Mismatched Transmission and rear diff

[skiahfrazier]

Hello folks. I have an EA swapped brat. They used the AWD transmission from the donor car. I am guessing it is the 4.1 : 1 ratio. How would I be sure? Are there identify numbers anywhere? I have the stock 3.9 Brat rear diff. And now the is some noise coming from the drive train when driving. Not when sitting. How reliable is the Brat rear differential when used full time? Should I be scouting for an early legacy differential? If I swapped to a legacy diff, does it require a special driveshaft? Thank you for your assistance.

Kind regards

[skishop69]

Do you mean EJ swapped as in they put in an EJ engine? Easiest way is put it in neutral and push it. It should roll easily. If it doesn't, you've probably got different ratios. Any idea what year, make, model the swap came from?

[wagonist]

drop the transmission sump plug.  It's close to being underneath the front diff.

Need to jack the car up so you can spin the driveshafts, then you can count the teeth on the crown wheel.

There's a few different EJ transmissions

3.9

4.1

4.4

at least

 

But if you've used an EA transmission, there's only 2.

3.9 & 3.7

 

EJ type rear diff will bolt directly into the back end of a Loyale style. Not sure about the earlier models, but I'm pretty sure you can fit an EA type rear diff into an earlier car, so not really any reason you couldn't. someone else with more knowledge about the earlier car can comment.

 

the only catch with the EJ rear diff is you need one from the Gen 1 Legacy as it has external splines. You can use diffs from a later model, but you'll need those external stub axles (they just snap in) from a Gen 1 Legacy.

Edited November 8, 2016 by wagonist

[skiahfrazier]

Thanks! I purchased the Brat with this done. I was not aware of the mismatch possibility until I did some reading. I have no way of knowing what year the EJ parts (engine and transmission) came from. But I can guess early, as there is not an OBDII plug anywhere. It does roll down my slightly sloped driveway with the clutch pushed in. i don't know if that means anything. Work is keeping me away from hoe a lot lately, do I don't have much time to check on things right now. But plenty of time to ask questions and brainstorm. Thanks again for the information.

[DaveT]

When I added 4WD to one of my wagons, I inadvertently used a mis-matched diff.   When I switched 4WD on, I could feel the car load up.  It would be draggy and slow quicker than when in 2WD mode.  It would get going in snow faster in 4WD than 2WD, but get squirrely once moving along, since the front / back would be breaking traction..   I eventually figured out the the transmission I had chosen was the only on I had with a slightly higher ratio, from my 86.  When I swapped it out, everything was good.

[crazyhorse001]

If you have an EJ with an ea trans you will have an adapter plate between the engine and trans. If you have the ej trans, it will have a sticker on the left near the starter. Google the numbers on the sticker. The. You'll know model year and ratio of the trans.

It's not rocket surgery or brain science, it just subies.

[Numbchux]

If you have an EJ with an ea trans you will have an adapter plate between the engine and trans. If you have the ej trans, it will have a sticker on the left near the starter. Google the numbers on the sticker. The. You'll know model year and ratio of the trans.

It's not rocket surgery or brain science, it just subies.

 

This.