1G Input shaft seal replacement Manual 1990 GST

[Rice Burner]

I'm trying to verify if the input shaft seal has to be replaced from the inside of the manual tranny. I'm replacing the seals on my 90 GST that's been sitting up for many years. I've started at the timing side and been replacing all seals I can access. The ones I've pulled out have been hard and non flexible so they definitely needed to be replaced. I'm now at the trans side and replacing the clutch, PP, TOB, and planned to replace the output shaft seals, but noticed the inside of the bell housing is pretty greasy and I believe the input shaft seal was leaking from before. Hard to tell since the car hasn't been driven and no obvious oil leaks, but regardless it probably wouldn't be a bad idea to replace that seal based on the condition of the others. I've been trying to find a write up on what's involved in replacing that seal and a step by step with pics would be great. I'm not really finding anything for the 1g. Hoping someone has been down this road and has a link with some good info on the procedure.

Thanks in advance!

 

[pauleyman]

I'm trying to verify if the input shaft seal has to be replaced from the inside of the manual tranny. I'm replacing the seals on my 90 GST that's been sitting up for many years. I've started at the timing side and been replacing all seals I can access. The ones I've pulled out have been hard and non flexible so they definitely needed to be replaced. I'm now at the trans side and replacing the clutch, PP, TOB, and planned to replace the output shaft seals, but noticed the inside of the bell housing is pretty greasy and I believe the input shaft seal was leaking from before. Hard to tell since the car hasn't been driven and no obvious oil leaks, but regardless it probably wouldn't be a bad idea to replace that seal based on the condition of the others. I've been trying to find a write up on what's involved in replacing that seal and a step by step with pics would be great. I'm not really finding anything for the 1g. Hoping someone has been down this road and has a link with some good info on the procedure.

Thanks in advance!

Yes it's inside. Requires trans disassembly.

 

[Rice Burner]

Yes I realize that. I'm looking for a link or input on the best way to take the trans apart and back together. I don't want to do more work than is required so looking for a good write up or link.

 

[pauleyman]

Yes I realize that. I'm looking for a link or input on the best way to take the trans apart and back together. I don't want to do more work than is required so looking for a good write up or link.

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[Rice Burner]

Thanks, this video will be a big help. Much appreciated

 

[twicks69]

To do the job, read up: 1990-1999 F5M33 Transmission Disassembly:

To work on the transmission most effectively for teardown, you will want it on a tray / cardboard to catch any fluids draining off, and lay it out with the bellhousing side facing down / 5th gear cover facing up.

You will want the following tools:

snap ring pliers - https://a.co/d/g6gtZRl - Link to Titan 51901 lock ring pliers
seal puller - https://a.co/d/5W0ZZHa - Link to Lisle 56750 seal puller
OTC 1122 bearing splitter - https://a.co/d/0lNi66j - Link to OTC 1122 splitter
OTC 7393 push-puller - https://a.co/d/3Mjn6Sw - Link to OTC 7393 push puller
Miller MD998321 seal installer (special tool for input shaft seal installation)
3/16" cabinet tip flat head screwdriver - https://a.co/d/7x9ihuj - Link to Klein 601-4 screwdriver (for unstaking the shaft nuts)
36mm socket (end shaft nuts)
1/4" tip pen magnet pick up tool
3/8" drive torque wrench
12mm socket
12mm deep socket
14mm deep socket
17mm socket
19mm socket
24mm deep socket
swivel-head socket attachment - https://a.co/d/gXU5MXl - Link to Sunex 3301 socket
3/8" drive short 3" extension
3/8" drive medium 6" extension
2 prybars - medium sized with thinner tips
1/2" impact or cordless impact
3/8" impact or cordless impact
3/8" ratchet
3/16" roll pin punches (standard and extended length) - Proto J49316 works well
vise grip pliers
air hammer with a point tip attachment and 3/16 punch attachment are useful tools to have
hammer or mini-sledge
dead-blow hammer
Permatex Ultra Grey or Ultra Black RTV silicone
Brake-cleaner for degreasing purposes
Metal trays for cleaning purposes

These are the majority of the tools required for teardown.

For FWD (F5M33) transmissions:

Remove the 5th gear cover (12mm long and short bolts), place prybars in pry spots on cover to remove it from the case and place aside. The reverse cone wave spring might fall off, just put it aside for now. You are now looking at the 5th gearset with the 5th intermediate shaft smaller gear, and the 5th input shaft larger gear and 5th/Reverse hub and slider assembly / 5th/Reverse shift fork and reverse synchro on top. Use your hammer and 3/16" straight blade flathead screwdriver to pound out the stakes on the end shaft nuts so you can remove them.

Now, once the shaft nuts are unstaked, with one hand pressing down on the reverse synchro to keep it in place, use your other hand to manually shift the transmission shift select lever into reverse (5th/rev hub and slider will move upwards to engage the synchro). If you have access to compressed air and an air wand, grab a rag and the air wand and blow out the detent areas on the end shaft nuts to remove any debris that may get caught between the shaft nut and the threads on the shafts. Then, use your 1/2" impact and 36mm socket to remove the end shaft nuts.

With the shaft nuts off, and still engaged in reverse, you will now have limited access to the 5/R shift fork roll pin from the backside using your 3/16" roll pin punch. You will not be able to remove the roll pin by hitting it from the front side of it, because the roll pin will jam against the 5/R hub and then you will have more problems. By hitting it from the backside enough to get it to move a 1/4" outwards, then you can use your vise grips pliers and grab onto it straight forward on using the tip of the vise grip parallel to the tip of the roll pin. With it tight enough, you should be able to work it in a rotating / pulling motion and remove the roll pin from the shift fork. Only on 97-99 F5M33 and W5M33 transmissions can you hit the roll pin out from the front side because they have an offset roll pin orientation that does not interfere with the 5th/Rev hub; while 1990-1996 F5M33 and W5M33 transmissions do not have an offset roll pin orientation and do have interference with the 5th/Rev hub.

Shift back into neutral, then using your two prybars (ideally with thinner pry tips), place the prybars UNDER 5th gear synchro, above 5th gear engagement teeth, prybars evenly spaced, and pry upwards to separate the 5th/Rev hub and slider assembly and remove. Remove 5th gear and 5th needle bearings. Now, remove the 5th intermediate gear. It could be easy to remove by hand, or hard to remove requiring special tools -- DO NOT PRY THE GEAR OFF!!! YOU WILL CHIP THE TEETH! Use the proper tool. That would be an OTC 1122 bearing splitter and OTC 7393 push-puller tool by inserting the jaws on the top flange of the 5th intermediate gear and then remove the gear with the special tool, 19mm socket and cordless impact.

Remove the reverse switch and crush washer (24mm deep socket), remove the reverse lockout bolt and crush washer (19mm socket), remove the three shift detent poppet plugs (14mm socket)/springs/detent balls (using your pen magnet tool), and reverse idler gear bolt and crush washer (14mm bolt next to front differential passenger-side axle seal).

Remove case section bolts using your 14mm deep socket and 6" extension with your impact, and remove case section gently using two prybars evenly spreading the case gently upward. ***NOTE THE ORIENTATION OF THE REVERSE IDLER GEAR*** You will need to have the reverse idler shaft oriented properly so that the reverse idler gear shaft bolt properly reinstalls -- note the direction that is required so it matches up with the transmission case for easy installation. The black plastic main case oil guide may fall off, there is a slot it is retained by on the gear cluster case section.

Now, with the case removed, lift up on the reverse idler gear shaft and remove the shaft, then slide out the gear and remove the key from the reverse linkage arm. Remove the two 12mm bolts that attach the reverse linkage arm to the bellhousing using a 12mm short socket and swivel with 3" extension and impact. Remove the linkage arm.

Remove the front differential and output shaft.

Now, using your 3/16" roll pin punch and vise grip pliers, set up the pliers as a holder for the roll pin punch. Using your hammer and pliers with roll pin punch, remove the roll pins for the 1/2 and 3/4 shift forks.

With the selector in the neutral position, rotate the 5th/Reverse and 3rd/4th shift rail ends away from the selector (to the right) using your hands or gently using a small prybar. Orient the 5th/Rev rail end first by pulling upward and away from the shift selector. While the 5th/Rev rail end is up/away, do the same with the 3/4 rail end so that it clears the shift selector assembly. With the 1st/2nd rail end, go the OPPOSITE DIRECTION to the left while moving the shift selector and cage away from it and with the 1/2 rail end cleared of the selector, grab the two shafts with shift rails/forks and pull upwards. All the gear clusters and shift rails/rail ends/forks will come up as one single unit.

With the gearset removed, you now have access to the input shaft seal. Use your seal puller and remove the input shaft seal and install a new one. I use the OEM special tool Miller MD998321 to install the new shaft seal.

Inspect entire assembly and clean transmission case and magnet of any debris. Clean the case sections of RTV on the flanges and have everything fully degreased and cleaned off.

With new seal installed, assemble the gear clusters with the shift forks just like how you removed them originally. Reinstall the cluster assembly, modulate the shift rail ends just like how you removed them to get them all back to centered orienation with the 1/2 on the left side of the shift selector, the 3/4 on the center of the shift selector and the 5th/rev on the right side of the shift selector in the neutral position.

Reinstall new roll pins for the 1/2 and 3/4 shift forks. (M5x24mm works, or MD701722 are the OEM roll pins)

Reinstall the reverse linkage arm and 12mm bolts - 16-18 lb/ft torque. Reinstall the reverse linkage key, idler gear and slide the idler gear shaft back into the oiling detent with the bolt hole orientation towards the front diff properly so it aligns with the main case section. If you have to, look at the main gear cluster case section to see where the hole on the case is for the reverse idler shaft is and look at its orientation to the case bolt holes to get it properly oriented.

Reinstall the output shaft and front differential.
Reinstall the case debris magnet tray.

RTV silicone both sides of the case section flanges evenly with a thin bead of Permatex Ultra Black or Ultra Gray RTV silicone. Otherwise, using your finger, evenly spread a thin coat on the case section flange so that all contact area is evenly covered with the RTV silicone. Now install the black plastic oil guide back onto the gear cluster case section and install the case onto the bellhousing. Use your screwdriver or roll pin punch to orient the reverse idler rail correctly and install the reverse idler rail bolt and crush washer to get it started.

Reinstall the reverse idler gear bolt to 29 lb/ft torque. (Tapered end bolt with aluminum crush washer).

Reinstall the 14mm bolts that attach the main case section to the bellhousing to 29 lb/ft torque EVENLY.

Reinstall the 19mm reverse lockout switch bolt and crush washer (19mm head with spring-loaded detent ball on the end and aluminum flat washer) to 22-25 lb/ft torque.

Reinstall the 24mm reverse switch (plug head with 24mm hex-shape body and aluminum crush washer -- DO NOT FORGET THE WASHER or you will have problems shifting into 5th/Reverse) to 22-25 lb/ft torque.

Reinstall 5th intermediate gear and 5th gear split needle bearings/5th gear. Reinstall the 5th/Reverse hub and slider gently/evenly with 5th and reverse synchros with the keyways oriented properly so it does not bind up or get damaged. Slide the hub and slider back on WITH THE 5th/Rev shift fork at the same time being installed onto the 5th/Rev rail. You can use a socket and hammer to gently tap the 5th intermediate gear back into place, and the same goes for the 5/R hub and slider assembly.

If you do not have a 1/2" impact, and only a torque wrench, you can engage two gears by shifting the transmission into 1st gear, and then manually press down on the 5th/Rev slider to engage 5th gear. With both gears engaged you can install the end shaft nuts and use a torque wrench and 36mm socket to tighten the shaft nuts.
OR
If you have a 1/2" impact, you can simply reinstall the 5th/Rev shift fork roll pin, then install the shaft nuts, shift it into reverse with hand pressure to retain the reverse synchro while engaging reverse. Then use the impact and 36mm socket to tighten the shaft nuts.

Ping the detents with either a punch/hammer or a small point punch on an air hammer GENTLY for both end shaft nuts.

Reinstall the poppet balls, springs and plugs. I use Loctite 290 green wicking medium thread locker on the poppet plug threads. Torque the poppet plugs to 22-29 ft/lbs.

RTV transmission case flange for 5th gear cover and main gear cluster case evenly.

Be sure your reverse wave spring is still in place and reverse synchro is properly reinstalled. If your wave spring fell off during disassembly, you can reinstall it on the reverse cone of the 5th gear cover with the two locking tabs oriented in the slot of the casting, press down on it until it is locked onto the reverse cone, rotating it to confirm that the tabs are locked into place in the correct orientation.

Be sure that you have the roll pin back in the 5th/Rev shift fork, and that the transmission is back in the neutral position.

Reinstall 5th gear cover, tap down with a dead blow hammer gently to have it seated, and then evenly install the 12mm bolts to 16-22 lb/ft torque (FWD cases use this number; AWD cases with 14mm bolts use 26-30 lb/ft torque).

This is a quick rundown of directions for replacement of an input shaft seal or inspection/disassembly of a F5M33 FWD turbo 5-speed transmission for a 4G63 FWD turbo DSM 1991-1999.

Non-reusable parts mentioned -

FWD trans:
End Shaft Nut - MD731948 x 2
Roll Pins - MD701722 x 3
Input Shaft Seal - MD741818
Reverse lockout and reverse switch crush washers are 14mm ID / 22mm OD / 1mm thick aluminum crush washers.
Reverse idler rail retaining bolt crush washer is 10mm ID / 14mm OD / 1mm thick aluminum crush washer
Fill plug crush washer is 16mm ID
Drain plug crush washer is 18mm ID

 

[1990TSIAWDTALON]

You can't get any better than that post from @twicks69

 

[twicks69]

Well, taking pictures, or simply reading a factory service manual specifically for the F5M33 transmission portions always helps. But a detailed step-by-step is always a nice thing to have!

 

[1990TSIAWDTALON]

You're a very humble man Tim! Have a Merry Christmas

 

[Rice Burner]

Twicks69, thanks for this write up on the process and tools needed. I didn't realize I had more responses to this thread. I pretty much have all the tools for this. Now to psych myself up for this job, oh and to clean up some space on one of my garage shelves to lay everything out.