No 4th syncro; transmission tear down

[wizard124]

I bought the car knowing 4th gear syncro was no good. I began the tear down yesterday. Previously, I bought (on Ebay) a Fiat repair manual for the 5 speed transmission; also have the Brooklands manual. I hope this is helpful to others who may have to go down this path
Scrubbed, brushed and de-greased the tranny:


Removed the bellhousing, yoke, and shift tower:


Removed the bottom plate to find this:


Removed the 5th/reverse housing:


Shift levers pulled:


Removing speedo gear, 5th/reverse gear and idler gear:


Looking at countershaft. Remove 2 bearing at either end to remove countershaft:


Pull out the 2 shift forks (previously unbolted from their shift rods). Remove 3 machine screws holding the mainshaft bearing retainer. The input shaft, pull forward to remove. The mainshaft pulls out from inside the housing once its bearing is removed from the shaft and housing.:


The 4th gear syncro is on the end of the input shaft. I found mine mine missing its teeth. Obviously the reason 4th gear was grinding and the source of the ground brass in the pan:


Also, there was not a syncro spring for 4th gear The Fiat manual doesn't show one but the Brooklands does Can someone confirm there needs to be one (I assume this is why mine self destructed). This transmission was worked on once before ( the retainer screws were burnished) and the spring omitted.

[So Cal Mark]

that may be the worst synchro I've seen

[BEEK]

there was a spring, it is now all that metalic substance you found in the pan. i have seen syncros do exactly what you are seeing, unfortunately you will probably need a new 4th gear and defiantly a shift sleeve, syncro and spring

[wizard124]

there was a spring, it is now all that metalic substance you found in the pan. i have seen syncros do exactly what you are seeing, unfortunately you will probably need a new 4th gear and defiantly a shift sleeve, syncro and spring

Thanks Beek!
I'll add a spring to the parts order.

Another question There are 2 shift sleeves. One of mine has a small groove running around the exterior circumference (see picture above), the other does not. Are they interchangeable? I have a couple of NOS sleeves, both without this groove. Can I use them as replacements?

I have started to clean up and re-assemble the input and main shafts. I am very lucky to find in my spare parts, new bearings (input and main), 2 shift sleeves, new syncro rings, and 2 new shift forks, and a couple of bearings I haven't matched up yet. 4th gear looks pretty good to me. I'll post a picture for your opinion tomorrow.

I appreciate your input

[BEEK]

yes the sleeves are the same, post the teeth end, where the hub engages the gear. those should be pointed, not rounded

[BEEK]

these are the mating side on the sleeve

[wizard124]

Beek, good call. The teeth on the 4th gear side are pretty beat up.


Found damage and scoring to this bearing also:

[BEEK]

how do the teeth on 4th gear look?

[wizard124]

how do the teeth on 4th gear look?

4th gear still has pointy teeth. Not perfect but not bad like the sliding sleeve's. Parts should arrive tomorrow. I'll be putting it back together soon. Every part has been cleaned and covered ready to be re-assembled.

[bradartigue]

I'd spend a good deal of time - and high pressure air or carburetor cleaner or both - and blast off all of the oil fluid and gunk and get everything clean and dry, then re-oil it all. It may be a trick of the camera flash but those innards appear to have lots of tiny scratches and grooves, you have some tiny abrasive things dancing around in there.

[wizard124]

I'd spend a good deal of time - and high pressure air or carburetor cleaner or both - and blast off all of the oil fluid and gunk and get everything clean and dry, then re-oil it all. It may be a trick of the camera flash but those innards appear to have lots of tiny scratches and grooves, you have some tiny abrasive things dancing around in there.

I've wiped, brushed with diesel, flushed out, wiped again, electronics cleaner thru the bearings, dried, air blasted to get all the parts as clean as possible.

I'm in the re-assembly phase. Lubing the pieces with Red Line MTL as I go. The Fiat factory manual is priceless with good exploded views and step-by-step instructions. I re-painted the bottom plate this afternoon. It should be buttoned up tomorrow

[wizard124]

I was just about to bolt on the bell housing and add some tranny fluid........

I decided to review the Brooklands book when a big Oh S__T caught my eye In it, it refers to the proper orientation of the 1/2 and 3/4 shift hubs. Specifically, it specifies the direction the notched side( of the 3 lugs) of each hub should point. The 3/4 has the notches towards 3rd gear and the 1/2 has the notches pointing towards 2nd gear (assuming I am understanding it properly).


Since I never noticed the distinction in the hubs and the Fiat factory manual doesn't says anything about this, I need some advice as to if this is important or not. I have assembled the shift lever. The shift feels good through all gears. The 1 and 3 throw distances are the same as are the 2 and 4 throws. The input and output shafts show no binding. I removed the inspection plate gears and cycled through 1 to 4 and can not see any discernable differences. By visual inspection, one can't tell the notch orientation. Am I making sense

I am thinking this is not a functionality issue. Maybe for lubrication? These notches run around the circumference which doesn't seem like it helps lubricate the shaft/gear interface. And when the gear is engaged there is no relative movement between the gear and hub.

LOOKING FOR ANSWERS If this is a big deal, I have a lot of work to do

[bradartigue]

I'd spend a good deal of time - and high pressure air or carburetor cleaner or both - and blast off all of the oil fluid and gunk and get everything clean and dry, then re-oil it all. It may be a trick of the camera flash but those innards appear to have lots of tiny scratches and grooves, you have some tiny abrasive things dancing around in there.

I've wiped, brushed with diesel, flushed out, wiped again, electronics cleaner thru the bearings, dried, air blasted to get all the parts as clean as possible.

I'm in the re-assembly phase. Lubing the pieces with Red Line MTL as I go. The Fiat factory manual is priceless with good exploded views and step-by-step instructions. I re-painted the bottom plate this afternoon. It should be buttoned up tomorrow

Using Redline in a newly rebuilt transmission? I wouldn't use that scratchy stuff once running. Are people still using that or are you just using it for assembly?

[wizard124]

Using some left over MTL for assembly. I am planning on running with Redline MT90.

[wizard124]

I spoke with 2 well repected authorities. Both told me that the orientation of the hubs is not important

I finished the transmission re-assembly this afternoon and filled it with RedLine MT90. It will be awhile before it and the engine are put back into the car as I still intend to paint the engine compartment.

For any members with the desire to repair their 5 speeds, here are my helpful hints:
1) Obtain a Fiat factory manual and/or detailed exploded diagrams. The diagrams detail the intricate parts such as detent dowels, shift pins, springs, individual ball bearings, etc. Also, it shows the order of parts on the shafts. As a note, this Fiat manual was incorrect in 2 ways. First, it did not detail the syncro spring for 4th gear. It also showed a washer and retainer clip for the needle bearing that fits inside the end of the input shaft. These 2 parts aren't to be found on my transmission.
2) The Brooklands manual is OK. I found it harder to follow; with pictures that aren't very big nor very clear. In any case, I would not want to attempt this without some reference.
3) Take many digital pictures and work slowly. Follow the order outlined in the manuals. I know its difficult for men to follow instructions
4) Have a large work table so that you can lay out the order of parts as they are dis-assembled. Bag and sharpie bolts, spacers, bearings, etc in logical groupings. Clean, breakdown, repair, and re-assemble sub-groups one at a time to avoid mistakes and confusion.
5) Did I already say slow and deliberate!
6) Tools I recommend: 1/2 inch drive impact driver, quality ring pliers, work light, small puller (for small spacer at end of output shaft, the yoke came off by tapping with a hammer), punches (for removing bearing races).
7) soft paintbrush, solvent, and tub large enough to clean and flush out cases, gears, and bearings.
check for shafts free to rotate, connect the shifter and make sure it can select all speeds and reverse

Go for it