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EA82Turbo

What is my gearbox ratio?

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Hi all :)

 

I have a ea81T engine but I don't think the gearbox is standard. The gearbox is 5 speed with 2wd, 4wd hi and 4wd low. Currently I have a 3.9:1 diff on it but are not sure if it is the right diff?

 

Would the car be drivable with the wrong diff?

 

How would I test the gearbox ratio?

 

Cheers

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Pull the front axles, count the number of spline on the stub axle, 23 usually mean a N/A tranny with a 3.90 ratio, if the count is 25, it usually means it is a turbo tranny with a 3.70 ratio. Not 100% fool proof, but is right probably 99.9% of the time for a 5 speed D/R on-demand 4WD tranny

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In 2 wheel drive, yes. In 4 wheel drive, no. the rear differential just freewheels until you engage 4wd. One easy way to check is to jack up both wheels on one side of the car, put 2 chalk marks on the tires, both at the same place, put the car in 4wd and turn the wheels. If the chalk marks still match, the diffs are the same, if they don't, you need a new rear diff.

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Gee, if you can figure out what the tranny ratio is, and you can see the decal on the rear diff that tells you the ratio there, why would you have to do all that wheel spinning???

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the ea81 turbo was not available with the 4wd 5spd (not in the US anyway. )

 

you describe a dual range lever. there were part time dual range (23 spline) and full time dual range (RX)

 

but if its in an ea81 body, which used 23 solined axles, mos likely you have a part time 4wd dual range from a non turbo, which will have a 3.9 gear

 

go find soem sand or loose gravel, engece 4wd and see if she binds up or not

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Chalk marks and jack stands won't give you the tranny ratio and that is what he is looking for. Pulling axles is easy if you know the trick, and since he wouldn't be completely pulling the axle, this won't be even easier.

 

Fox and Shadow, the 85 and 86 RXs had the part time 4WD trannies and 3.70 ratio, plus 25 spline stub axles, actually the Fulltime 4WD trannies didn't show up until the 87 1/2 model.

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My test wll tell you if the front and rear diffs match though, and thats what he cares about. My bets are on the 3.9, mostly because they're more common, and the prevous owner would have (or should have) alerted him if he had swapped in a 3.7 tranny, but not the rear diff.

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