Chrysler 8.25 using D35 driveshaft.

[SanDiegoOverland]

How much lift to make my d35 shaft work with the 8.25?

I'm lifting it anyways, so I thought I'd ask before I went and
bought anything from the junkyard...

I know the the 8.25 is about .75" - 1" longer in the "yokal" area, but
does that translate directly, or is it more like 2-3" of lift?

 

[kastein]

Measure your current driveshaft angle and length, then it's some trigonometry:
starting: old DS angle from ground (theta_1 - measure this with an angle finder as accurately as possible with XJ on level ground); DS length (hypotenuse); driveshaft drop distance from yoke to yoke (opposite - you will calculate this); driveshaft run distance along ground (adjacent - you will calculate this)
ending: new DS angle from ground (theta_2); DS length (same); driveshaft drop distance from yoke to yoke (opposite + lift amount, approximately); driveshaft run distance along ground (adjacent - calculated value from before minus about 1")

We've got theta_1 and hypotenuse, first calculate opposite_1 and adjacent_1:

opposite_1 = hypotenuse * sine(theta_1)
adjacent_1 = hypotenuse * cosine(theta_1)

Now that you have those comes the fun part...

opposite_2 = opposite_1 + lift amount (unknown we want)
adjacent_2 = adjacent_1 - 1"
hypotenuse remains unchanged.
theta_2 is different. We will need it to calculate opposite_2... So first we need to find that from the two knowns, hypotenuse and adjacent:

cosine(theta_2) = (adjacent_1 - 1") / hypotenuse, so:
theta_2 = arccosine((adjacent_1 - 1")/hypotenuse)

Now that we have that, opposite_1, and hypotenuse, we can calculate lift:
sine(theta_2) = opposite_2/hypotenuse
opposite_2 = hypotenuse * sine(theta_2)
lift = (hypotenuse * sine(theta_2)) - opposite_1

I'd combine this all into one big equation... but it'd be really mindbending.

EDIT: What I'd personally do is say "screw all that math", grab a pair of hydro jacks (or a jackstand and a hydro jack), measure the distance from the axle tube to the frame rail on each side, mark the slip yoke where it meets the transfer case seal with tape, then jack the XJ up by the frame till the slip yoke is an inch or so more exposed, then measure from the axle to the rail again and subtract. Pinion angle will screw around with it a little but it'll be pretty accurate.

 

[jeeperjohn]

Measure your current driveshaft angle and length, then it's some trigonometry:
starting: old DS angle from ground (theta_1 - measure this with an angle finder as accurately as possible with XJ on level ground); DS length (hypotenuse); driveshaft drop distance from yoke to yoke (opposite - you will calculate this); driveshaft run distance along ground (adjacent - you will calculate this)
ending: new DS angle from ground (theta_2); DS length (same); driveshaft drop distance from yoke to yoke (opposite + lift amount, approximately); driveshaft run distance along ground (adjacent - calculated value from before minus about 1")

We've got theta_1 and hypotenuse, first calculate opposite_1 and adjacent_1:

opposite_1 = hypotenuse * sine(theta_1)
adjacent_1 = hypotenuse * cosine(theta_1)

Now that you have those comes the fun part...

opposite_2 = opposite_1 + lift amount (unknown we want)
adjacent_2 = adjacent_1 - 1"
hypotenuse remains unchanged.
theta_2 is different. We will need it to calculate opposite_2... So first we need to find that from the two knowns, hypotenuse and adjacent:

cosine(theta_2) = (adjacent_1 - 1") / hypotenuse, so:
theta_2 = arccosine((adjacent_1 - 1")/hypotenuse)

Now that we have that, opposite_1, and hypotenuse, we can calculate lift:
sine(theta_2) = opposite_2/hypotenuse
opposite_2 = hypotenuse * sine(theta_2)
lift = (hypotenuse * sine(theta_2)) - opposite_1

I'd combine this all into one big equation... but it'd be really mindbending.

EDIT: What I'd personally do is say "screw all that math", grab a pair of hydro jacks (or a jackstand and a hydro jack), measure the distance from the axle tube to the frame rail on each side, mark the slip yoke where it meets the transfer case seal with tape, then jack the XJ up by the frame till the slip yoke is an inch or so more exposed, then measure from the axle to the rail again and subtract. Pinion angle will screw around with it a little but it'll be pretty accurate.

I read.....Blah blah blah driveshaft blah blah blah yoke blah blah fun blah blah blah DS blah blah blah mindbending. I guess I need to go back to school and lern me some math

 

[kastein]

Yeah, this is why my engineering friends think I'm a redneck and most of my jeep friends think I'm a nerd :roflmao:

 

[ROBZ95Xj]

How much lift to make my d35 shaft work with the 8.25?

I'm lifting it anyways, so I thought I'd ask before I went and
bought anything from the junkyard...

I know the the 8.25 is about .75" - 1" longer in the "yokal" area, but
does that translate directly, or is it more like 2-3" of lift?

if your running atleast 2" of lift then i say yes, ive ran that setup on a couple of my rigs without issues, also helps with vibes

 

[xjtrailrider]

Well I'm no were near as technical as Karstein LOL!

What I did was put the shaft in after the axle swap, line up the U-joint caps into the yoke and mark the slip yoke at the output shaft seal with a sharpie marker.

Now push the shaft in towards the transfer case a inch and make sure it does not bottom out, now pull the shaft out an inch from your original mark and mark it again. You need a couple of inches or more of contact between the output shaft and slip yoke or you will have issues but you do not want the yoke to bottom out into the T-case.

Remember as the springs compress (flatten out) the axle actually moves away from the T-case but further upward as well so the distance does not change so much. The issue is axle wrap, both from acceleration and braking. That will spit a shaft the quickest. Stay away from lift blocks.

 

[SanDiegoOverland]

Lots of good info here. Didn't come up in my searches.

http://www.naxja.org/forum/showthread.php?t=987766

basically if I want to lift my truck around 5" (which I'm considering) I need to
hack and tap my t-case and get a front driveshaft from an auto xj

I have a 92 4.0l, auto, np231, swapped in 8.25.

supposedly, I'll be all set.

 

[pantherchams]

For reference, I swapped in an 8.25 for a d35 tonight and with about 4" lift my driveshaft is too long. Way too long, literally can't even install it. I have a np242, not sure if that makes a difference.

Ben

 

[ROBZ95Xj]

For reference, I swapped in an 8.25 for a d35 tonight and with about 4" lift my driveshaft is too long. Way too long, literally can't even install it. I have a np242, not sure if that makes a difference.

Ben

year of jeep?

 

[pantherchams]

year of jeep?

1991 4.0 aw4 np242

 

[ROBZ95Xj]

wierd, my last set up on my 93 was 3" lift a d35 drive shaft and yj lipyoke(5/8 longer then xj) and it was perfect, setup on my 95 was 2" lift a d44 with a d35 drive shaft wich was perfect too, both were with 231's though

 

[DrRandy]

I read.....Blah blah blah driveshaft blah blah blah yoke blah blah fun blah blah blah DS blah blah blah mindbending. I guess I need to go back to school and lern me some math

HAHA No Sh&# me too!! Damm i'm dumb!!

 

[pantherchams]

year of jeep?

wierd, my last set up on my 93 was 3" lift a d35 drive shaft and yj lipyoke(5/8 longer then xj) and it was perfect, setup on my 95 was 2" lift a d44 with a d35 drive shaft wich was perfect too, both were with 231's though

Yeah, it sucks. I thought the driveshaft would fit great with the longer yoke of the 8.25. I don't know why it doesn't, seems to me that all the driveshafts are the same for specific tranny/axle combos, and that the TC shouldn't matter.

Ben

 

[cobrasatellite]

no hijack but im running an 8.25 and going to a 35 for a while...i know bad idea...but its a temp thing what should i do about drive shaft i didnt think it would be a issue, should i use the 8.25 or the 35???

 

[kastein]

use the 35 shaft, ESPECIALLY if you're lifted.