3rd and Drive slipping bad

[dan_j_b]

Today I noticed my tranny slipping in 3rd and drive. I drove it about 100 miles today and it went from being able to go 75 ok once the torque converter locked up to barely holding 65 in 3rd. It slips if you give it any gas, but works fine in 1st and second.

From what I have read, this is the high clutch failure. This transmission is from a 92. I have a tranny from a 95 that suffered some sort of front diff. failure. The case is cracked around the front output shafts so I assume there are some broken parts inside the front section.

I am wondering if I would be able to make 1 good tranny out of these 2. Would I be able to use parts from the 92 tranny to fix the 95? Would this require anything like setting gear lash or would it be more like unbolting parts and swapping them?

I'd like to get my SVX back on the road before it gets too snowy up here.

Thanks
Dan

[Earthworm]

You should be able to make one good transmission from the 2. I haven't opened one up myself so I don't know all the details.

That's exactly how mine failed.

[dan_j_b]

Are there any cheap parts I should replace or anything else I should do while I"m in there?

[NeedForSpeed]

Hi Dan,

According to 'young' Tom, you can swap the diffs by using the pinion gear AND matching shim from the donor trans. Remove the old pinion and shim, install the donor and then mount the front housing with ring using some grey prep. Make sure you have the small rubber seal between the housing and main box!

To remove the pinion shaft, remove the tail housing. Put the trans in P, then use a 35mm or 1 3/8"? socket to remove nut. tap shaft out.

It is possible to mount your good diff onto the good box.
Thanks again for shipping parts from your busted engine!


Are there any cheap parts I should replace or anything else I should do while I"m in there?

[crotchrocketony]

IM looking to do the same. I rebuilt my trans due to playing in the snow to hard and messed up my 1st/r clutch pack(welded together) well after the rebuild it only lasted like 6-10k and the 3/4 started to slip bad. we think it was from a cooler being a bit cloged...I did a cooler flush kit and installed a new trans. well the guy that put it in for me forgot to put diff fluid in the front diff....well I got half way home and the diff got noisy. I got some gear oil and found the speedo gear melted to the dip stick.... so now I have a good trans with a F-ed diff and a good diff and a f-ed 3/4 clutch in the trans. so im going to pull the trans and try to swap the diff (and replace the flex plate..he had a dowel pin still in the old trans......so it cracked the flexplate) I need a new grease monkey once he is finished fixing what he broke !!!

[TomsSVX]

well, I can take care of that for ya...

Tom

[TomsSVX]

Hi Dan,

According to 'young' Tom, you can swap the diffs by using the pinion gear AND matching shim from the donor trans. Remove the old pinion and shim, install the donor and then mount the front housing with ring using some grey prep. Make sure you have the small rubber seal between the housing and main box!

To remove the pinion shaft, remove the tail housing. Put the trans in P, then use a 35mm or 1 3/8"? socket to remove nut. tap shaft out.

It is possible to mount your good diff onto the good box.
Thanks again for shipping parts from your busted engine!


Now for you guys who have a little grease monkey in ya have to know that hypoid gear sets are matched and will fail if they are not. So make sure you use the matching ring and pinion gears. If it is possible, use the front diff case as a whole... meaning, do not take the carrier out. Just pull the housing off the trans and pull the pinion out of the trans... Do the same with the bad diff trans and reverse the procedure on the good trans using the good gears... Hope this makes sense... it can be intimidating but it sure isn't rocket science

Tom

[NiftySVX]

Now for you guys who have a little grease monkey in ya have to know that hypoid gear sets are matched and will fail if they are not. So make sure you use the matching ring and pinion gears. If it is possible, use the front diff case as a whole... meaning, do not take the carrier out. Just pull the housing off the trans and pull the pinion out of the trans... Do the same with the bad diff trans and reverse the procedure on the good trans using the good gears... Hope this makes sense... it can be intimidating but it sure isn't rocket science

Tom
All true, but you'll need to reset the backlash. You may need to replace the shim behind the pinion, too. This is not a procedure for the shade tree mechanic. Also, keep in mind that the SVX hypoid gear set is no longer availible.

[svxistentialist]

You should get the Subaru 4EAT Technical manual from ATSG.

Their website is www.atsgmiami.com

The 4EAT book is $25, well worth it if you are doing your own work.

http://www.atsg.biz/cgi-bin/shopper.cgi?preadd=action&key=EIMP83-SUBA4TM&pricecode=&reference=/cgi-bin/shopper.cgi%3Fsearch%3Daction%26keywords%3Dall%26s earchstart%3D0%26template%3DTemplates/SearchResult.html%26category%3DEIMP%26pricecode%3D

Joe:)

[TomsSVX]

All true, but you'll need to reset the backlash. You may need to replace the shim behind the pinion, too. This is not a procedure for the shade tree mechanic. Also, keep in mind that the SVX hypoid gear set is no longer availible.

It is very hard the measure backlash once the case is put together... You only have the drain plug to use for access. So it takes a finger to measure it... If it is off, the case needs to come off and new shims added/removed... I have done this before at least 5 times now with great success and none of these times have I had to add/remove the shims if you use the shims from the pinion gear

Tom

[dan_j_b]

Well I took the newer tranny apart. Here are some pictures. I got that ATSG service manual (thanks for the tip svxistentialist) and it came apart pretty easily. As you can see, the gears are pretty messed up in it. It looks like the transmission was suddenly stopped (put in park) while the car was moving, shearing those teeth off. If anyone has any other theories, feel free to chime in. I have made a list of seals, o-rings and gaskets to replace while I"m in there. Now all I have to do is pull the one out of the car and swap everything around.

Dan

[crotchrocketony]

i have a quick question....how is the pinion gear removed? im going to do the diff swap thursday and i dont want to get bit in the ass when I have it all pulled apart....do I take the 4 bolts out and pull it apart with the bearing? (I wouldnt be dealing with this if the guy put diff fluid in the front diff when he put my new trans in! she is a wineing and the speedo gear (the green plastic part) is melted...probly the cause of the wine is the plastic melted and slung everywhere

[dan_j_b]

Yes you have to take those 4 bolts out around the pinion, but first you have to remove the extension housing at the back, then with the tranny in park, remove the lock nut on the bottom reduction gear, remove the gear either with a puller or if you already have the bolts out in the front, carefully tap the shaft forward, seperating it from the gear. from there it should pull right out the front

Dan

[crotchrocketony]

yeah thats how I thought I rembemered it from the last one I rebuilt....but it has been a few years..... thanks...do you think I can just use my diegrinder to smoth the rwd clutch hub so stop my slight binding I have going on? I know it is groved and my old one is groved all the same...i know I won be able to get a new one in time for when I have it pulled apart....just a thought ( I have gotten away with doing it like this on a motorcycle clutch hub that was hanging up like these do)

[svxistentialist]

Well I took the newer tranny apart. Here are some pictures. I got that ATSG service manual (thanks for the tip svxistentialist) and it came apart pretty easily. As you can see, the gears are pretty messed up in it. It looks like the transmission was suddenly stopped (put in park) while the car was moving, shearing those teeth off. If anyone has any other theories, feel free to chime in. I have made a list of seals, o-rings and gaskets to replace while I"m in there. Now all I have to do is pull the one out of the car and swap everything around.

Dan

Glad you got it, no problem.

If you have seen the Subaru shop manual, these pics are all copies of it, so the info comes from the factory.

With two boxes the same, you should have enough spares to make one working set.

Good work.

Joe:)

[TomsSVX]

Looks like the case cracked.... drained the fluid and burned up the pinion bearing thus killing the gears... I would put money on the pinion bearing being loose and noisy

Tom

[dan_j_b]

Yeah the pinion bearing doesn't sound too good when I turn it. My only question with your theory is how did the case crack? I think the crack was the result of the damage, not the cause.

[TomsSVX]

Could have been... The #1 cause for gear wear is the pinion bearing taking a crap... I guess the cracked case was just a result of the worn gears meshing inproperly and breaking the case... How do the seals look on the axles?? If those go bad, the gear oul leaks out and that can cause bearing failures.

Tom

[oab_au]

I would say that the failure started with the crown wheel being forced away from the pinion gear. Unfortunately the front diff isn't very strong, the pinion is firmly held in a steel plate, that is bolted to an aluminum housing that holds the crown wheel.
Any extreme or sudden loads, like front wheel spin will distorting the aluminum case, allowing the crown wheel to move away from the pinion. This moves the tooth load out to the tip of the tooth, that eventually breaks off from the load. The broken tooth piece jams between the two gears forcing them apart to break the case.

They did reinforce the case to help with the distortion, at some stage, so it may be only in early models.

Harvey;)

[crotchrocketony]

I did my diff swap last ngiht. not bad at all. so when this trans mission blows up (I have no faith in it being this is #3) Im guessing I could buy a legasy trans and then just swap the front diff so I dont have to mess with the rear

[dan_j_b]

oab_au - Thats true, but how can you explain the fact the the pinion gear is sheared off on one side, but the rest is perfect and the crown is bad all the way around? the pinion had to be locked in that position while the crown continued to turn.

crotchrocketony - The SVX uses a gear ration of 3.545 for the front and rear. As far as I know, there is no other subaru box that uses that. you could swap in some 3.90's or 4.11's for extra fun, but you have to change the rear diff too.

[oab_au]

oab_au - Thats true, but how can you explain the fact the the pinion gear is sheared off on one side, but the rest is perfect and the crown is bad all the way around? the pinion had to be locked in that position while the crown continued to turn.

crotchrocketony - The SVX uses a gear ration of 3.545 for the front and rear. As far as I know, there is no other subaru box that uses that. you could swap in some 3.90's or 4.11's for extra fun, but you have to change the rear diff too.

The loading on the pinion teeth, is at least 3.5 times higher than the loading on the crown wheel teeth. The diameter of the gears, makes the difference.

As the case distorts the crown wheel moves away from the pinion gear to move the load out to the pinion tooth tip. So the pinion breaks a tooth off first, keeps rotating to damage the crown wheel teeth. The next pinion tooth is then impact loaded to break off next, until there are a number of pinion teeth off.

Harvey.;)

[dan_j_b]

Yes, but if you look at the picture, there are only a few teeth broken on one part. 2/3 of the teeth are still perfect. The pinion gear obviously stopped turning before the teeth were broken off.

[Trevor]

The loading on the pinion teeth, is at least 3.5 times higher than the loading on the crown wheel teeth. The diameter of the gears, makes the difference.

As the case distorts the crown wheel moves away from the pinion gear to move the load out to the pinion tooth tip. So the pinion breaks a tooth off first, keeps rotating to damage the crown wheel teeth. The next pinion tooth is then impact loaded to break off next, until there are a number of pinion teeth off.

Harvey.;)

Not a correct answer.

The exact loading being questioned is the lateral forces involved, as would be required to distort the case. Not subsequent loading on the pinion teeth, which involves gear diameters.