacked.

The more frequent cause of a 5th gear whine is the gear/sleeve is worn out. This causes the gear to miss-align by a few thousandths and the result is whine and excessive wear on the teeth. Ultimately, the teeth will begin to fail and you'll strip the gear.
 
A whine, only in one gear, isn't normal. 5th gear has the finest tooth pitch so it should make the least noise. Could easily be a bearing. Could also be improperly stacked.

The more frequent cause of a 5th gear whine is the gear/sleeve is worn out. This causes the gear to miss-align by a few thousandths and the result is whine and excessive wear on the teeth. Ultimately, the teeth will begin to fail and you'll strip the gear.

Good call Steve. I checked fifth gear and there is definitely more play between the gear and sleeve than there is on fourth gear. Trial fitting the fourth gear sleeve into fifth improves the clearance, but not 100%. Feeler gauges indicate .005" for fifth and .002" for fourth. The service manual specifies .001" - .003". It looks like both the fifth gear and sleeve are worn.

When I get this transmission finished there won't be too many parts I have't replaced, and some twice!

Brian
 
How was a feeler gauge used to check bearing clearance?
If the feeler gauge was inserted between the gear-bearing this will NOT be an accurate measurement in any way due to the bend angle of the feeler gauge blade and gaps involved. This will skew this measurement resulting in poor accuracy.

-This method sort of works for piston to bore measurement due to the much larger diameters involved.

The only way to do this measurement,

*For OD, use a known accurate micrometer.

*For the ID, use a known accurate internal micrometer (the three legged ones aka Intramik is best).

And the measurement must be taken at several locations of the circle inside and outside to check for out of round. Once the measurements are take, bearing clearance is the difference between OD-ID.

There are two sets of sleeve bearing clearances involved. First is the clearance between sleeve bearing to gear ID which is spec in the Fiat service manual. Second is the clearance between sleeve bearing and shaft. This clearance MUST be tight, less than 0.001" to slight press fit. If the clearance between sleeve bearing to shaft is excessive, the sleeve bearing will spin on the shaft increasing slop in the gear teeth and wear.

Gear lash on 5th gear can be checked after the gear box is assembled using a test indicator or dial indicator with the appropriate tip at the gear teeth with one shaft fixed and the other shaft rocked forward-back.

Helical gears produce slide loading as they rotate with torque applied. This effectively takes up the gap between gear teeth reducing gear noise. If the gap is excessive, the gear teeth will be over loaded beyond their designed force capability and fail. There were several versions of 5th gear (key-slot drive, splined and different ratios) used in this gear box. If the gears are replaced, replace both gears as they will get happy together and will not like being interchanged.

Gear boxes are high precision devices and often not appreciated the precision and accuracy required for them to function properly. While there are tolerances and allowances designed in and built into a gear box, going too far out of these limits will cause minor to serious problems to fatal failure of the gear box.


Bernice

Feeler gauges indicate .005" for fifth and .002" for fourth. The service manual specifies .001" - .003". It looks like both the fifth gear and sleeve are worn.

When I get this transmission finished there won't be too many parts I have't replaced, and some twice!

Brian
 
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Good call Steve. I checked fifth gear and there is definitely more play between the gear and sleeve than there is on fourth gear. Trial fitting the fourth gear sleeve into fifth improves the clearance, but not 100%. Feeler gauges indicate .005" for fifth and .002" for fourth. The service manual specifies .001" - .003". It looks like both the fifth gear and sleeve are worn.

When I get this transmission finished there won't be too many parts I have't replaced, and some twice!

Brian

As I suspected.

I often get asked; "it crunches going into 3rd. How much to fix that?". I used to reply; "it probably needs a 3rd gear synchro and slider. Maybe the gear too. That's likely $XXX in parts and then $XXX in labor". Then I get into it and find that 4th isn't much better. 5th is heavily worn as yours is. The 1st and 2nd gear synchro hubs are severely worn and won't last much longer. Reverse has chewed through 75% of its service life and the diff bearings are on the way out.

So the owner only noticed the 3rd gear crunch. Yes, I could fix that but then the other failures wouldn't be far behind. Thus "fixing" specific problems is false economy. There is no way to predict what I might find other than what I typically see but that is assumption at best. Then there is the whole issue of correcting the mistakes of previous repair efforts. My now the majority of these transmissions have had somebody go into them and seldom do I find previous work to be competent.

Now we add the problem of sourcing serviceable parts to the list. Your experience is typical.
 
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