SYE, Gears, Lockers, & Shafts: What's First?

[Breto31]

I've made it to the point where the next list of projects are (what I consider) major ones - and I'm hoping I can get some input on where to start.... I know that I definitely want to re-gear to 4.56 or 4.88 (I'm on 33's), and put in some type of locker or limited-slip (at least in the back, but possibly front too). Might as well do those at the same time.... Depending on the locker choice, I would potentially upgrade to Chromoly axle shafts. I've got the Dana 30/35, and I know the stock shafts have their own set of issues.

Regarding the lockers: I don't want something that is locked all the time, and I don't want to spend a ton of money for e-lockers, or air lockers. Based on that, it seems like a limited-slip TruTrac is a great way to go. They don't seem to be as efficient as an actual locker, but I'm not rock crawling and my wheeling is fairly light - a few times per year, mostly mud/forest roads in the Southeast..... If I go with the limited-slip, am I correct in saying that I SHOULDN'T upgrade to chromoly shafts? Is the TruTrac a sufficient option?

Regarding the gearing: I have a 4" suspension lift, on 33's, 6-speed manual. My stock 3.73's are fine overall, but they leave something to be desired on the highway - and I figure if I'm putting in a locker or LS, I might as well have the gearing done while I'm there. My jeep will run 70-75 on the highway, but it definitely loses power on the up-hill. Do you guys recommend 4.56 or 4.88? Is there a preferred brand that has quality reviews, but won't break the bank? Yukon and Motive Gear seem to be about the same price.

Regarding the SYE: I still don't have a SYE installed, and I know next-to-nothing about them. I have a t-case drop, and it's not been much of a problem overall, but I've seen the drawbacks on some of the more technical trails I've ran. I'm considering having a SYE put in as well to get rid of the t-case drop. The Tom Wood's website recommends the Teraflex Extreme Short 231 kit. This may a silly question, but will I need to get a new driveshaft along with a SYE kit, or does it bolt right into the existing driveshaft?

I would appreciate any feedback/input!

 

[DUB]

I am curious to see what other members have to say about the detroit, the way you asked it anyway.. I am in the same type of situation and considering that.

What I understand (have read here), not necessary to go with axle upgrade on 33's and not crawling. Also, I have the same setup as you and no SYE or case drop. I did the MML and BL. This has been a great solution for me and saves a ton of coin.

 

[Breto31]

I am curious to see what other members have to say about the detroit, the way you asked it anyway.. I am in the same type of situation and considering that.

What I understand (have read here), not necessary to go with axle upgrade on 33's and not crawling. Also, I have the same setup as you and no SYE or case drop. I did the MML and BL. This has been a great solution for me and saves a ton of coin.

I actually DO have the t-case drop. It’s not really a problem until it is…. I don’t understand the MML/BL scenario. I feel like I should, but I don’t. What exactly does that accomplish? Honestly, I don’t think I truly understand what the SYE does aside from eliminates the case drop. Does the MML/BL essentially do the same thing as a SYE?

 

[machoheadgames]

IF you will be staying on 33's, I'd go with 4.56. If there's any chance of 35's, go with 4.88 for the 6-speed. If there's any chance of going to an AX15 if your6 speed craps the bed eventually, go with the lower ratio (4.88 for 33's, etc).

You don't want a locker because you have the stock Dana 35. Really building a stock dana 35 for 33's is not a great idea, although it can live a while if it's babied. The TrueTrac would get rid of the spider gears at least which are a known weak point. You can upgrade to slightly stronger 1541H shafts (still 27 spline), but they're still not super strong.

Chromoly or not is a function of what axle you have. You don't want chromoly in a Dana 35 due to the roller bearing wheel bearing design that rolls straight on the shaft and not a pressed on race.

If it were me, I'd go in the order of SYE, gears/carrier, then shafts. SYE gets the driveshaft issues fixed first, which you can then apply higher speeds to via the new gears. Shafts can be installed anytime. The only thing you lose by installing shafts later than the gears is about 30 minutes of time and some gear oil because you have to drain the oil to remove and install Dana 35 shafts due to the c-clip design.

 

[machoheadgames]

I actually DO have the t-case drop. It’s not really a problem until it is…. I don’t understand the MML/BL scenario. I feel like I should, but I don’t. What exactly does that accomplish? Honestly, I don’t think I truly understand what the SYE does aside from eliminates the case drop. Does the MML/BL essentially do the same thing as a SYE?

The SYE changes the output of the transfer case from a slip yoke to a fixed yoke. To go along with the SYE, you get a new stronger double cardan (effectively a CV "constant velocity") style driveshaft that has the slip joint built into the body of the driveshaft. The benefit to this is being able to fix your driveline angles to prevent vibration from lifting too tall.

 

[DUB]

By lifting the engine you will put the driveline back to a much closer angle. When you do a body lift you get the body and engine back to the where they started, i.e. you don't need to raise the fan shroud, etc.

 

[Breto31]

The SYE changes the output of the transfer case from a slip yoke to a fixed yoke. To go along with the SYE, you get a new stronger double cardan (effectively a CV "constant velocity") style driveshaft that has the slip joint built into the body of the driveshaft. The benefit to this is being able to fix your driveline angles to prevent vibration from lifting too tall.

So this kit would come with everything that I would need to have the SYE installed, right? There’s no additional parts needed?

 

[machoheadgames]

So this kit would come with everything that I would need to have the SYE installed, right? There’s no additional parts needed?

Not sure if you meant to post a link to a kit or something, but a traditional SYE kit will require you to measure and order for a new driveshaft (double cardan) after you're done installing the SYE. You can order one from Adams, Tom Wood, Tatton's, Denny's, etc.

You can order an SYE and driveshaft bundle from Adam's or Tom Wood's, but they'll still want to know a measurements after you're done installing before they'll want to build you the shaft, that way they get it right first try and don't have something affecting the measurement due to variables.

 

[Breto31]

Not sure if you meant to post a link to a kit or something, but a traditional SYE kit will require you to measure and order for a new driveshaft (double cardan) after you're done installing the SYE. You can order one from Adams, Tom Wood, Tatton's, Denny's, etc.

You can order an SYE and driveshaft bundle from Adam's or Tom Wood's, but they'll still want to know a measurements after you're done installing before they'll want to build you the shaft, that way they get it right first try and don't have something affecting the measurement due to variables.

Sorry - this is the link I meant to post.

https://teraflex.com/tj-np231-extreme-short-shaft-kit.html

 

[machoheadgames]

Sorry - this is the link I meant to post.

https://teraflex.com/tj-np231-extreme-short-shaft-kit.html

You would need to measure for and order a driveshaft to go along with that once installed.

Also, if you like a calibrated speedometer, you will want some form of speedometer correction device. The new speed sensor that SYE converts you to is non adjustable like the speedometer gear setup it is replacing. It is calibrated for somewhere around a 31-33" tire and 4.10s.

 

[Breto31]

You would need to measure for and order a driveshaft to go along with that once installed.

Also, if you like a calibrated speedometer, you will want some form of speedometer correction device. The new speed sensor that SYE converts you to is non adjustable like the speedometer gear setup it is replacing. It is calibrated for somewhere around a 31-33" tire and 4.10s.

Good to know that I’d need the kit + a driveshaft. Thanks!

I don’t anticipate 35’s or any axle swaps, so it sounds like 4.56 gears and TruTracs, are reasonable upgrade given my setup.

EDIT: is there any specific brands to avoid when shopping for gears, or are they all pretty comparable?

 

[Duck Doctor]

Good to know that I’d need the kit + a driveshaft. Thanks!

I don’t anticipate 35’s or any axle swaps, so it sounds like 4.56 gears and TruTracs, are reasonable upgrade given my setup.

EDIT: is there any specific brands to avoid when shopping for gears, or are they all pretty comparable?

I’d go with Dana/Spicer gears. Make sure to have the shop installing the gears/limited slip source all the parts so the work has a full warranty.

 

[macleanflood]

I did my SYE first... mostly because I had to do the clutch and I had to cut off the bolts and through the 1" square tube the PO used as a spacer. Figured since I already had it out...

-Mac

 

[roverhi]

The SYE with Cardon drive shaft also requires a way to change the angle of the diff. input shaft. A regular drive shaft universal joint needs the diff. output shaft parallel to the trans. output shaft. The Cardan UJ needs the output shaft tilted up pointing at the trans. output shaft. A set of adjustable upper control arms is the minimal fix for this. Most seem to highly recommend both adjustable control arms, upper and lower, to keep the rear axle centered in the wheel well.

 

[LONGJP2]

Does the MML/BL essentially do the same thing as a SYE?

The MML does the same thing as a TC drop.
The BL provides more clearance, if needed and/or wanted.

 

[machoheadgames]

Good to know that I’d need the kit + a driveshaft. Thanks!

I don’t anticipate 35’s or any axle swaps, so it sounds like 4.56 gears and TruTracs, are reasonable upgrade given my setup.

EDIT: is there any specific brands to avoid when shopping for gears, or are they all pretty comparable?

I’d do Dana spicer or Revolution. I’m pretty sure either are available right now.

 

[Breto31]

The SYE with Cardon drive shaft also requires a way to change the angle of the diff. input shaft. A regular drive shaft universal joint needs the diff. output shaft parallel to the trans. output shaft. The Cardan UJ needs the output shaft tilted up pointing at the trans. output shaft. A set of adjustable upper control arms is the minimal fix for this. Most seem to highly recommend both adjustable control arms, upper and lower, to keep the rear axle centered in the wheel well.

I do already have adjustable upper/lower control arms, so that’s one less thing to do.

 

[LONGJP2]

As you lift the Jeep, the u-joints exceed their operating range.
An SYE (and longer driveshaft), TC drop, & MML all help to lessen the angle.
A DC driveshaft allows even more usable angle at the trans. output.

 

[Irun]

While it is not the same as a locker, a Detroit True Trac can be advantageous in many situations. Largely, in cases where you're not going to be carrying a wheel in the air. I currently run one in the front, and know people who run them front and rear. As long as you know what you're getting, and how you'll use it, they are a solid option.

FWIW, here's a little video (not mine) that shows a limited slip in use with a little brake application. That said, there's a difference between moving a vehicle on level ground when applying braking, versus moving a Jeep up and over a steep obstacle.

 

[Breto31]

Couple of questions about the TrueTracs that I should probably understand, but don't.... These are fairly big purchases, so I just want to make sure I don't order something incorrectly.

Am I understanding correctly that the Dana 30 front and Dana 35 rear diffs get DIFFERENT model number TrueTracs? Or do both differentials get the exact same model? I found these on Summit - https://www.summitracing.com/parts/etn-912a585 and https://www.summitracing.com/parts/etn-912a569..... The Dana 30 front one says recommended for 3.73 and numerically higher gears (which would be what I currently have, and 4.56 I plan to put in). The Dana 35 rear says recommended for 3.54 and numerically higher ratios, which would also be my current setup, or the 4.56 I plan to go to.

Regarding gears, does anyone know anything about this Yukon 4.56 kit or have any experience with Yukon? From what I've read, Yukon gears have a good reputation. Revolution is sold out of 4.56 kits for a Dana 30/Dana 35. https://www.yukongear.com/shop/ygk005