torxxx Posted February 9, 2006 Share Posted February 9, 2006 Alright I've heard both answers now. Some say I'll have to change the 3.7 rear diff to a 3.9 rear diff when Mr. Pink gets the 5 speed conversion done to his GL wagon with a 3AT in it. I've also heard that you dont have to change the rear diff unless we'd be changing the final drive. Well isnt changing the tranny's a form of changing the final drive? What ratio is the 3speed AT? 3.7 rear diff so I'm guessing 3.7? 5 speed D/R is 3.9 so tis final drive is 3.9? God, I hate numbers.... they scare me Link to comment Share on other sites More sharing options...
idosubaru Posted February 9, 2006 Share Posted February 9, 2006 i hear your pain, i'm trying to figure out gear ratios in another thread and it's cumbersome. there are two differentials, one in the front and one in the rear. the front is connected to the transmission so it comes out when you pull the trans. if the trans you're installing is different ratio then you need to swap rears too. so to answer your question, changing transmissions is not a form of changing final drives, unless the front diff attached to it is different than the one you took out. if they are both 3.7 or 3.9 then you're not changing the final drive, the front diffs are the same final ratio. NA dual range 4WD transmissions should be 3.9 from what i've been seeing. i thought the 3AT was a FWD only transmission? why won't my posts let me seperate paragraphs? ? Link to comment Share on other sites More sharing options...
torxxx Posted February 9, 2006 Author Share Posted February 9, 2006 yeah i just noticed that too. first we lose our sigs now we can't press return...... they are really pushin for donations now... lol Link to comment Share on other sites More sharing options...
Dylan86GL10 Posted February 9, 2006 Share Posted February 9, 2006 Gary, I've got that 3AT slushbox in my PT GL10. When I pull the PT 5pd from Brad, I'm going to have to check to see if the rear is the same or not or that is coming too. Link to comment Share on other sites More sharing options...
idosubaru Posted February 9, 2006 Share Posted February 9, 2006 i'd grab the driveshaft and rear diff while you're there. you already have to pull the shaft out of the trans anyway. two 17mm bolts at the center support and three bolts to drop the rear diff, knock out the axle pins and you got the driveshaft and diff for 5 bolts. and you'll probably unbolt the center support anyway to remove the trans, so 3 more bolts and you got it and the rear diff to go with you. Link to comment Share on other sites More sharing options...
Qman Posted February 9, 2006 Share Posted February 9, 2006 yeah i just noticed that too. first we lose our sigs now we can't press return...... they are really pushin for donations now... lol Shadow is in the middle of an upgrade. He reopened the board early but still has to finish our tweeks to the system. Be patient, it's better to have a almost complete system than not one at all. Link to comment Share on other sites More sharing options...
tailgatewagon Posted February 9, 2006 Share Posted February 9, 2006 its been said before but i guess it will get posted again all autos. 3.7 gear ratio. all non turbo manuals 3.9 gear ratio all turbo manual 3.7 gear ratio xt6 3.9 gear ratio(the only ea car that had the option for a 3.9LSD(not VLSD) i think that covers it........................................ Link to comment Share on other sites More sharing options...
TROGDOR! Posted February 9, 2006 Share Posted February 9, 2006 I'll say it again, as I've said it many times before- ALL nonturbo sedans/wagons are 3.9, and ALL turbos are 3.7. 3AT's are available in both 3.7 and 3.9 just like the manuals, it all depends on whether the car is turbo or not. The owner's manual says all autos are 3.7 final drive, THIS IS A MISPRINT. All nonturbo EA82 sedans and wagons are 3.9 final drive, manual or auto!!! I've been under enough to notice, and I've also replaced two 3AT's with junkyard units, which I checked for gear ratio BEFORE pulling. I also converted a nonturbo Loyale from 3AT to Dual Range and didn't change the rear diff, and it matches the final drive from the manual tranny perfectly- just ask Tin Soldier, he bought the car from me and will tell you it runs smooth as silk in 4WD. When dealing with EA82 sedans/wagons/coupes, this is all you need to know, for manuals and automatics: TURBO: 3.7 NONTURBO: 3.9 And while I'm at it, all 4cyl XT's are 3.7 final drive- manual or automatic, turbo or nonturbo, all the 4cyl's take a 3.7. The XT6 manual takes a 3.9, and I haven't ever checked under a 4WD auto XT6, so I can't say for sure on that trans. Or you can just crawl under the car, scrape the dirt off the rear diff tag, and verify it. Link to comment Share on other sites More sharing options...
RONAN Posted February 9, 2006 Share Posted February 9, 2006 I maybe misunderstanding??? But my 87 4wd GL wagon had a non-turbo spfi ea82 with a 5spd Hi/Lo and a 3:70 LSD rear diff. Link to comment Share on other sites More sharing options...
85Sub4WD Posted February 9, 2006 Share Posted February 9, 2006 Trogdor - I am sorry to disagree, but it depends on the specific vintage - the 1985 MY ALL used 3.7:1 rear diffs, you have to read the FSM to get the transfer ratios - the FSM AND the owner's manual agree I have personally seen several working NA 3AT cars from 1985, all with the 3.7 rear from the factory - the ratios for the 3AT changed along the production line - the 4WD transfer reduction ratio also changed (manuals use a 1:1, autos use somewhere around ~.9:1 - depending on year) - it is NOT just a matter of turbo or not Bottom line - compare the two diffs, and keep the diff matched to the tranny - that is the safest way to be sure you have them matched correctly Rohan - you may have had a modified 3.7 LSD, which had its gears changed to 3.9:1, but kept the LSD mechanism - it is a relatively common mod Link to comment Share on other sites More sharing options...
TROGDOR! Posted February 9, 2006 Share Posted February 9, 2006 1985 is actually the only year I haven't done tons of work on. Interesting. I know for a fact 1986 takes a 3.9, as I used a 1986 trans to replace a 1990 that most definitely was 3.9. Checked the diff on the '86 before pulling it as well, to confirm. Link to comment Share on other sites More sharing options...
RONAN Posted February 9, 2006 Share Posted February 9, 2006 Trogdor - I am sorry to disagree, but it depends on the specific vintage - the 1985 MY ALL used 3.7:1 rear diffs, you have to read the FSM to get the transfer ratios - the FSM AND the owner's manual agree I have personally seen several working NA 3AT cars from 1985, all with the 3.7 rear from the factory - the ratios for the 3AT changed along the production line - the 4WD transfer reduction ratio also changed (manuals use a 1:1, autos use somewhere around ~.9:1 - depending on year) - it is NOT just a matter of turbo or not Bottom line - compare the two diffs, and keep the diff matched to the tranny - that is the safest way to be sure you have them matched correctly Rohan - you may have had a modified 3.7 LSD, which had its gears changed to 3.9:1, but kept the LSD mechanism - it is a relatively common mod 85SUB4WD, Don`t want to argue, but it was factory. I bought it new off the dealership lot. Now you`ve got me wondering if I had a one of a kind ??? Believe it or not, the car is still limping around town. I`ve talked to the present owner a while back and the car has over 350K miles on it at that time. It had been T-boned in the side and does`nt have hardly any metal left on the body LOL. Totally rusted. He bought it for $100 and uses it to haul his merchandise to the local flea market only. The drivers side front CV-halfshaft is blown and he runs it in 4wd Hi, relying on the rear...RONAN Link to comment Share on other sites More sharing options...
Dr. RX Posted February 9, 2006 Share Posted February 9, 2006 1985 is actually the only year I haven't done tons of work on. Interesting. I know for a fact 1986 takes a 3.9, as I used a 1986 trans to replace a 1990 that most definitely was 3.9. Checked the diff on the '86 before pulling it as well, to confirm.Well, I just checked the Subaru Parts manual, 85 to 90, it shows a non-LSD 3.70 ratio rear diff for all those years, some of the models shown are turbos, but others are not, so why would a N/A have a 3.70 rear diff? There are 5 different auto trannies from 85 to 90, 1 for 85 & 86, 1 for 87, 1 for 88, 1 for part of 89, and 1 for 89 and 90. The latest Factory Service Manual the I have in the house if for 1986, it shows the auto tranny as having a 3.70 ratio. I will check the other FSMs that I have outside and see if I have one for one on the years in between 87 to 90. Link to comment Share on other sites More sharing options...
TROGDOR! Posted February 10, 2006 Share Posted February 10, 2006 What are the differences between the trannies anyway? I put an 88 trans in an 87 car and an 86 trans in a 90 car, and both went in and ran perferctly, like they were made to fit. Never had the slightest bit of trouble with installation or operations. I don't doubt that there is some difference (Hollander lists them as different too), but it sure wasn't in the electronics, final drive, axle shafts, mounts, input and output shafts, etc... essentially everything that gets attached to something else was the same. Could the parts listings possibly be wrong? I hear they also list a 3.9 LSD, yet I haven't heard of any documented cases of one existing outside of an XT6. Just food for thought. Link to comment Share on other sites More sharing options...
TROGDOR! Posted February 10, 2006 Share Posted February 10, 2006 The latest Factory Service Manual the I have in the house if for 1986, it shows the auto tranny as having a 3.70 ratio. I will check the other FSMs that I have outside and see if I have one for one on the years in between 87 to 90. Well, either the service manual is in error, or they offered either final drive for 1986. As I said I used a 1986 model trans in a 1990 model car, both of which had 3.9 tags on the rear diff, plain as day. I ran that 1990 wagon all day long in 4WD at the Pine Barrens without the slightest binding, so I know for a fact the trans had a 3.9 ratio. The car I pulled it from was most definitely a 1986- it had the 85-86 bumpers, grille, trim, gauge cluster, interior, etc- not to mention the junkyard employees had written 1986 all over it. Also had a 12/85 build date. Link to comment Share on other sites More sharing options...
Dr. RX Posted February 10, 2006 Share Posted February 10, 2006 Well, either the service manual is in error, or they offered either final drive for 1986. As I said I used a 1986 model trans in a 1990 model car, both of which had 3.9 tags on the rear diff, plain as day. I ran that 1990 wagon all day long in 4WD at the Pine Barrens without the slightest binding, so I know for a fact the trans had a 3.9 ratio. The car I pulled it from was most definitely a 1986- it had the 85-86 bumpers, grille, trim, gauge cluster, interior, etc- not to mention the junkyard employees had written 1986 all over it. Also had a 12/85 build date.You might be able to get away with different ratios in the front and back on the auto trannies, since they are basically FWD trannies until you push the 4WD button. Even then you might get away with it since the bands in the auto would be more forgiving then the gears in a standard tranny. It could be that the reason why you were changing the tranny was that the person who owned (or someone prior) the car, changed that read diff, not knowing about the tranny having a diff and that the ratios needed to match. All I know is that every EA82 car that I have been under that had an auto tranny has had a 3.70 rear diff. Link to comment Share on other sites More sharing options...
TROGDOR! Posted February 10, 2006 Share Posted February 10, 2006 Well I'm not trying to say you're wrong Corky, since you do know these cars inside and out... but I've never seen a nonturbo auto with a 3.7 diff. I just wonder what the big mystery is. I think next time I'm at the junkyard I'll look under the cars and see what I find. There was also that one I converted from 3AT to D/R without touching the rear diff, and it runs smooth as silk in 4WD. Link to comment Share on other sites More sharing options...
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