• Want to add an app icon for this forum to your mobile device's home screen? Check out this thread to see how.
  • Have an event you want to share? Check out the new forum event calendar and how-to use it in this thread here.
  • To both new members and existing members, please read this thread about posting your topics in the correct sub-forum. It makes my job (and my life) a lot easier!

Two tummy tuck questions relating to transmission and driveshaft

Thunder Mass

Member
Supporting Member
Joined
Sep 16, 2018
Messages
92
Location
Washington
I'm trying to plan out my upcoming build on my '05 LJ; assuming I can fund it. And while I'm not planning on doing a tummy tuck at this point, it definitely is something I'd like to do in the future. Which is why I'd like to make sure that the first part of my build won't be wasteful in the future.

So the first is the transmission. I've got the 6 speed manual NSG370. It pops out of first gear if I don't hold it in place, seemed to start after my father got rear ended before I bought it from him. But, it sounds like a somewhat common thing to happen with those trannys too. Anyway, at some time, I'd like to get that fixed. Not high priority for me, though. I thought that you had to drop the transmission to do a tummy tuck, so I figured I'd do them together, to save labor cost. But after looking at it some more, it doesn't look like the tranny is involved at all. Is this true? That way, I can do them independently. Or rather, maybe you have to remove the transfer case to remove the transmission?

Second is the driveshaft. I was hoping to get away with not needing a new driveshaft even with a 4" short arm, being that I have an LJ, but I think I'll just go ahead and do it to be safe. And a SYE, of course. But I gotta wonder, if I do the tummy tuck later on, will the driveshaft I got for the 4" lift still work? I'm hoping so, especially with LJs seeming to be more forgiving in that area. Or, am I just over thinking it?

Thanks.
 

Chris

Administrator
Staff Member
Joined
Sep 28, 2015
Messages
39,763
Location
Salem, Oregon
The transmission doesn't have to be dropped to do a tummy tuck, not even close. Nothing happens to the transmission at all other than having to support it while you remove the skid plate. The transfer case doesn't have to be remove either. All you're doing is bolting on a new, lower profile skid plate, that's it.

You WILL need a new driveshaft and SYE (assuming yours isn't a Rubicon), as 4" of lift plus a tummy tuck will equate to around 6-7" of lift in regards to how the driveline angles will be after the tuck. A tummy tuck alone is the equivalent of adding 2-3" of lift in terms of the driveline angle.

The driveshaft you get for 4" of lift will likely not work for the tummy tuck. Do the smart thing and order the driveshaft AFTER you add the tummy tuck and take the measurements. Ordering it beforehand is just guessing, and could end up working, but also could not end up working.
 
OP
Thunder Mass

Thunder Mass

Member
Supporting Member
Joined
Sep 16, 2018
Messages
92
Location
Washington
Yeah, not sure how I got it in my head that a tummy tuck affected the tranny.

So, the transfer case doesn't get removed, but it is still pushed up higher into the body, correct? That's how you get equivalent of 2-3" of lift on the driveline.

That's definitely a bummer. Cuz I'm trying to see if I can afford lockers at the same time. And it's my daily driver, so the less time it spends in the shop, the better.

Only other thing though, I might already be getting most everything I need already. From the Official Tummy Tuck thread:
Motor Mount Lift (MML)
Rear upper adjustable control arms
Rear track bar relocation bracket


Already come with the Currie lift
_
Double Cardan Driveshaft
Slip Yoke Eliminator (SYE)


Already going to get anyway (Not a Rubi, BTW)
_
Rear shock relocation brackets
Body Lift


Are cheap enough
_
Spring perch modifications

Shouldn't need
_
Transfer case bracket
Skids


Only somewhat expensive parts to add to the cost.
_
Exhaust mod

Unless I have to do this too.

So, maybe it won't be TOO much more expensive to do it, but I might have to forget about the lockers. Or, maybe not do the tummy tuck. I'm planning on the 4" Currie and either 33s or 35s. All depends on what the prices will be at the Truck and Jeep fest in Puyallup, WA. Sounds like things will be fairly cheap. Maybe.

Every time I think I have it figured out, something else comes up. But, at least I know now. Thank you so much.
 

Chris

Administrator
Staff Member
Joined
Sep 28, 2015
Messages
39,763
Location
Salem, Oregon
So, the transfer case doesn't get removed, but it is still pushed up higher into the body, correct? That's how you get equivalent of 2-3" of lift on the driveline.
Correct. You're pushing the transfer case up into the body / tunnel around 2-4" (depending on which skid plate you use), and that equates to a much steeper driveshaft angle, hence you have to rotate your rear pinion up even further. Be prepared to relocate your spring perches in the rear after this, as your rear springs will likely be bowed substantially (mine were).


That's definitely a bummer. Cuz I'm trying to see if I can afford lockers at the same time. And it's my daily driver, so the less time it spends in the shop, the better.
A tummy tuck is a cascading project, that's for sure. You'll also need to plan to have your exhaust slightly modified, as after the tummy tuck, it's bound to hit things (mine did quite a bit!).

So, maybe it won't be TOO much more expensive to do it, but I might have to forget about the lockers. Or, maybe not do the tummy tuck. I'm planning on the 4" Currie and either 33s or 35s. All depends on what the prices will be at the Truck and Jeep fest in Puyallup, WA. Sounds like things will be fairly cheap. Maybe.

Every time I think I have it figured out, something else comes up. But, at least I know now. Thank you so much.
Believe me, it's best to go into this thinking you're going to spend a lot more than you think. I can almost guarantee you'll need slight exhaust modifications, and while you technically won't need to relocate your rear spring perches, your rear springs will be bowed so much from the equivalent of 7" of lift, that if you flex out the rear suspension, you'll likely loose a spring (i.e. it will pop out under full droop).

I'm not trying to discourage you, I'm just saying that it's one of those projects that will likely end up being more money than you think it will, so plan for that. It certainly took quite a bit to get mine right!
 

LukesfirstJeep

TJ Enthusiast
Joined
Aug 2, 2018
Messages
385
Location
Central PA
Do you need 4" of lift? I did a simple 3" Zone lift on my LJ. Zone uses a spacer between frame and skid to drop the trans a little. I have no vibration up to 80+ MPH. I haven't gone faster. With 3" of lift, I didn't need a SYE, new control arms, MML, or other mods. Something to consider. Zone make a combo lift, 3" suspension and 1" body if you need 4".
 
OP
Thunder Mass

Thunder Mass

Member
Supporting Member
Joined
Sep 16, 2018
Messages
92
Location
Washington
Correct. You're pushing the transfer case up into the body / tunnel around 2-4" (depending on which skid plate you use), and that equates to a much steeper driveshaft angle, hence you have to rotate your rear pinion up even further. Be prepared to relocate your spring perches in the rear after this, as your rear springs will likely be bowed substantially (mine were).




A tummy tuck is a cascading project, that's for sure. You'll also need to plan to have your exhaust slightly modified, as after the tummy tuck, it's bound to hit things (mine did quite a bit!).



Believe me, it's best to go into this thinking you're going to spend a lot more than you think. I can almost guarantee you'll need slight exhaust modifications, and while you technically won't need to relocate your rear spring perches, your rear springs will be bowed so much from the equivalent of 7" of lift, that if you flex out the rear suspension, you'll likely loose a spring (i.e. it will pop out under full droop).

I'm not trying to discourage you, I'm just saying that it's one of those projects that will likely end up being more money than you think it will, so plan for that. It certainly took quite a bit to get mine right!
I was assuming I wouldn't need the spring perch, as it was said in the tummy tuck thread that it was only necessary on high lifts. Is a 4" short arm considered high enough?

With the exhaust, would it be some kind of custom work, or would an aftermarket exhaust work? I'm guessing it's the former, and whatever aftermarket exhaust I'd get would have similar issues.

It's only slightly discouraging, but I'd rather be discouraged in the planning phase than do it, and find out I'll need to drop more money into it. I'm already looking at a little over $10K as it is.
 
OP
Thunder Mass

Thunder Mass

Member
Supporting Member
Joined
Sep 16, 2018
Messages
92
Location
Washington
Do you need 4" of lift? I did a simple 3" Zone lift on my LJ. Zone uses a spacer between frame and skid to drop the trans a little. I have no vibration up to 80+ MPH. I haven't gone faster. With 3" of lift, I didn't need a SYE, new control arms, MML, or other mods. Something to consider. Zone make a combo lift, 3" suspension and 1" body if you need 4".
I did look at the Zone lifts a few years ago, but I've been pretty set on the Currie for some time; unless I went with long arms. Plus I only wanna do a body lift to support a tummy tuck or 35s, if I do 33s with no tummy tuck I'll just do the 4" and skip the body lift. And, I don't wanna drop the transfer case any lower than it is.
 

Chris

Administrator
Staff Member
Joined
Sep 28, 2015
Messages
39,763
Location
Salem, Oregon
I was assuming I wouldn't need the spring perch, as it was said in the tummy tuck thread that it was only necessary on high lifts. Is a 4" short arm considered high enough?

With the exhaust, would it be some kind of custom work, or would an aftermarket exhaust work? I'm guessing it's the former, and whatever aftermarket exhaust I'd get would have similar issues.

It's only slightly discouraging, but I'd rather be discouraged in the planning phase than do it, and find out I'll need to drop more money into it. I'm already looking at a little over $10K as it is.
A 4" short arm lift PLUS a tummy tuck (which adds another 3" or so of lift to the driveline), and you're talking about 7" of lift, maybe even a bit more. So yes, your spring perches will be way off from where they should be.

The exhaust work is easy. Just take it to any shop who knows how to weld (or any exhaust shop) and they'll just have to clearance certain areas of it. It's not hard by any means, you just have to know how to weld and have some extra exhaust piping on hand.

10k sounds about right to be honest. It adds up fast, especially when you're using quality parts. It's easy to see how someone can spend 20k without even blinking.
 
OP
Thunder Mass

Thunder Mass

Member
Supporting Member
Joined
Sep 16, 2018
Messages
92
Location
Washington
A 4" short arm lift PLUS a tummy tuck (which adds another 3" or so of lift to the driveline), and you're talking about 7" of lift, maybe even a bit more. So yes, your spring perches will be way off from where they should be.

The exhaust work is easy. Just take it to any shop who knows how to weld (or any exhaust shop) and they'll just have to clearance certain areas of it. It's not hard by any means, you just have to know how to weld and have some extra exhaust piping on hand.

10k sounds about right to be honest. It adds up fast, especially when you're using quality parts. It's easy to see how someone can spend 20k without even blinking.
I understand how that gets to be about 7" of lift in regards to the driveshaft, but I didn't think that it would look that way to the suspension. I figured it was still 4" as far as the springs were concerned.

So, I'd like to do a cat-back exhaust someday as well. Also not high priority. That said, would the area being cut be a part of the the new exhaust, or the older part that remains? Because with the whole theme of this thread, I'd like to only do work once if I can help it.

Yeah, Currie lift, Revolution gears and shafts, Black Magic brakes. Maybe a ZJ steering swap, but likely Currie. Either Rancho or Bilstein shocks, probably Pro Comp wheels and either BFG or Dick Cepek tires. That's why I gotta wait for the big yearly sale.
 

tworley

TJ Addict
Supporting Member
Ride of the Month Winner
Joined
May 23, 2018
Messages
2,594
Location
Morrison, CO
Total lift seen by transfercase = spring lift + your skid plate lift (tuck).
 
OP
Thunder Mass

Thunder Mass

Member
Supporting Member
Joined
Sep 16, 2018
Messages
92
Location
Washington
Total lift seen by transfercase = spring lift + your skid plate lift (tuck).
Right, that makes sense. I just didn't think that my springs would care if I did a tummy tuck or not.



Hmm, after looking into the spring perch a little, while they're not expensive they need to be welded on. Not to sound lazy or cheap, but that sounds like it'll add a lot more to the labor costs.

And while we're at it, I've read to not worry about the front drive shaft length with a lift. But with a tummy tuck, does that make it more of an issue?

And not to hijack my own thread, but while it looks like the tummy tuck won't be TOO much more expensive compared to, say, lockers. That said, which one would be more valuable? I guess that's a poor question, really, cuz it all depends on what and where I wheel. I dunno, it's my DD, so I don't put it in too risky of spots. I had one time needed more clearance, but the lift and tires would fix that. And one time I really needed more traction, though I dunno if lockers would have helped.
 

Chris

Administrator
Staff Member
Joined
Sep 28, 2015
Messages
39,763
Location
Salem, Oregon
I understand how that gets to be about 7" of lift in regards to the driveshaft, but I didn't think that it would look that way to the suspension. I figured it was still 4" as far as the springs were concerned.

So, I'd like to do a cat-back exhaust someday as well. Also not high priority. That said, would the area being cut be a part of the the new exhaust, or the older part that remains? Because with the whole theme of this thread, I'd like to only do work once if I can help it.

Yeah, Currie lift, Revolution gears and shafts, Black Magic brakes. Maybe a ZJ steering swap, but likely Currie. Either Rancho or Bilstein shocks, probably Pro Comp wheels and either BFG or Dick Cepek tires. That's why I gotta wait for the big yearly sale.
It will look like that to the suspension.

When you lift it 4", then add that tummy tuck (which is the equivalent of another 3" or so), what do you think happens to your rear pinion angle? You have to rotate it up even more (for the tummy tuck). What do you think then happens to your spring perches? They move back even further, therefore bowing the springs.

The exhaust doesn't need to be cut off entirely. In my case I had to relocate some hangers on the exhaust, simple stuff but worth mentioning.
 
OP
Thunder Mass

Thunder Mass

Member
Supporting Member
Joined
Sep 16, 2018
Messages
92
Location
Washington
It will look like that to the suspension.

When you lift it 4", then add that tummy tuck (which is the equivalent of another 3" or so), what do you think happens to your rear pinion angle? You have to rotate it up even more (for the tummy tuck). What do you think then happens to your spring perches? They move back even further, therefore bowing the springs.

The exhaust doesn't need to be cut off entirely. In my case I had to relocate some hangers on the exhaust, simple stuff but worth mentioning.

Makes sense, I just figured that the longer driveshaft would negate that.

Okay, so it really shouldn't matter when (or if) I do an aftermarket exhaust.
 

Chris

Administrator
Staff Member
Joined
Sep 28, 2015
Messages
39,763
Location
Salem, Oregon
Makes sense, I just figured that the longer driveshaft would negate that.

Okay, so it really shouldn't matter when (or if) I do an aftermarket exhaust.
No, the exhaust won't really matter.

Like I said, you can get by without relocating the spring perches, you'll just have really bowed rear springs, and if you decided to do any off-roading, you'll definitely be more at risk of losing a spring if the axle droops enough.

Rear spring perch relocation brackets are like $100 or so I believe, and cutting the old ones off to weld the new ones on isn't difficult. Maybe a few hours of labor tops.
 
OP
Thunder Mass

Thunder Mass

Member
Supporting Member
Joined
Sep 16, 2018
Messages
92
Location
Washington
No, the exhaust won't really matter.

Like I said, you can get by without relocating the spring perches, you'll just have really bowed rear springs, and if you decided to do any off-roading, you'll definitely be more at risk of losing a spring if the axle droops enough.

Rear spring perch relocation brackets are like $100 or so I believe, and cutting the old ones off to weld the new ones on isn't difficult. Maybe a few hours of labor tops.
Okay, the (aftermarket) exhaust will wait then.

If I do a tummy tuck, I'd rather do it right and do the spring perches. Just to play it safe. Thanks.
 

jjvw

0-60 in 18 seconds
Supporting Member
Joined
Feb 17, 2018
Messages
7,627
Location
Colorado, USA
Bowed springs has little to do with why the upper spring seats get moved.

The higher the lift, the higher the tuck, the more the pinion gets raised. The more the pinion is raised, the less the bump stops line up. The reason the spring seats get moved is to get the bump stops to line up again.
 
  • Like
Reactions: billiebob
OP
Thunder Mass

Thunder Mass

Member
Supporting Member
Joined
Sep 16, 2018
Messages
92
Location
Washington
I won't be doing this until the very end of May at the earliest, probably more like June. April is important only because I should be able to get a lot of the parts cheap then. I will be doing research until the day everything gets installed, and if I'm not ready, I'll wait.
 

TurboTJ

TJ Enthusiast
Supporting Member
Joined
Jan 5, 2019
Messages
237
Location
Walnut Creek, CA
I just did a tummy tuck “light” by installing a Barnes skidplate. It lifts the transfer case 3/4 inch and increases the ground clearance an inch or more. It is not like the OEM shovel that seems to scoop up dirt. The increase in ground clearance isn’t much but the surface is flat so it should skid over things better. Even with just the 3/4 inch transfer case lift the driveline angles are noticeably steeper but with a 2 inch lift and single Cardan I still have no vibration.
 
  • Like
Reactions: lindsey97