Transmission Diagnosis Help.

Hey guys, you know that DSM's aare notorious for breaking trannies. It isn't because they are weak, it's because of how they are driven.

Transmission Diagnostics.

Gear Clash (Grinding noise when shifting):

a) Worn blocker rings (This is part of the synchronizer assembly).

b) Clutch not disengaging properly

Clicking Noise (Heard in one single gear with the vehicle in motion).

a) Broken or chipped part of gear tooth (It can be on the main gear, on the countershaft(clutch shaft) or output shaft (main shaft).

Generally Noisy (In all forward speeds)

a) Low lubricant or incorrect lubricant
b) Transmission not securely mounted

Growling Noise (With clutch engaged and transmission in neutral -- will also be heard on acceleration as a steadily increasing whirring).

a) Worn or faulty input shaft(Clutch shaft, main drive gear) bearing

Growling Noise (With the vehicle moving in all gears).

a) Worn or defective countershaft or bearings

Growling Noise (Heard in all gear ranges except 4-5.

a) Roller bearings that supports the main shaft at the front that is in the rear of the input shaft. These are either damaged or were missing (If you overhauled your transmission and forgot to put these back in).

Violent Banging/shudder (Heard and felt in the vehicle just starts to move--- this is caused by abuse).

a) Broken main drive gear teeth.
b) Broken main clutch gear teeth.

Slips or jumps out of gear (Visually occures on acceleration and deceleration.

a) Loose synchro hub on the main shaft splines.
b) Worn synchro insert grooves on the synchronizer sleeve.

c) Bearing at the front of the main shaft disintegrated causing the shaft to wobble.

d) Worn detent mechanism

e) Worn thrust washers/helical gear axial movement.


Anyway, those are the basics. So if you are having any of these issues, consider this write up.

Jesse

The earlier trannies sure were weak! I have broken 2 of them and only one 92+ tranny.

Pre 92 trannies are butter/wood combination. Ask the tranny guys on here.

My tranny has 255000kms on it and I never had one problem with it.

Miguel than you are the man for having the original tranny lol. My 2g 2nd gear synchro assembly took a crap on me before.

LOL, I just service mine on a regular basis Jesse and it shifts beautifully.

I think you're right when you say they break down due to the way people drive them but I say the majority of them fail because of lack of maintnance.

If you maintain a tranny well but can't shift for beans, your tranny will fail on you. However, it won't fail as fast as a person that doesn't maintain the tranny properly.

1. People shift like maniacs

2. Lack of maintainence.

equals = Broken tranny

My AWD went 240,000kms with about 100-150 hard launches, and lots of banging gears on the original stock tranny. My FWD now has about 230,000 on the original tranny and CLUTCH =) and it still shifts smooth.
I agree with Sergio, all about the maintenance.
edit, and keeping the beating it takes within its limits, redline dumps and 8000+ rpm shifting will drastically cut these trannies lifespans down.

Alright guys. Everyone that babies there trannies and have got a lot of mileage from them should list the things they do. For example, changing the tranny oil after 15,000 KM or someting.

When we try to double the horsepower without upgrading the tranny, there shal be no expectations or complaints

That being said, I think we've got it pretty good. Just use good fluid often, and try not to make any mistakes.

speaking of trannies... my buddy has offered me a tranny and tail stock for mmy car. its a evo that allows you to change from awd to fwd. anyone heard of these? are they strong? or will i really just be wasting my time?

The switchable parts are just as strong as the standard stuff. They may have better syncros though. The transfercase will have an aluminum housing nad will be lighter than stock.

Whether or not you want to bother with the trouble of putting it int ehre for the switchable properties is up to you though.

Handy if you want to go to the dyno often, but otherwise not really useful.

I wasnt aware that Evo's came with these. I thought they only come out of GVR4s.

The EVOs don't, but i wasn't going to argue because it simply won't matter to him what car the parts came out of. But since you asked, and you have a clue about these parts, i figured i'd mention it

Nick I thought that the shift forks and rails where much weaker in the pre 92 trannies which would include the switchable? Holding them in my hands after I broke them they sure seemed less beefy than the 92+ stuff.

The switchable parts themselves are no weaker than the non-switchable parts.

Having switchable parts does not mean that the tranny has the same shift forks or other parts as any particular year of North American tranny. I have seen switchable parts on JDM trannies with both the weak aluminum forks and the stronger aluminum forks and the steel forks.

Well my tranny sounded like metal on metal in 1st&2nd, poped out of 5th with 245k's on a N/T tranny, pulled her apart and bingo the inputshaft and couple of other bearings wear worn, replaced those, seals and a 5th-rev synco and she's smooth as can be with 269k's and turbo @ 15psi, just shift proper and maintain them as said.
I drive my car hard, always have, but you gotta shift right with these cars!

Anything after 91' had ungraded syncro's and are stronger, and shifter better for longer.

I have 178km's and mines decent but still makes some humming once in awhile or grinds when cold... but I think it's because of the wrong fluid in tranny, what is the best fluid I can put in it? I wanna change it this weekend also what about the transfer and rear diff, thanks.

Personally, I used GM Synchromesh in my gearbox and TC of all DSM's I've owned, and always plain old 80w90 gear oil in the rear end.

You should use a good gear oil int he TC as well as the rear end. Something with EP (extreme pressure) additives is a good idea, especially if you're making good power.

Watch out with the N/T tranny, the tooth pitch is smaller, and they will strip off the gear if you feed it too much torque. Right Tim?

Any recommendations for gear oil? Some of the best.. some of the worst? I would like to overhaul my tranny in the spring... (330000 highway).

I use the 85-ep90 from CT that comes in the 5 gallon pails for about $35. It's cheap enough to change when you change the engine oil, and has served me well.

I use the recomended Mopar synthetic manual trans Lubricant 75W-85, P/N 04874459, it's expensive if you don't know someone who owns a garage. My old mitsu mirage, which has the same inturnals as the N/T, wouldn't shift in the winter well, so I put Lucas trans-fix mixed with ATF and it worked like a charm.
Adam Clay at Eastway Chrysler gives club discounts, and will know what your asking for.

I always been hearing how the BG synchro shift makes a huge difference in shifting. People say it cures notchy shifting. I am just wondering if it really makes that big of a difference.

i have noticed a difference with BG syncroshift, in my awd's. used to run castrol sytech gear oil. Back to the original post, very good info, seems about right to me. and yes the 2nd gear double snycro trannies are stronger, but not in all areas just a few things are stonger otherwise there the same. just did my 4th rebuild for a beater awd i got, and alot of the stuff is the same. if anyone needs any tips i have learned what to do and not to do when building one. the 93 one i build for my good car i beat the crap out of. not problems, just make sure to do the shaft/bearing preload correctly, otherwise quick shifting sucks, maybe ok for the normal driver though...