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Vin's S4 Transmission Rebuild for Dummies

56K views 186 replies 21 participants last post by  AlessandroM 
#1 · (Edited)
Hello All,

1991 Spider with about 98K miles.

Firstly, I want to thank all of those before me who have posted threads on our transmissions. I did a ton of reading and learned a lot from you. Thank you.

Special thanks to Papajam, who walked me through this over several calls. He always takes my calls and never makes me feel foolish for asking all those newbie questions. A true Mentor in every sense of the word.

Honorable mention goes to Alfar7, Gordon Raymond, ARwrench, racingswim2006, who all helped me on several other threads I posted during the build and mcola who visited during the build and caught a bad throw out bearing for me. If I missed anyone, thank you.

During my preparation for the rebuild, I could find quite a few threads on transmissions rebuilds but I couldnt find a complete thread on dissassembly AND assembly. As of tonight, I am at the point of re-sealing the cases, so no excuses from me.

I am writing this thread from my perspective, the ultimate "dummies series user". I'm no mechanic but can follow instructions pretty well. This means tons and tons of pictures.

The thread is meant for the novice like me, so the experienced people in the group may find it a bit much. Fair warning.

My motivation was the start of 2nd and 3rd gear grind.

My plans going in was:

Apply the 1st Gear fix found on the AlfaBB
All new syncro rings
All new syncro sleeves
Dog gear replacement on 1st, 2nd and 3rd
And of course whatever Alfa surprises await :grin2:

Like I said, there are a lot of pictures, so be patient with me as I post.

So..........lets start!!!!!!!!!!!!!
 
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#27 ·
Olive up, place the gear puller under 2nd gear.
Machine Tire Machine tool

Gear Auto part Transmission part Hardware accessory Differential


2nd Gear pull
Gear Auto part Rotor Hardware accessory Bicycle part


2/1 syncro hub
Auto part Bearing Ball bearing Bicycle part Hardware accessory
 
#29 ·
2/1 syncro ring
Auto part Gear Clutch part Hardware accessory Rim


2nd gear
Auto part Gear Hardware accessory Nut Axle part


To remove 3rd gear, place in bench vise to remove small snap ring
Auto part Machine Gear

Auto part Machine Metal Transmission part
 
#30 ·
Input shaft up, place the gear puller under 3rd gear.
Auto part Tool accessory Gear Machine tool Machine


3rd gear pull
Auto part Hardware accessory Gear Bicycle part

Auto part Hardware accessory


4/3 syncro hub and 3rd gear
Auto part Hardware accessory
 
#31 · (Edited)
Note that there are 4 small Woodruff keys. 2 shown here and 2 on the opposite side. They are used to align the syncro hubs later on.
Metal Pipe Muffler Auto part


Be careful as they easily fall out.
Geological phenomenon Water Sky Event Tree


Well, that is all of the parts off the shaft!!!!!!!!!

Disassembly done!

Nice!
 
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#37 ·
Inspection time!

Hello All,

Thanks for the kind words.

Ok, inspection time.

For the shift forks, you want to inspect the areas that ride on or touch the sides of the syncro sleeves. Basically looking for wear. There is a measurement that will be taken but that is together with the syncro sleeves a bit later. For my forks, the 1/2 and 3/4 were fine. The 5th/reverse had some issues though.

Here is the 5th/reverse that shows signs of burning and burs on the end that controls the reverse idler gear. Need a new fork here.
Auto part


Luckily, this fork is for sale new, reproduction.
Metal

Font Horseshoes Games Metal

Font Metal
 
#38 ·
Syncro Sleeves (Sliders)

Here are all the syncro sleeves (some call them sliders) in car position. Left to Right, 4/3 2/1 R/5.
Tire Wheel Auto part Automotive tire Rim


We are looking for signs of wear in the groove (gap measurement coming up with forks) but more importantly, looking for wear on the inside. Here is the 2nd gear side. You can see that the tips are not sharp, but more blunt. This is the part that mates up with the dog teeth on the gears and these two parts are the grinding that you hear. If your dog teeth are worn, so should the corresponding syncro sleeve teeth.


If your sleeves have never been changed, you can see what they looked like leaving the factory, even today. Since there is no syncro for reverse, the reverse side of the R/5 syncro sleeve has never been used. Here you can see the top was the reverse side. Nice and sharp! So nice!

If you want, you re use this sleeve by just turning it around since it was never used. I chose to use a new one as I didnt want any gap issues with the new fork.
Tire Automotive tire


Here is a picture of the new syncro sleeves. They are not as sharp as the original, but others have confirmed that they work well.
 
#39 ·
I would think about getting another bellhousing. The sleeve that the throw out bearing slides on should not come out. You should not be able to pull it out by hand at all.
 
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#40 ·
Syncro Rings

Here are the syncro rings, again in car position. You are looking for wear. These should be rough to the touch like sandpaper. You can see that on mine, each one has shiny sections where it is smooth. Some even have grooves in them from the dog teeth

This is an easy decision, change them all!
Auto part Metal


Here is the 2nd gear dog teeth and corresponding syncro ring
Tire Auto part Automotive tire


And the groove in the syncro ring left by the dog teeth
Auto part Zipper Metal
 
#41 ·
Dog teeth gears

These are the big issue when it comes to grinding. You are looking for sharp teeth that will engage with the syncro sleeves. The more blunt, the more grinding.

Again, thanks to jcslocum for these clear examples of what to look for. Here we see blunt and sometimes even missing teeth.
Text Font


Here is 5th, where there is little wear. Nice and sharp
Product Metal Auto part Bearing Steel


Here is my 2nd gear, where we can see the blunt tips and burrs forming on the edges.
Gear Auto part
 
#42 ·
Gears

As for the gears themselves, you are looking for broken or chipped or missing pieces, signs of great wear. You must inspect the gears on both the mainshaft and layshaft.

Here is a picture of one of the gears. The dog teeth are pressed on, but you can see the helical cut gear.
Gear Rotor Hardware accessory Auto part Metalworking


All of my gears, 1 through 5 were good, however the reverse showed some issues.

The teeth were not sharp and were blunt, especially on the idler. When looking at the reverse gear on the mainshaft and on the layshaft they too showed signs of wear. The transmission was not jumping out of reverse (a sign of worn teeth on the gears) but it was certainly well on its way.

Idler
Metal Auto part Brass Gear Hardware accessory


Mainshaft gear
Finger Metal Gear Ring Auto part


Layshaft gear
Auto part Cylinder Pipe
 
#43 ·
It was recommended to replace all 3 parts as a set so I contacted a local retired Alfa shop and he had a used set. They aren't new, but they are better than what I had and were a reasonable cost. I will pay special attention to touch another gear before I put it in reverse to avoid this from happening again.

Here is the used idler on the right and the original on the left. Not new, but better.
Gear Auto part Metal Hardware accessory Transmission part


Replacement Mainshaft gear
Gear Auto part Hardware accessory Nut Metal


Replacement layshaft gear
Auto part Metal Cylinder Wheel
 
#44 · (Edited)
Replacing Dog Teeth Gear

For all of the dog teeth gears that are worn, you will need to replace them. If you are lucky enough to have donor transmissions, these can be had from 4th and 5th gears as they are typically in great shape, being tall and sharp teeth. Centerline do have some beautiful brand new ones but a bit pricey for me. I ended up getting mine from APE (as well as a set of internals for the 1st Gear Fix coming up).

2nd Gear to start
Auto part Bearing Clutch Hardware accessory Transmission part


Remove snap ring as described before
Bearing Auto part Ball bearing Transmission part Hardware accessory


Remove the outer syncro ring, 2 quadrants, and 2 check straps. Put them in a baggie for later.
Note that the cut out of the dog teeth gear is directly in front of one of those, what I believe to be, oil galleys. Important to remember for re installing.
Auto part Bearing Wheel


I used the snap ring to press the gear out of the dog teeth. To re install the snap ring (you will get a lot of practice removing and replacing these large rings), start by installing the end with the ear into the cutout of the gear and feed into the groove found on the dog teeth.
Auto part Bearing Rotor Ball bearing Wheel
 
#45 ·
Using the snap ring pliers, cover with your hand just in case, start to open the ring by pushing the ear into the cutout and work the snap ring around the groove until it is fully seated all the way around.
Bearing Ball bearing Auto part Hardware accessory


Here is the snap ring installed on the gear without all of the syncro guts underneath.
Auto part Gear Rotor Hardware accessory Wheel


Back to the shop press. Place the 3" gear puller under the snap ring.
Auto part Steel


Using the 1 1/4" socket to press the gear out is a perfect size
Auto part
 
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#46 ·
Took some pressure and came off with a SNAP, but off it came. Here you can see that the inside of the dog teeth is keyed as well as the top of the gear.
Auto part Clutch Differential Gear Rotor


Gear and dog teeth separated. I will show how to install the "new" dog teeth next when we do the 1st Gear Fix.
Gear Auto part Hardware accessory Rotor Axle part
 
#47 ·
#48 · (Edited)
I am using this transmission assembly lube to help with the assembly.
Material property Circle Label


Put a bit of lube on the gear. I bought a paint brush later. :)
Auto part Rotor Gear Metalworking


Put a bit of lube on the dog teeth ring
Gear Auto part Wheel Clutch Tire


Align the dog teeth on the gear so that the cut out lines up with or as close to the oil galley on the gear. Both can be seen here, 12 O'clock.
Auto part Bearing Clutch part Ball bearing Wheel
 
#49 ·
Over on the shop press use an appropriate plate that will cover the top of the dog teeth ring.
Tool accessory Gear


Voila! Newly pressed dog teeth on 1st Gear
Gear Rotor Hardware accessory Auto part Metalworking


Place NEW syncro ring on so that the cut out of the syncro ring (seen at 6 o'clock) is directly opposite the cut out of the dog teeth gear (seen at 12 O'clock).
Clutch part Auto part Gear Bearing Wheel


Assemble the small quadrant so that it points into the dog teeth ring and the large quadrant points out of the syncro ring. Oh yeah, don't forget the 2 check straps.
Clutch part Auto part Bearing Wheel Clutch
 
#51 · (Edited)
Remove and replace all of the the dog teeth rings as you need.

Replace all of the syncro rings (we just did 1st gear) and re assemble gear assemblies.

2nd gear replaced dog teeth and syncro ring replaced.
Auto part


3rd gear replaced dog teeth and syncro ring replaced. No picture :surprise:!

4th gear will need to back into the bench vise to do all the work.
Auto part Bearing Rotor Gear Clutch


4th gear syncro ring replaced
Auto part Automotive engine part


5th gear syncro replaced
Auto part Font
 
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