My First Transmission Rebuild (Photo Heavy)

[19-VW-74]

So, I've had my '74 Beetle for about 15 years now, and most of that time it has been under the knife, or in long-term storage. Since I registered it and made it "road-worthy" in 2013, I have only put about 3500 miles on it - because I went to college, got married, etc. and didn't have time to work out the kinks. It mostly just sat in storage.

See my original build thread here: https://www.thesamba.com/vw/forum/viewtopic.php?t=492617

Fast forward to this January, and I am finally able to work out the kinks now that I've settled down somewhat and have the time/money to do it.

One little issue that the car has always had is this weird buzzing vibration noise that happens when the car has a cold start during the colder months. While the engine is idling in neutral, the sound is somewhat consistent - and it is coming from the transmission area. This is very clear when the rear seat is removed. Once transmission is warm, or when the clutch is pushed in, or when the transmission is under load, the noise seems to go away. If I am to make this car reliable enough to drive long distances, this transmission noise needs to be addressed.

I removed the transmission from the car and started to remove the driver side diff cover to take a look inside. Note that this transmission is not original to the car - it is a dual side-cover trans, and a '74 would have had a single side-cover trans originally.

I then removed the diff from the driver side. It comes right out, but requires a firm grip on the splined shaft.

With the diff removed, I could examine the pinion gear and reverse drive gears. To my suprise, the large pinion retaining nut was only hand tight! It came off easily using just my fingers. Not a good sign.

At this point, I figured I had little to lose by tearing down the transmission further. I could have put it back together and used it as a core for a rebuilt unit, but I like a challenge. I wanted to rebuild it for the satisfaction of rebuilding it myself.

So I bought a 20-ton press from Harbor Freight and started searching for the correct tools to rebuild this thing correctly. I was able to get ahold of a set of NOS rebuild tools for the Type 1 trans from a local club member. Very cool set of tools.

So, armed with some tools, the internet, and a Bentley manual, I started disassembling the transmission further.

I removed nose cone and hockey stick from the transmission, removed all the nuts for the gear housing, and disconnected the input shaft from the main-shaft. The main shaft is disconnected by removing an external snap ring, sliding back the main shaft coupler towards the rear of the transmission, and unscrewing the input shaft from the main shaft.

At this point, I could use the lever to push the pinion shaft towards the front of the trans, and remove the whole gear housing and transmission assembly as a unit. This requires some care (a second pair of hands helps), as it is easy to drop the reverse gear when the gear housing is removed.

Here you can see the input shaft remaining inside the case, with the coupler still attached.

The next step was to disassemble the gear housing by removing the main shaft and pinion shaft, as well as the shift forks and shafts. I removed the bolts holding each of the forks to the shift shafts. I removed the reverse shaft first, then the 1/2 shaft, then the 3/4 shaft. Then all the forks can be removed. The 3/4 fork sits deep in the gear housing, so it is tricky to remove, but it can be done.

I placed the gear housing in the press, with a couple of 4x4s to support the case. I removed the main shaft snap ring and conical spring washer, then slowly pressed out the main shaft. This has to be done very carefully and helps to have a second pair of hands. Once the main shaft is free of the rear main shaft bearing, the whole assembly can fall onto the ground, so it must be supported throughout this process.

Below are the snap ring, conical washer, and thrust washer that goes between 4th gear and the main shaft bearing.

After pressing out the main shaft, the transmission quickly comes apart. It is important to keep track of the placement and orientation of the various spacers, washers, snap rings, etc.

Here you can see that the thrust washer has oiling grooves that must face 4th gear, with the blank side facing the main shaft bearing.

_________________
-Austin
My 1974 Standard Beetle Build:
http://www.thesamba.com/vw/forum/viewtopic.php?t=492617

[19-VW-74]

The main shaft comes apart quickly. At this point, 4th gear can slip right off the main shaft, along with it's needle bearing, and synchronizer ring. Then the 3/4 slider can come off as well, with no tools required. Be careful not to drop the 3 detent keys and springs. This leaves you with the 3/4 hub, 3rd gear, 3rd synchronizer, and the 4th gear inner bearing race still attached to the main shaft.

Note in the picture above that the 3/4 hub has an annular groove cut into it on the 3rd gear side. This is important for reassembly.

Now we can press the 3/4 hub and 4th gear inner race off the main shaft. I used an impact socket to press the shaft through the arbors below. I first measured the OD of the socket to be sure it would not get pressed into the parts being removed.

Now I could remove 3rd gear and the synchronizer ring.

I immediately noticed some serious wear on the stop washer for 3rd gear. This was likely caused by the pinion bearing nut being loose. With that nut loose, the pinion shaft moves forward in the transmission when it is under load. This is due to the way the pinion gear teeth push against the ring gear when the transmission is loaded. This is somewhat counteracted by the angle of the teeth on the constant mesh gears in the transmission, but not enough.

The pinion shaft was able to slide forward enough to allow the fixed 3rd gear on the pinion shaft to collide with and rub against the main shaft 3rd gear stop washer. Similar wear is visible on the pinion shaft 3rd gear.

With the main shaft now completely disassembled, I can move to the pinion shaft.

I placed the pinion shaft into the press and used a homemade tool to press 4th gear down and relieve pressure on the snap ring at the front of the shaft. The homemade tool is a harbor freight axle nut socket that I cut up and welded to use for pressing u-joints into my Subaru's prop shaft. Those $5 sockets are great for making homemade press tools.

With the snap ring removed, the small pinion bearing inner race can be removed, then 4th gear, then the large spring. Note the orientation of 4th gear. The side of the gear with the wide shoulder faces the spring. The side with the narrow shoulder faces the small pinion shaft bearing.

Next we remove the 3rd gear snap ring. This snap ring comes in different thicknesses to adjust the end play for the 1st and 2nd gears on the pinion shaft. Don't loose this snap ring. Make sure you tag and bag all your snap rings, because they are all different and some are no longer available new.

With the snap ring removed, the shaft can be further disassembled. 3rd gear slides off, then 2nd gear and needle bearing, then 2nd synchronizer, then 1/2 clutch hub and sleeve (along with detent keys and springs), then 1st gear synchronizer, then 1st gear.
_________________
-Austin
My 1974 Standard Beetle Build:
http://www.thesamba.com/vw/forum/viewtopic.php?t=492617

[RCP Phx]

Looking good so far, are you planning any gear changes? What are they currently?

[19-VW-74]

[19-VW-74]

Right about now, you'll probably notice that my pictures are looking better. I got a new phone in February and the pictures improved drastically, which should be great for posterity.

Continuing on...

With the small retaining nut removed, I can now press off the pinion bearing.

I didn't want to damage the pinion bearing upon removal by pressing on the outer race, so I tried to figure out a way to press on the outer race.

I was able to make some progress by using an old wheel bearing race from my Subaru. I believe this was the rear outer race from my '91 Legacy if any one is interested. It was the perfect OD and fit well. The only issue is the ID of the race tapered in enough to prevent the pinion gear from passing through.

However, I was able to break the pinion bearing free and push it about 1/4" using this bearing race. My next idea was to design and 3D print a special arbor to use in my press. I designed it in Solidworks and printed it in PETG at 100% infill. It was sturdy enough to allow me to fully press off the bearing.

_________________
-Austin
My 1974 Standard Beetle Build:
http://www.thesamba.com/vw/forum/viewtopic.php?t=492617

[19-VW-74]

Once I removed and cleaned the pinion bearing, I was able to inspect it for wear. The bearing turned smoothly, with little resistance, but was rather noisy once clean and dry. The outer races and rollers showed moderate wear and pitting.

This bearing is marked FAG 524810D Germany

I decided against re-using it and ordered a new FAG bearing on ebay for $110. The replacement bearing is marked 531068 and is made in Hungary.

This new bearing is different from the original in that it is has different sized roller bearings inside. The original bearing (524810D) has identical inner races. Other than this difference (which should be an upgrade), the bearing new bearing is a direct replacement.

To compare the dimensions of the 524810D and 531068 bearings, feel free to view them in my gallery.
_________________
-Austin
My 1974 Standard Beetle Build:
http://www.thesamba.com/vw/forum/viewtopic.php?t=492617

[19-VW-74]

With the pinion shaft completely bare, I was able to clean it and inspect. Surprisingly, I don't see any alarming wear.

This shaft is marked G833, which denotes that it is made by Gleason, has 8 teeth, and meshes with a ring gear with 33 teeth, for a gear ratio of 4.125:1.

Elsewhere, the shaft is engraved with an employee ID and a pinion depth deviation measurement of 0.28mm. Since I don't have access to a pinion depth tool, this is not very useful to me. What is important is that the numbers on the pinion match the numbers on the ring gear.
_________________
-Austin
My 1974 Standard Beetle Build:
http://www.thesamba.com/vw/forum/viewtopic.php?t=492617

[19-VW-74]

Next, I cleaned up and inspected the 1st gear idler, synchronizer, and bearing. The gear and bearing are in excellent condition. The synchronizers were near the wear limit in the Bentley manual.

OG synchro on the left, New Deihl synchro on the right:

OG synchro:

New synchro:

The roller bearing and inner race were also excellent:

_________________
-Austin
My 1974 Standard Beetle Build:
http://www.thesamba.com/vw/forum/viewtopic.php?t=492617

[RCP Phx]

You can make a tall "spanner" socket out of some correct size pipe with the teeth cut out and weld a socket on the end to re-torque it!

[19-VW-74]

[19-VW-74]

Next, I cleaned up and inspected the 1st/2nd gear clutch hub and slider, as well as the reverse gear teeth.

The teeth inside the slider are in excellent shape for both 1st and 2nd gear. Very little wear on the tips of the teeth as well.

Here you can see that the teeth are cut with a reverse chamfer to improve engagement with the dog when under load.

The reverse teeth are in surprisingly good shape:

The clutch hub that the 1st/2nd slider moves on is also in good condition. There is some fretting where the 1st gear shim rides, but nothing terrible.

Here I can see a bit of wear on the 2nd gear thrust surface. This is probably due to the loose small pinion nut. Nothing terrible. I will wet sand this surface before re-installing.

The teeth around the hub show virtually no wear.

_________________
-Austin
My 1974 Standard Beetle Build:
http://www.thesamba.com/vw/forum/viewtopic.php?t=492617

[Igpoe]

If I tried this I'm pretty sure I'd have parts left over after I put it together.
_________________
'73 super.

[Bruce]

[19-VW-74]

[Bruce]

Every 1st and 2nd gear idler I use gets the radial grooves added. Even those that ride against the early 1st gear thrust washer that already has two reliefs for oil.

[rugblaster]

Looks like you are having tremendous fun. I don't have a Bentley manual, but if it doesn't tell you the circlips on the end of the main and pinion shafts fit one way, it should. They fit either way, but they only go on correctly one way. Get a round punch or drill bit and place the clip over the round thing and you will see the clip is not perpendicular to the round thing. The smaller diameter goes up. Carry on.
_________________
'69 Karmy, '69 Camper, Meyers clone, '65 drag bug, 10.78 @ 128 (sold it) '51 Dodge farm truck,
'09 MB E350 '18 MB E400, '65 Plymouth Valiant convertible and a '19 Ford F250 King Ranch (nicer, but dirty, farm truck)

VWoA factory trained line tech 75 till 90 or so
ASE Master Certification
VWoA Assoc. of Quality Technicians inductee (One of 25 in the five state southwest region)
La Confrerie des Chevaliers du Tastevin (San Angelo Chapter)
TCU ......GO FROGS!!!!!!

[nsracing]

I have touched-up bearing inner race surfaces before w/ a toolpost grinder setup on a lathe. I little better than running a used set of bearings if you don't have a new one. I did these in race transmission we used in our car/.

Just make sure you can re-introduce the pinion back into the case as close as it was when you took it out.

New bearings of course is the way to go.

You also need a way to dress the galled up surfaces in the gear or the hub. You can dress that area w/ a carbide tool in a lathe or toolpost grinder.

Very nice detailed work -you got.

[19-VW-74]

It has been a long while since I updated this, but the transmission has been back together for nearly a year. I did have to take it apart again because my 3rd gear synchro was defective, causing it to grind unless I shifted into 3rd slowly. That's all sorted now.

Anyways, here's some more updates from the process.

First, I took care of 1st gear, which had some heat/galling damage on the thrust surfaces. I wet-sanded the thrust surfaces on plate of glass and then took a Dremel with a coarse sanding drum to make oil grooves. Afterwards, I polished with a little felt drum.

I've read that it's a good idea to drill the thrust surfaces of the clutch hubs for better lubrication. So I drilled three holes in each with a 3/16" HSS bit.

3/4 clutch hub:

The 1/2 clutch hub was a much harder steel and took a lot of pressure, oil, and reduced speed to drill. I'm sure a carbide bit would have made it easier, but I had some decent enough HSS bits that worked if I went slow.

One issue I discovered from using the HSS bits was that it sort of mushroomed the area around the drilled hole on the 1/2 hub. To sort this out, I took a diamond burr on my dremel and removed the extra material.

After the holes were sorted out, I cleaned everything, then lapped the gears against the thrust surfaces with valve lapping compound. A couple of applications had them spinning very smoothly.
_________________
-Austin
My 1974 Standard Beetle Build:
http://www.thesamba.com/vw/forum/viewtopic.php?t=492617

[19-VW-74]

Upon close inspection to 3rd gear on the pinion shaft, I noticed that most of the teeth had small chips taken out of them on the edge facing 4th gear. It looks like this was caused by the loose pinion bearing allowing 3rd gear on the pinion shaft to rub against the stop washer on the main shaft 3rd gear.

I took care of this with a Dremel with a very small burr.

Teeth look pretty good.

Scraping from 3rd gear stop washer.

Teeth before Dremel.

Teeth after.

Bearing surface for 2nd gear looks excellent.

_________________
-Austin
My 1974 Standard Beetle Build:
http://www.thesamba.com/vw/forum/viewtopic.php?t=492617

[19-VW-74]

Here are a couple photos showing how the detent keys for the 1/2 clutch hub and slider fit. Unlike 3/4 slider, there are only three specific teeth that allow the detent keys to fit.

Note: This is before I modified these parts with oil grooves/holes.

Key fits in this way:

Assembled with springs. Spring OD needs to be checked against Bentley spec and, if necessary, adjusted by light bending.

_________________
-Austin
My 1974 Standard Beetle Build:
http://www.thesamba.com/vw/forum/viewtopic.php?t=492617