3 Speed/ 4 Speed Transfer Compatibility Question? (1 Viewer)

[NikP]

I have a 3 speed transfer mated with my 4L60E that has a high pitched whine. It was rebuilt before the install so I know it looked good internally.

I'm thinking about swapping in a 4 speed transfer I can pick up locally and rebuild. I know I'll need a different input shaft from Advance Adapters For the 4 speed.

A couple of questions:

Are the gears cut any different in a 4 speed case to possibly be less noisy?

I'd like to retain my existing driveline flanges to not have to rework drivelines. I assume the 3 speed flanges and parking brake will interchange. Is that correct?

I'd also like to retain the vacuum shift ( I know most think just replace with twin sticks but I kinda like it) . Will it bolt directly on the 4 speed front output nose cone or will the 3 speed nose swap to the 4 speed as a single compatible unit?

Thanks.

 

[brian]

the later split cases are quieter, but a non split 4spd isnt going to be that much less whiney to be worth the effort.

 

[NikP]

the later split cases are quieter, but a non split 4spd isnt going to be that much less whiney to be worth the effort.

Yeah the split case is the way to go but it requires an entirely different $1000 AA Adapter and then new drive lines and such. Going that route I’m likely in for $2500 or more if I can find a case near me. I’m not sure that route is worth the money.

With the 4-speed route I’m probably in at $500-600 which I’m willing to do for some improvement although I know it’s not all the way to the split case.

 

[brian]

Yeah the split case is the way to go but it requires an entirely different $1000 AA Adapter and then new drive lines and such. Going that route I’m likely in for $2500 or more if I can find a case near me. I’m not sure that route is worth the money.

With the 4-speed route I’m probably in at $500-600 which I’m willing to do for some improvement although I know it’s not all the way to the split case.

its not that much of an improvement

 

[Living in the Past]

The driveshafts difference is not that much. SOR shows the FJ40 1/74-84 being the same. Only difference is the hand brake moved to the rear axle 8/80.

Not sure what AA charges for the sixteen spline input shaft but at one time SOR use to sell ten spline thirty one teeth input gear that would allow the adapter to be used as it is. This gear was use on the 4/75 and later one piece transfer cases still running a three speed. If the output shaft long enough to use the bearing at the back of the case that bearing might need to be change. I know some adapters use a short shaft. Obvious with a split transfer case a whole different adapter would be needed.