Auto/Manual Rear Diff

Frosty2086 · Post by **Frosty2086** » Mon Apr 12, 2010 2:23 pm

OK so a mate of mine has an EA82 L series 1988 model. 3 speed auto transmission with electronic 4WD engagement. The transmission has exploded on him. But the engine is great.

We have gone out and aquired and old 1991 EA82 L series with a blown head gasket, unregistered for $200. 5 Speed manual, gear box and running gear is all in good nic. Cant rember the ratio, possibly a 3.9 rear diff.

The big question is. Can i bolt the Manual gearbox straight onto the rear diff that is fitted to the auto gear box? Do the auto models come with the same diff as the manuals, in either a 3.9 or 3.7 ratio? or were they different?

This will save a bunch of time removing diff etc. from the manual and putting into the rear end of the auto car to give us one operational manual suby.

Anyone done this before and know what the deal is with the auto rear diff?

Any hot tips are welcome!!

Cheers

Post by **TOONGA** » Mon Apr 12, 2010 6:20 pm

it will have the diff ratio written on it if it doesn't drain the diff mark one of the teeth you can see through the cover and then slowly count the teeth 37 teeth = 3.7, 39 = 3.9

and yes if the diff ratio is the same you as the manual box wont have to change it but you will have to use the transmission shaft (prop shaft) that goes with the manual transmission as the auto one is a different length

TOONGA

thatsgoodsquishy · Post by **thatsgoodsquishy** » Mon Apr 12, 2010 7:16 pm

Dunno if they are all the same but when I converted my 85 Touring wagon from auto to manual I had to change the rear diff as well as they didn't match.

Frosty2086 · Post by **Frosty2086** » Mon Apr 12, 2010 8:10 pm

Thanks for that guys. Will count the teeth and see how we go. Hoping the drive shafts dont need to be swapped to fit the new diff. I suspect the ratios will not be what we require knowing our luck!! Will be an entertaining time no doubt!!

YouTube · Post by **El_Freddo** » Mon Apr 12, 2010 8:14 pm

I think you'll find that the auto is 4.1 ratio OR 39/11. As toonga said, there should be a sticker on the diff.

Just change the diff. It doesn't take long. And that manual will be a 3.7... You'll love the manual.

Cheers

Bennie

RSR 555 · Post by **RSR 555** » Mon Apr 12, 2010 8:39 pm

An easier way to check your rear diff ratio is to jack up both back wheels (best to have the car on car stands) and with the gearbox in neutral, mark the front yoke of the diff and the front of the diff with a bright coloured paint pen (or scratch with a sharp instrument) then without moving anything yet, do the same to either side CV joint and side of the diff. Once all marked, this is where it's best to have 2 people (1 to turn the shaft and count and the other to call stop) turn the tailshaft in the normal direction (clockwise look aft from gearbox) and count the turns until the marks on the CV joint realign themselves again. If it's 3.7 then the mark on the tailshaft will be near the opposite side of the shaft and if it's 3.9 then it will be near the original mark.

Hope this is clear enough? if not just ask any questions

RSR 555 · Post by **RSR 555** » Tue Apr 13, 2010 8:46 am

Forgot to mention that the tailshaft should turn almost 4 times before the wheel would have turned once.

Also what Toonga has said regarding counting the teeth is good for people who has their gearbox out of a car and no matching rear diff with it.

steptoe · Post by **steptoe** » Tue Apr 13, 2010 10:18 am

I pulled same box out of my 86 turbo sedan, the front ratio is 3.45:1 and rear diff is 3.7. I was fortunate to buy an 87 made, 88 complianced touring wagon $250, coz I could still drive it (once I replaced the stuck shut thermostat down the road

) $ 200 if I couldn't, had thre weeks rego so I could really check the box and other bits out first.

If you are unlucky ratio sticker has gone. I was lucky, again, and found the 3.7: sticker on the back diff knowing it was same as my sedan. Rear diff swap is quick and easy to do so long as splines not rusted up. Reckon 3.9's are not common.

So, you have all the bits, manual starter motor, flywheel , clutch, pedal box, cable, console is just a click out the top bit of its selector surround and slot in the manual one, and the wiring at selector needs a loop on the no start in any gear switch wiring, extra thick black with yellow stripe? EASY and WELL WORTH DOING.

DO WHAT I meant to and forgot, the tranny drain plugs are usually in better condition, same thread I hope as manuals. Any probs PM me

Jonno

steptoe · Post by **steptoe** » Tue Apr 13, 2010 10:22 am

For starters, even if the diff ratio at rear is different can still drive it as FWD until you get correct rear ratio in so long as you don't chuck it in 4WD

I don't miss my old 3 speed auto 4WD no low ratio box one bit. Your mate will love it. Keep the rear section of tail shaft for a spare, the front bit is for the 3 speed auto only. Toss it too

Frosty2086 · Post by **Frosty2086** » Tue Apr 13, 2010 10:30 am

Definately will not be missing the 3 speed auto. I think it redefines gutless. Thanks for all the info guys. Wil probably put some stuff up for sale/giveaway in the next while from various L series. If your looking for bits we have two compelete cars - minus the manual transmission etc!!!