Tranny noise

[XSNRGGST]

Recently I noticed a sound coming from the passenger/tranny side on my 97 GST. It is most predominant when I am in 4th or 5th gear and cuising with a little bit of throttle. The sound is hard to describe because it is neither a definate grinding or whining. Kind of in-between. The sound stops when I stop pressing the gas, but it seems to be there also when I am slowing down in lower gears (2nd/3rd) withough pressing in the clutch pedal.
It almost seems like it could be some kind of sound coming from the intake filter as well.


This sound has seemed to just show up in the past two weeks. I have 124,000 miles with a 2100 ACT clutch, aluminum flywheel being installed at 89k. The tranny fluid was replaced at 114k with BG synchrochift fluid. No problems shifting, but it does get a little sticky when I want to put it in reverse after starting it in the mornings. I usually put it in 2nd first without engaging the clutch, then shift over to reverse to get it into gear without it grinding.
Also, I have blown motor mounts for the front and probably rear as my 3" exhaust now rattles as it bumps the rear frame/crossmember becuase the engine is torqued a bit.
Could this incorrect alignment of the motor be part of the problem?

Any ideas?

Need more info like a sound clip to help? Let me know what is the best way to capture this if needed to help in diagnosis.

Thanks so much!

Eddie

 

[Boosted_Curse2]

motor mounts can cause a large number of problems. how long have those 2 mounts been bad? if they have gotten worse in the amount of time you say the noise coming fro myour tranny has become apparent, I would start with the motor mounts first.

 

[twicks69]

Fix the motor mounts first, then if the problems from the transmission persist...

Do the following:

Inspect your axles (inner and outer CV joints for damage or looseness), then

Either bring it to a professional Mitsubishi mechanic shop, or learn to do it yourself...


If you want to learn to do it yourself, then I would want to first check the input and intermediate shaft end nuts for tightness first, so...

Use a 24mm 1/2" drive socket and 1/2" ratchet and remove the drain plug to drain the transmission and inspect the fluid; if it is brassy looking, it is a synchro issue. If it is a silvery color or there is debris in it, get ready to just pull out the transmission for a rebuild.

If there is no debris in large quantities floating around, then lets pull the 5th gear end cover to check the shaft nuts.

Tools needed: Car jack, jack stands, 36mm 1/2" drive socket, a good 1/2" impact gun, a metal punch (small head), 12mm short and deep 3/8" drive sockets, 3/8" ratchet, flathead screwdrivers, and a small prybar, Permatex Ultra Black silicone gasket maker, metal hammer and dead blow hammer.

I attached a few pictures to help you along if you do it yourself.

Lift car up, and place jack stands. Drain the transmission and inspect fluid. Remove the 9 short (~3" long) and the 2 long (~10" long) bolts that hold the 5th gear transmission cover using your 12mm socket/ratchet -- a 12mm gear wrench works otherwise for a few of them. (Picture #1). Picture #2 shows all the bolts removed. The 5th gear cover should come off fairly easy, but may take a little persuasion with a flathead screwdriver or small prybar to separate it from the transmission. You should now be looking at Picture #3.
Picture #3 shows the viscous coupler at the top, which is held in place with a snapring -- you don't need to remove this part for the task we are doing. The middle shaft is called the intermediate shaft, and the outer shaft is the input shaft. The output shaft holds the reverse synchro -- which is LOOSE; be careful to not drop it off the transmission. If you want to replace the reverse synchro, now is the time. Contact your local mitsubishi dealer and purchase the part (MD746439 -- reverse synchro) -- see Picture #4 so see the reverse synchro. The End shaft nuts are: MD746439 (2 of them if necessary).

Both shafts have STAKED shaft nuts that you will be using the 36mm socket on ONLY IF THEY ARE LOOSE. Check the stakes on it to make sure the nut hasn't moved. If the nuts have moved you will need to retighten them and re-stake the nuts into their detents using a hammer and metal punch or replace them with the part number above.

If they are tight, and everything looks good, you have other problems. Inspect the 5th gear end cover; clean it good, then look at the reverse cone eave spring for damage and the reverse cone itself for wear; also check the three bolts holding the reverse cone to the cover for tightness (picture #5). If the reverse cone is toast, then you likely have damaged/worn out tapered roller bearings on the input shaft.

If there is no damage, then it can be anything from your tapered roller bearings on the input or intermediate shafts starting to fail, to gear damage or excessive wear. If this is the case, look for a professional to do a rebuild. If the rebuild is necessary, I reccomend Jacks Transmissions (www.jackstransmissions.com -- http://www.jackstransmissions.com/p...id=19&osCsid=e394e2853e4355ec43c88ea5042acc41 ) and John Shepherd (www.sheptrans.com -- http://www.sheptrans.com/details.php?sid=34 )

I hope that this helps and not hurts.

 

[95blackGsTurbo]

Did you check your pilot bearing/bushing when the clutch was changed. It will cause noise when coasting but not when on the gas.

 

[XSNRGGST]

Twicks,
Thats what I am all about thank you very much for the very helpful post!
I am very much a DIYer. My wife is not so trusting though. She wants me to take it in to our mechanic. I just don't want to spend the money, even though he gives us a great deal on labor.

One question:

If the fluid is brassy, indicating a synchro issue, what is the next step? Rebuild?

 

[twicks69]

Personally, yes.

If it is excessive, it could mean that the synchros are on their way out, but you would see it if your currently having grinding issues.

I really hope that it is a damaged CV joint for your sake, and not a transmission rebuild.

 

[laserspeeddemon]

I suggest taking a look at the clutch itself first. ACT had a bad fun of clutches before. It's hard to describe, but if you get your tranny out. Stick your finger into the spline of the clutch and see if it moves at all (maybe a mm or two). If that is the case, then your tranny was misaligned upon re-installation.

 

[JackM]

It sounds like you have bad intermediate shaft bearings. That is becoming very common on these units now that they are getting old. I would suggest that you stop driving the car until you figure it out. If any of those tapered rollers get loose in there, you will be looking at serious tranny damage. BG is known to cause excessive bearing, hub thrust, and fork wear. It makes it shift nice, but wears out a lot of parts quickly.

Jack
www.jackstransmissions.com

 

[twicks69]

Jack! I didn't know that you were on this forum! Good to have you in on the conversation!

 

[XSNRGGST]

I also have had Driver's side torn inner CV joint boot for a little while now. Could this also be the problem? It isn't that bad as just the boot came apart at the small end of the boot. I was going to replace it myself but...

My wife doesn't trust me with DIY repairs and she hasn't let me deal with it. I told her about it about a month and a half ago, but she didn't want my to handle the problem myself as she wants to take it in to our friend's shop. We haven't done so yet. Looks like it has cost us a whole axel replacement.

I am trying to get on top of these simple maintenance problems, but she is not so willing to comply.

1. Torn front motor mount with possible rear/sides
2. Torn Driver's side inner CV boot
3. Oil leak from front case/timing belt side