1G AWD 5 speed questions

[laserRSawd]

I have a few questions about how to build my spare transmission. I just purchased rebuilt gear clusters that Jacks did in 2017, they were never installed. It includes an EVO3 input shaft and first gear. The transmission case vin shows its a 91, with the later shift levers. Intermediate shaft looks like the 90 style, the center diff having no line cut on the gear.
On intermediate shaft 3rd gear has one tooth is chipped almost 1/4 way. From the paperwork Jacks cleaned the tooth up. I do not like it.

I have extra parts from a small hub 3-4 92 trans and a large hub 93 trans. Of those two I have one intermediate shaft that is usable but also has a chipped tooth on 3rd. (smaller chip) The center diff from my 91 is in the best shape from what I have. I also have 2 90 transmissions that I have not torn down to look at them.

questions:
is the 92 up intermediate stronger ?
should I look for a 92+ intermediate and center diff? or look for another 91 intermediate shaft.
can I use the 91 center diff parts in the 92 center diff?
should I build it using the small 3-4 slider and gears?

the car will be on the street with occasional launches

first 2 pics are the 91 tooth cleaned up. last 2 are the 92 intermediate

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[pauleyman]

90 and 91 center diff and intermediate shafts will mesh. The difference is the 90 center diff uses different internal lower shins and its 90 only. 91 intermediate gear angles are the same as 90 but the needle bearing and hub spline surfaces are larger. Measure the shaft between the gears. It's larger on 91 (and 92 up). 91 is a 1 year shaft as was 90.
The smaller 90 splines and needle bearing surfaces are also why you can't do a double cone 2nd in a 90 without machining.

I built a 90 hybrid for myself not wanting to buy a center diff I used all 90 parts I had with a 91 intermediate so I could get a 93up 2nd and 91 up first so I get the double cone 2nd. Actually i did a gvr4 input and first gear but I wouldn't recommend that. I did it because I had a low power street car. Now I have an evo3 first gear and input shaft.

 

[92AWDHX40]

Pm tim zimmer he can answer all the questions.

 

[laserRSawd]

thanks, I did not know 90 and 91 were different intermediate shafts. I have measured the 2 shafts that I have out. The 91 is 1.655 and the 92 shaft is 1.658, very slimier. I do not have a 90 trans torn down for reference.
If I am correct then. I can get either a 91 or 92 intermediate shaft, use my current gears from the 91 and build a center diff that matches my choice.
The 91 intermediate cluster I have supposedly has a double synchro 2nd according to Jacks cluster build at the time. I have not pulled it apart to confirm.

 

[pauleyman]

thanks, I did not know 90 and 91 were different intermediate shafts. I have measured the 2 shafts that I have out. The 91 is 1.655 and the 92 shaft is 1.658, very slimier. I do not have a 90 trans torn down for reference.
If I am correct then. I can get either a 91 or 92 intermediate shaft, use my current gears from the 91 and build a center diff that matches my choice.
The 91 intermediate cluster I have supposedly has a double synchro 2nd according to Jacks cluster build at the time. I have not pulled it apart to confirm.

No. The third gears must all match.
90 and 91 and both the same third gear pitch. If you switch to 92 up intermediate you need a 92 up center diff and whatever choice 3rd 92 up You could do 92 smaller or 93 up bigger synchro but the bigger synchro requires other changes too. If you have a 90 trans there are further changes to forks etc. Make your selections wisely.

 

[laserRSawd]

Thanks. I was too focused on the intermediate shaft, i forgot about 3rd on the input shaft. I think I will hunt down a 91-92 intermediate so I can keep the small 3-4. That way I will be able to use my new shift fork and not have to swap shift rails.

 

[pauleyman]

Thanks. I was too focused on the intermediate shaft, i forgot about 3rd on the input shaft. I think I will hunt down a 91-92 intermediate so I can keep the small 3-4. That way I will be able to use my new shift fork and not have to swap shift rails.

That's still wrong. 91 and 92 intermediate are different parts.
90 and 91 intermediate share the same gear pitch but 91 shaft is bigger which also means the 1 and 2 needle bearings are bigger. 92 up intermediate changes gear pitch on 3rd.
Much of this is why nobody likes 90 trans. These aren't the only differences.

 

[bastarddsm]

That's not right 100% either pauley.

2 main time periods of gears, each has a 2 minor periods.

Begining of time till about mid 91 they all used the same pitch on 3/4 ishaft/cd body. They have to be kept as a set. They will generally not have any hashes on the teeth, cd for sure doesn't. IIRC sometimes 3rd might have 2 hashes, i-shaft might have some. There are 2 sub periods here. bot to mid 90, and mid 90 to mid 91. The earliest gears use a smaller spline and races for the 1/2 assembly. That means the 1-2 us unique to this period. Can't put a late model double synchro on them, no replacement 1/2 gears or hub available new. In mid 1990 they started using the big shaft, which means it has the same tooth profile on 3/4 but uses the late style 1/2 parts. You can put the late double synchro set on these, and these are my favorites to use.

so you can use a 3/4 part from prior to 91.5 in any trans prior to 91.5. But an early 1/2 parts are only good in early trans.

In mid 1991 they changed the 3/4 profile to one that's more peaky. The cd body has a hash, 3/4 will have hashes (3 i think), and so will the intermediate shaft. These gears 3/4 gears are not compatable with the stuff from before mid 1991. The 1/2 parts are backwards compatable till mid 90. The 3/4 hub/slider is compatable from bot till mid 1992.
in mid 1992 they change the 3/4 to use the larger hub/slider assembly. This uses the same size synchros as 1/2 and is supposed to be weak, I've not used them so i can't say from experience. You can back date a late trans to use the small synchro 3/4 from 91.5-92.5, and you can update an 91.5-92.5 to use the 92.5 stuff.

The important thing to grasp is you can't cross the 91.5 line with the 3/4 set. That's the cardinal rule of DSM transmisisons. Everything else is pretty well doable.

AFAIK 1/2 tooth profile is the same for all of dsm production so you could use a say 90 input shaft in a 99 trans if needed. Just gotta watch that extra spacer on the early input shafts. You can't put an early 90 first gear in a 99 trans however.

Then there is the evo and gvr4 stuff, but that's outside the scope here. i think.

OP I wouldn't trade out that the chipped shaft in your trans for another chipped shaft. Get the 90's apart and see what you got. Might have a late 90 in there which would be ideal.

Also virtually every 91.5+ trans I've taken apart has chips like this. I've run chips like this down into the low 10's. It's not ideal, but we are at the end of the line for parts.

 

[pauleyman]

That's not right 100% either pauley.

2 main time periods of gears, each has a 2 minor periods.

Begining of time till about mid 91 they all used the same pitch on 3/4 ishaft/cd body. They have to be kept as a set. They will generally not have any hashes on the teeth, cd for sure doesn't. IIRC sometimes 3rd might have 2 hashes, i-shaft might have some. There are 2 sub periods here. bot to mid 90, and mid 90 to mid 91. The earliest gears use a smaller spline and races for the 1/2 assembly. That means the 1-2 us unique to this period. Can't put a late model double synchro on them, no replacement 1/2 gears or hub available new. In mid 1990 they started using the big shaft, which means it has the same tooth profile on 3/4 but uses the late style 1/2 parts. You can put the late double synchro set on these, and these are my favorites to use.

so you can use a 3/4 part from prior to 91.5 in any trans prior to 91.5. But an early 1/2 parts are only good in early trans.

In mid 1991 they changed the 3/4 profile to one that's more peaky. The cd body has a hash, 3/4 will have hashes (3 i think), and so will the intermediate shaft. These gears 3/4 gears are not compatable with the stuff from before mid 1991. The 1/2 parts are backwards compatable till mid 90. The 3/4 hub/slider is compatable from bot till mid 1992.
in mid 1992 they change the 3/4 to use the larger hub/slider assembly. This uses the same size synchros as 1/2 and is supposed to be weak, I've not used them so i can't say from experience. You can back date a late trans to use the small synchro 3/4 from 91.5-92.5, and you can update an 91.5-92.5 to use the 92.5 stuff.

The important thing to grasp is you can't cross the 91.5 line with the 3/4 set. That's the cardinal rule of DSM transmisisons. Everything else is pretty well doable.

AFAIK 1/2 tooth profile is the same for all of dsm production so you could use a say 90 input shaft in a 99 trans if needed. Just gotta watch that extra spacer on the early input shafts. You can't put an early 90 first gear in a 99 trans however.

Then there is the evo and gvr4 stuff, but that's outside the scope here. i think.

I probably worded poorly between build date and model year date. I agree with what you're saying by build date. Build date (if it's known) is a better indicator. Build date loosely follows model year changes from what I've seen. I dont trust anything until I tear it apart.

 

[CrackedDSM]

I almost feel like this thread should be stickied. There's some golden information in here.

 

[laserRSawd]

Thanks all for the info. I believe my wording was wrong on some of my comments. What ever way I go, I will make sure gears match. I was not aware that there could be 2 different intermediate shafts that have the odd 90 center diff gear profile

I will see what the other 2 transmissions have in them and go from there. Is a true 90 intermediate shaft easy to spot or will I have to tear them down?

I agree that parts are getting hard to find. I hope to use the new evo input and first gear to build a nice transmission. I should have enough parts left over to get 2nd spare built that will be usable.

 

[bastarddsm]

I probably worded poorly between build date and model year date. I agree with what you're saying by build date. Build date (if it's known) is a better indicator. Build date loosely follows model year changes from what I've seen. I dont trust anything until I tear it apart.

it's hard even on that cause I've seen unopened factory 91 tran's with the early 90 stuff in them. And then so many have had stuff swapped around. I've had a 2g trans with a 90 gearset through my shop.

But yeah, get your eyes on it first is the second cardinal rule.


The only way to tell an early 90 without pressing it apart is the number on the gear, but even that's not 100% But I think most of the ones I've seen were 59 iirc. I've not worked on a trans in a month or two, but I got a bunch to do soon.

I personally don't like the evo first, it's too tall for a car with anything more than a 16g unless it's 2000lbs imo. Hard on the clutch and doesn't close up the 1/2 gap enough, but that's just me. dang dogbox is even worse. My car has been quickest with dsm first and evo1 finals. So like 11% lower than stock.

 

[pauleyman]

it's hard even on that cause I've seen unopened factory 91 tran's with the early 90 stuff in them. And then so many have had stuff swapped around. I've had a 2g trans with a 90 gearset through my shop.

But yeah, get your eyes on it first is the second cardinal rule.


The only way to tell an early 90 without pressing it apart is the number on the gear, but even that's not 100% But I think most of the ones I've seen were 59 iirc. I've not worked on a trans in a month or two, but I got a bunch to do soon.

There is another way. The shaft between 3 and 4 on the intermediate is smaller. To facilitate the larger splines and needles for 1st and 2nd gear on the later cars that section of shaft is also bigger. It's visible to the naked eye it's such a big difference. Casual glance you may not notice but side by side its obvious. I've seen a 90 intermediate shaft shear in half right under 3rd gear.

I personally don't like the evo first, it's too tall for a car with anything more than a 16g unless it's 2000lbs imo. Hard on the clutch and doesn't close up the 1/2 gap enough, but that's just me. dang dogbox is even worse. My car has been quickest with dsm first and evo1 finals. So like 11% lower than stock.

 

[laserRSawd]

little update. I tore apart a 90 style transmission tonight. It was the most grimy looking turd I have. inside all the gear clusters look great. the intermediate shaft measures the same in between the gears. I have a 65 stamped on first gear. I will press it apart tomorrow to make sure its the bigger shaft.

The center diff looks great, its the the best out of 4 that I have torn apart. little to no wear on the thrust surfaces.

I also think I need some kind of rehab/therapy of some sort. I'm 42 and now hauling car parts into the house.

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[pauleyman]

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The shaft between 3rd and 4th. That's how you tell. They are a significantly different diameter from 90 and 91 up. Sorry this isn't mine. Just a random pic. If yiu have several laying about a caliper should point it out quickly. If you have a 90 and a center diff that meshes you will find the 91 shaft when you find the bigger one that also meshes with the center diff from a 90.

 

[laserRSawd]

I have the same measurement on the recent tear down shaft as the 91 and 92 shafts I have out. The recent tear down center diff has no oil grove cut in the gear and meshes with the chipped 91 intermediate 3rd.

I do not know what a 90 center diff looks like inside but the recent torn down trans has the same guts as the 92-93 centers I have looked at.

with that, I am going to assume I have found a good intermediate shaft that will work with the rest of my rebuilt parts

 

[bastarddsm]

Put a pair together that is wrong, and see how they rock side to side. Put 2 together that are supposed to be together and see how the feel. Now you know how to tell for sure.

 

[laserRSawd]

I can confirm my recently tore down transmission intermediate shaft is correct for the rest of my gears. the area where the needle bearings also measure the same as the shaft in between 3-4.

one other quick question just out of curiosity I noticed the older organic lined 1-2 synchros have no teeth missing. The 92 style synchros have areas with large spacing between the teeth. is this for quicker engagement ?

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