Anyone know?

[OldBeachBob]

I've got a 1975 FJ55. Can I swap out the 4:11s for a set of 3:70s out of a FJ60? Gas mileage is killing me

Anything I need to watch for? I have an FJ 60 Disc Brake/ Power steering swap on already?

Should I just swap FJ60 complete axels in? Any issues with that?

Thanks much guys!

 

[3_puppies]

only issue might be the driveshaft flanges, fairly easy to remedy.

you should have fine spline inner axles, they'll match right up with the 60 diffs

problem with using the entire assembly is the width 3" wider than stock. you would need to outboard the front spring hanger on the pass side.

 

[n2666s]

was having the same milage problem on my 74 and ended up swapping the front and rears off of "piggup" a 79 pig that was parted out by a forum member; IIRC 78s and 79s have the 3.7 axles; now getting over 13 MPG with disk front end; an easy bolt on swap; thought about the fj 60 swap but there was going to be a bit of mods and I needed my girl for work..........HTH

Lou

I've got a 1975 FJ55. Can I swap out the 4:11s for a set of 3:70s out of a FJ60? Gas mileage is killing me

Anything I need to watch for? I have an FJ 60 Disc Brake/ Power steering swap on already?

Should I just swap FJ60 complete axels in? Any issues with that?

Thanks much guys!

 

[bigsal]

only issue might be the driveshaft flanges, fairly easy to remedy.

you should have fine spline inner axles, they'll match right up with the 60 diffs

problem with using the entire assembly is the width 3" wider than stock. you would need to outboard the front spring hanger on the pass side.

So, are you saying that the 'guts' from the 60 axels could be installed into the 55 diffs on his pig with only a replacement of the flange being the biggest issue? Would the flange from the original diff bolt up? Sorry for the silly questions, but I have not dove into that part of any of my trucks before. There is a 60 for sale down the street that doesn't have a straight panel on it... pretty trashed on the outside, but I am considering offering $350 for it... I know it runs, has discs and power steering...

 

[ridgerunner]

So, are you saying that the 'guts' from the 60 axels could be installed into the 55 diffs on his pig with only a replacement of the flange being the biggest issue? Would the flange from the original diff bolt up? Sorry for the silly questions, but I have not dove into that part of any of my trucks before. There is a 60 for sale down the street that doesn't have a straight panel on it... pretty trashed on the outside, but I am considering offering $350 for it... I know it runs, has discs and power steering...

The original flange should bolt up since they're both "4 speed" driveshafts, at least it's the case with the OP's 75.

If it was me, I would go get the whole FJ60 and swap in the drivetrain, unless you're going for a purist look. Better 4 speed, stronger and quieter (and potentially lower geared) transfer case, better steering system, wider axles with better brakes. I'd do it in a heartbeat.

 

[3_puppies]

the flanges will not swap, course spline and fine spline.

if the driveshaft flanges don't match you can use the matching ones from the 60 and use the short end of each and install on your 55 shafts and mount them the other way. they will be mismatched but it's quick and easy. all the slip joints are basically the same.

 

[cruiserbrett]

I did this swap 10 years ago and there isnt a day I regret it.

You will need to re-drill the round FJ60 flanges if you have a 74 or earlier driveshaft for some reason. If you get early FJ60 thirds the driveshaft pattern is the same as you 75. post 85 and its not, so again, drilling. Axle splines are same, so keep the 60 series diff thrust washers, and side gears in order, so you can re-use.

BTW, with the tired F motor, swapped in 4 speed, and the 3.70's I averaged 17.5 mpg across the country and back(7600 miles) when I drove my 73 FJ55 to Rhode Island and back from San Diego.