DIY Transmission Repair - Part 2 - Splitting The Case

Advanced Member
Joined: September 15th, 2008, 9:11 pm

March 21st, 2009, 7:04 pm #1

Toward the bottom of this thread are instructions if you are unable to view the pictures. This pictorial is easily viewed via Google Chrome using those instructions.
You will find the necessary steps to take your transmission apart to a level allowing you to repair it or replace the complete input and counter rotating shafts from another transmission.
The entire sequence requires about 25 minutes labor once you put the transaxle on the bench - maybe more if it is your first time.
There are no special tools required, but the ones mentioned do make the process easier.
If you have someone to help you, it should be easy for you to 'split the case' and have the three shafts in hand in a half hour.
Do not be afraid of the detail. Once you've done it, you'll kick yourself because it really is easy.
Indeed, few mechanics can do what is included in this simple thread.
Transmission repair certainly separates the boys from the men.
Thanks to the Administrator/Moderators who prevented it from getting buried in the transmission section by giving it 'sticky' status.
You will find that the threads I mention below, which address the next steps in repairing the transmission: stripping the shafts of gears, replacing them etc. no longer have pictures, or the links don't work at all.
At the time of original posting, all the links mentioned had working pictures.
Thanks to the members who have added helpful information to the thread.
Thanks to Dattman who knows this stuff backwards and forwards.
Many transmissions have been repaired using only the steps mentioned here.
Originally, I was going to make threads on how to rebuild the shafts as well, but felt there was no need as others had done so and their threads were clear.
(Edited to thank the Administration/Moderation for pinning this link on 4/25/18.)

First you must remove your transmission using Johnny Mullet's thread:
"Manual Trans Removal /Clutch Guide; How to remove the transmission"
or get a loose transaxle from somewhere (junkyard, for example).
Then you can pull it apart to see what's wrong, if anything.
Second you learn how to take your transmission apart...down to the basic shaft assemblies.
Once you have completed these 25 basic steps (roughly 90 minutes for a first-timer) you should go to the next part:
Third - you inspect and repair the gears on the shafts as needed.
Originally, I directed the GeoMetroForum membership to this thread:
Which gave a picture heavy "how to take apart the two shafts and reassemble your transmission".
(Unfortunately- this "Hold on to your lug nuts" link has had the pictures removed by the author, so it is no longer helpful. Plus, at 11 pages, it is very long, and I believe he made some critical mistakes as the transmission didn't last long.)
As of this editing, my recommendation is:
The Factory Service Manual would be your best resource as of the date of this edit to help in rebuilding the input and counter rotating shafts.
Fourth, you reverse the sequence in this thread to put your transaxle back together.
Fifth, you install the transaxle into the car and hopefully drive off in the sunset a happy camper!
Originally posted on by Phil N Ed AKA pacapo a long time ago in Bethlehem hahaha:
wrote: Here's how to split your transmission case:

We begin using the earlier 'MK1' transmission (Not the later Metro black box style, however those instructions are included below).

Drain and Remove Transaxle.

1. Remove backup lamp switch.
2. Remove (7) bolts from the side case (#2 above) and remove side case.

3. Remove snap ring and hub plate

4. Remove shift fork screw and guide ball

5. With the transmission in neutral, remove the roll pin

6. Push in on gear shift shaft

...slide synchronizer sleeve toward center of trans (see arrow) to engage 5th gear

...another view

...unstake and remove 5th gear retainer

7. Remove everything in the brackets as a unit. #2 is showing what you want to avoid...
8. Remove 5th gear (drive) from the input shaft
9. Remove 5th gear (driven) from the countershaft

10. Remove 7 screws on retainer plate. Mark or tag spacer shims if present.

11. Remove 3 bolts on left case cap and remove cap.

12. Remove the roll pin using the correct diameter drift/punch

13. Install a drift into the roll pin hole and raise the shaft for removal of the yoke and roll pin.

14. Remove the bolt retaining the reverse spring and detent ball. Remove the spring and ball.

15. Remove the locating bolt for the gear hift/selector shaft.

16. Remove the 4 bolts of the gear shift guide case (#3 above)
17. Remove the gear shift/selector shaft assembly along with the low speed select spring (#1 above).

18. Remove the 3 bolts retaining the detent balls and springs as shown. Also remove the springs.

19. Remove 13 bolts which hold the two casings together. Here, two are left.

20. Insert a large flat screwdriver between the two casings as shown, and in three or 4 other locations.

21. Lift the left case straight up. All parts whill remain on the lower case as shown.

22. Raise 5th (#1 above) and reverse (#2 above) give clearance for removal of the reverse gear and shaft
23. Remove 2 bolts retaining reverse idler shift lever to the case; remove lever.

24. Remove 5th and reverse gear shift shafts together (as an assembly).

25. Remove remaining input and countershafts as well as the two shift shafts (everything in the white bracket) as an assembly (together).

That is the Factory recommended sequence. We simply added some real world photos to supplement your Factory Manual line drawings.

For a Metro transmission, check and see if you have the black side case (Black Box Tranny).
Here's one from 4 different angles:

Here's one.

another view

If you have that transmission here are a couple of differences:

#1. The reverse switch.

#2. The black cover has 6 bolts vs. 7 on an older style transmission. Two require a 12mm wrench.

The black box also has the oil filler plug in a different location.

Here are the two covers. The black has a more developed oiler for the input shaft.(not clearly visible in the photo)

#4. Remove shift fork screw and guide ball: the screw is now removed via hex wrench:

#6."...unstake and remove 5th gear retainer" The retainer is now larger(I think it's a 28 MM socket):

so you will have to use a 1 inch socket or hand wrench (or MM equivalent).

10. "Remove 7 screws on retainer plate. Mark or tag spacer shims if present." It is now 6 phillips screws. A "hand impact tool set" is highly recommended. There are no spacers due to a change in the input shaft bearings: they are no longer tapered roller bearings. The countershaft retains tapered roller bearings in a cage at each end.

12. "Remove the roll pin using the correct diameter drift/punch" Is now changed to "remove bolt..."

14. "Remove the bolt retaining the reverse spring and detent ball." Location of reverse bolt is as shown above. There is no spring or ball.

18. "Remove the 3 bolts retaining the detent balls and springs as shown. Also remove the springs."

You will note the two different size springs used to hold the balls against the shafts. The earlier models use one size only. Some suggest you do this step later so that the shafts and gears will remain in the right housing.

19. "Remove 13 bolts which hold the two casings together." The two bolts shown above are the only two accessed from inside the bell housing. Removing these at the start of disassembly might save you a few seconds.

The left case is very light. The black box trans has two points where you can safely pry the cases apart.

#22. Reverse can be removed without raising 5th gear.

Special Tools:

Impact hand held screwdriver (highly recommended-you can see it in use in #10 above)

Other Tools/Help:
Snap ring pliers
Drift/Punch/Allen wrench to drive out pin
Several Plastic 'Sandwich Bags'

to keep the different bolts, nuts, pins, etc. organized.
Reverse this procedure, being careful to install reverse correctly and the check balls and springs.
Those with questions regarding this procedure or other transmission/clutch related issues should post them in the "Transmission/Clutch/Axles" section. (edited to add new subsection of Metro Tech!)
Now, decide if you are going to work on the gears yourself or have a machinist do them.

Even if you are apprehensive, give the gears a try, GeoMetroForum is here to help!

Last edited by pacapo on April 25th, 2018, 1:44 pm, edited 6 times in total.

Elite Member
Joined: November 10th, 2008, 10:46 pm

March 21st, 2009, 10:19 pm #2

:gp WOW What a great post.. :thumb Thanks very very much for all the time and effort you put into this project. I am going to try and put it on a cd or a stick so I can keep it. One of the best "How to" I have seen. Thanks again. Mr Mullet Please pin this. :gp :drivin :drivin
Dreaming of Geos on the Gulf V 2017

Johnny Mullet
Elite Member
Joined: September 8th, 2008, 1:49 am

March 22nd, 2009, 1:43 am #3

pacapo, I really appreciate you posting this! Great job!

New Member
New Member
Joined: September 30th, 2009, 12:25 pm

October 2nd, 2009, 5:56 am #4

oh man!!! you are so cool
good DIY.!!!
:) :D
have learnt it
DYMEE - Auto Gallery

Advanced Member
Joined: November 27th, 2008, 11:58 pm

October 2nd, 2009, 4:04 pm #5

removed since pacapo IS 'phil n ed' on teamswift
Last edited by duff_remle on August 14th, 2010, 5:58 pm, edited 2 times in total.

Murf 59
Elite Member
Joined: July 2nd, 2009, 9:49 am

October 3rd, 2009, 2:41 am #6

Nice posting.
A 13.5 to 1 G10. With GTi twin cam pistons. Performance head package work sponsored by our friends at 3Tech.
A set of 4.38s set up as a 4 spd. MSD ignition, and a Weber card on top. It has a SRD header on the bottom side.
I run a Glow shift tach, and a HF vacuum gauge.
This engine is still in the works. I have all the pieces, but am not able to get the energy to assemble it.

This is what it looks like running at Bonneville from the front seat of a Geo Metro

Johnny Mullet
Elite Member
Joined: September 8th, 2008, 1:49 am

October 3rd, 2009, 4:03 am #7

duff_remle wrote:You should give credit to Phil N Ed or just link to his thread.
I was unaware :news

Credit given :deal

Phil N Ed is very helpful on TeamSwift :thumb

New Member
Joined: September 28th, 2009, 1:16 pm

October 23rd, 2009, 6:45 pm #8

Question on picture #5 You are removing the roll pin with a punch and sledge?? Does the roll pin stay on the punch? Help a blond out here :)

New Member
Joined: September 28th, 2009, 1:16 pm

October 23rd, 2009, 6:58 pm #9

Never mind....Im a dork!

Advanced Member
Joined: September 15th, 2008, 9:11 pm

October 28th, 2009, 3:14 pm #10

mzprfkt wrote:Question on picture #5 You are removing the roll pin with a punch and sledge?? Does the roll pin stay on the punch? Help a blond out here :)
The roll pin is 'punched through' and will not remain on the punch.
That's a fair question; therefore don't consider yourself a 'dork'.
You bring up a good point; try and use a punch with a diameter the same size as the roll pin's outer diameter, or a little bit less so that you don't end up spreading the pin, and making it harder to punch through.

Just a reminder, picture #5 is of an earlier model transmission than what you probably have.
Your transmission might be the second one that we did in the thread and starts with this picture:

(...actually, it's a female doing the black box disassembly, so how tough can it be?)

There will be a nice write up on how to do the gears, but here's a write up from "Dr. Bill" in Washington State:

DIY Tranny Rebuild, Page 1
If you can't click on the link above, here's the address: ... p?t=941461

DIY Tranny Rebuild, Page 2
Again, here's the web page: ... p?t=944174

He isn't using a press, and is trying to show an inexpensive way to swap out bearings, etc.

If you do decide to rebuild your gearbox at home, pay close attention to Dr. Bill's pictures, especially the one showing how the hub (the smooth looking double ring affair below the quarter) is oriented in this picture:

I believe he mentions that he borrowed this picture from another member, "Way".

Most people feel that using a shop press is safer and quicker, especially if you can pick one up used, or borrow a neighbor's.
I don't want to steal the thunder of the author of the next 'DIY' thread, so enough on that for now.

He does use a couple of techniques which cause him some pain, so plan on sitting for a half hour to read through his procedure before you decide which path to take.
Dr. Bill's thread should be commended especially on his cleanliness an his careful approach to the task.
Maybe I missed it, but it would have been nice if he'd mentioned his chemical brew for cleaning up those parts.

wrote:You should give credit to Phil N Ed or just link to his thread.
Phil N Ed on Teamswift is member #15 (by join date) on our GeoMetro Forum, so no need for credit. :thumb he just reposted it here so it would be easier for the members to look up.
He doesn't post much, as his Metro has no problems and changed his screen name on this Forum as his neighbor (Ed) moved years ago.
Thanks for the 'pump', the more of these cars we can keep on the road, the better.