Driveline modification for 3spd to 4 spd swap?

[Road Hog]

I'm working on a 1971 J55 F 155 motor and considering a swap from 3 speed to 4 speed. I've heard the drive line will need modification. I have a drive line from my 1974 parts rig that is 48" and some. This was used with a chevy 350 with a bell housing adaptor. The driveline for the '71 is the same length. So I was wondering if anyone could tell me spec for the driveline length for a 71 J55 with a 4-speed swap? Thanks

 

[Skreddy]

I would wait until you do the swap, then measure for the correct length. Things like lift, which trans and t-case, all will impact how long you need.

 

[pb4ugo]

When i went from 3 speed to 4 speed in my 72 FJ40 I had a complete 77 FJ40 donor. I swapped everything and it all fit. I used everything from the 77. Bellhousing, Trans, tcase driveshafts. I had to swap rear pinion flange, and bolted in the disc brake front end. In your case, because the donor had V8, they likely moved the engine, so the driveshafts may not fit. I've never dealt with an FJ55, fyi.

 

[Road Hog]

Thanks,
I think the Bellhousing adaptor may have helped keep the length the same. It would be nice if it was interchangeable, but I think that is too much to ask.

 

[Road Hog]

I would wait until you do the swap, then measure for the correct length. Things like lift, which trans and t-case, all will impact how long you need.

I'm pretty sure it's an early H42 10-spline. The transfer case may be from a three-speed. It looks similar.

 

[Living in the Past]

Measure your current three speed driveshafts. Difference between three speed and four speed right around three and a half inches. That means the front driveshaft will need to be that longer and rear driveshaft will be that much shorter. Because the 74 had a V8 conversion it most likely will not b what you need since V8 is shorter transmission/transfer case were probably closer to the firewall than with a 2F. Haven't looked at a FJ55 frame in years. As I remember the torque tube is further back like on it is on pre 1/79 FJ45s. That is a challenge on the FJ40s up to 9/72.

 

[Skreddy]

I guess my point is, are you willing to spend money on modifying the driveline based on someone else’s guess, risking paying for it twice?

 

[Living in the Past]

I'm pretty sure it's an early H42 10-spline. The transfer case may be from a three-speed. It looks similar.

I do not believe any H42s ever had a corse spline output shaft. Those were all H41. From the out side really way to tell what a one piece transfer case is. The shifter was the same design up to 4/75. Few lengths were different. 4/75 and later is a simpler design.

 

[Road Hog]

I guess my point is, are you willing to spend money on modifying the driveline based on someone else’s guess, risking paying for it twice?

Thanks,
I'm just getting started so I am kind of bouncing a few options. It looks like the original transfer case is blown, so maybe the tranny is ok. The 4- speed is ok but will still have to be gone over. Lots of questions right now. I'd prefer the 4 speed on the floor, but, weighing just repairing/replacing the old TC. I'm not really sure If this project is feasible, so I'm just working the edges and gathering info.

 

[Road Hog]

I do not believe any H42s ever had a corse spline output shaft. Those were all H41. From the out side really way to tell what a one piece transfer case is. The shifter was the same design up to 4/75. Few lengths were different. 4/75 and later is a simpler design.

 

[Road Hog]

I do not believe any H42s ever had a corse spline output shaft. Those were all H41. From the out side really way to tell what a one piece transfer case is. The shifter was the same design up to 4/75. Few lengths were different. 4/75 and later is a simpler design.

So it looks to be an H41. I believe this came out of my 1972 J55. So would the TC be a 3-speed on this?

 

[pb4ugo]

Regardless of what you do, you're going to have to deal with the driveshafts. You're probably going to need driveshafts with 2 different bolt patterns on each. The female ends should be interchangeable. You need to assemble the driveline to get accurate measurements. You should be able to find a local driveshaft shop to shorten and length the shafts. It's not a big deal. Or possibly find 4 speed shafts.
Its always cheaper to shorten them.

 

[Jdc1]

Regardless of what you do, you're going to have to deal with the driveshafts. You're probably going to need driveshafts with 2 different bolt patterns on each. The female ends should be interchangeable. You need to assemble the driveline to get accurate measurements. You should be able to find a local driveshaft shop to shorten and length the shafts. It's not a big deal. Or possibly find 4 speed shafts.
Its always cheaper to shorten them.

Just had 2 DS shortened and balanced for less than $300.

 

[Skreddy]

You could always do the 4 speed and the adapter to keep the column shift. Be the first Iron Pig with 4 on the tree!

 

[Road Hog]

You could always do the 4 speed and the adapter to keep the column shift. Be the first Iron Pig with 4 on the tree!

I'm confused enough

 

[Living in the Past]

So it looks to be an H41. I believe this came out of my 1972 J55. So would the TC be a 3-speed on this?

That is the input shaft those are all the same on F engines in the 40 series. It also has nothing to do with the transfer case. The output shaft is either 10 spline (three speed and few H41 four speeds) or 16 spline on most four speeds.

 

[Road Hog]

That is the input shaft those are all the same on F engines in the 40 series. It also has nothing to do with the transfer case. The output shaft is either 10 spline (three speed and few H41 four speeds) or 16 spline on most four speeds.

Thanks again, It may be a while until I can tear it down; however, it came out of the 72 so would that increase the odds of it being an H41?

 

[Living in the Past]

Thanks again, It may be a while until I can tear it down; however, it came out of the 72 so would that increase the odds of it being an H41?

If it's a US import it will have a H42. If it"a 72 FJ40 it would have had a three speed from the factory. HJ45 has a four speed in 1972 but not the FJ40. Toyota did not bring in the H42 until 1/74. Some markets had an earlier H41 9/72-9/73. Believe those were coarse spline and a few of the later 41s. But like the H55F five speed Toyota never imported FJ40 to the US with either of those transmissions.

 

[Road Hog]

If it's a US import it will have a H42. If it"a 72 FJ40 it would have had a three speed from the factory. HJ45 has a four speed in 1972 but not the FJ40. Toyota did not bring in the H42 until 1/74. Some markets had an earlier H41 9/72-9/73. Believe those were coarse spline and a few of the later 41s. But like the H55F five speed Toyota never imported FJ40 to the US with either of those transmissions.

I checked out co-pilot to find that Toyota did offer the H41 in the US on some later '72 J55 models. (If you believe AI). I tend to think this may be what I have. The transmission floor cover looks to be original and there's no evidence of a swap. It does look to be about 3 1/2" longer than the three speed out of the '71. But I am curious on whether there may be a driveline out there that fits this factory configuration.

 

[pb4ugo]

So if your dreams come true one way or the other, you better buy a lottery ticket too. I got my finger crossed for ya!