4 bolt and 3 bolt rear end question.

[pj91gsx]

I want to swap parts between a 3 bolt manual rear end and a 4 bolt automatic rear end. I am putting this into my 91 manual gsx. What would I need to do to make my 3 bolt into a 4 bolt rear end?

 

[BootlegGreg]

You would have to take out the ring and pinion from the 3bolt and put it in the 4bolt. Autos had a smaller gear ratio than manuals. Make sure you set the preload and re-shim the bearings on that 4bolt. I would take it to a rear end shop if i was you.

 

[pj91gsx]

You would have to take out the ring and pinion from the 3bolt and put it in the 4bolt. Autos had a smaller gear ratio than manuals. Make sure you set the preload and re-shim the bearings on that 4bolt. I would take it to a rear end shop if i was you.

I do realize the different gear ratio. I was thinking I could just change the axles and the internal parts that the axles slide into and use my 3 bolt differential.

 

[BootlegGreg]

Is the 3bolt a viscous? Otherwise there is no reason to put non lsd guts into a diff that already has them. If you just change the gears it would save you a lot of trouble. A good 4bolt manual rear end is only like $200-300 used.

 

[pj91gsx]

They are both Viscious. I got this one for free so Im going to see what I can do to try to make it work. Im thinking that I could just leave the ring gear and pinion in and change the axles and the inner parts that the axles rest in. Does that make sense?

 

[BootlegGreg]

Just make sure the spline count is the same on both axles. I have only changed to a 4bolt and have never tried to interchange axles. From what i know the spline part of the 4bolt axle is beefier and probably doesn't mate to the 3bolt. Let us know how it works out. It would be cool if they do interchange.

 

[pj91gsx]

I know that the 4 bolt axles will not go straight into the 3 bolt differential. I was talking about changing the spline in the 3 bolt diff with the spline from the 4 bolt, without having to mess with the ring gear and pinion.

 

[Mark4g63t]

Ever figure it out? I'm about to put the ring and pinion gears from a 90 5 speed into my 95 auto lsd rear diff. Was wondering if anyone has a write up or anything they used.

 

[Bud92gsx]

Would the auto rear gernade in a manual car?

When folks do the auto to 5 speed,5 speed to auto they always do the whole thing.There has to be a reason Why.

 

[Mark4g63t]

yea if you just put it in without changing the gears, the t-case I believe will go out.

 

[sillycon]

You need to change the ring and pinion to keep the final drive ratio correct between the trans and rear diff. If you don't, it can wreak havoc on all sorts of different things - axles, tires, t-case, viscous, center diff, etc.

Do the 4 bolt swap as usual (axle cups, axles, pumpkin), and swap the ring and pinion from the 3 bolt pumpkin into the 4 bolt pumpkin.

That said, folks have pushed the 3 bolts DEEP into the 10's. Given this, you can always run it as a 3b until you pop an axle or two.

 

[Mark4g63t]

Alright thanks guys, I should be good to go then