Detroits

dcaven

Well-known member
Nov 16, 2007
99
1
Houston, TX
After switing to a CDL transfer case in my 03 Discovery, I am looking at a Detroit locker rear and a Detroit truetrac front. I'm building an expedition type vehicle which has a 2" OME lift and larger than stock but not huge tires. What I'm looking for is for someone to share with me what to expect in terms of performance improvement. They are an expensive upgrade and I'm eager to hear the improvement is dramatic. I've looked online but haven't seen anyone describe the difference on say a scale of 1-10 between Detroit's and stock. Subjective, I know, but would like to get a better sense of people's feelings about them. Thanks.
 

fishEH

Well-known member
Jan 26, 2009
6,927
201
Lake Villa, IL
There's lots of threads going into pros/cons of Detroits, ARB, Ashcroft lockers.
Detroit is nice because its simple and just plain works. Downside is you can't turn it off in sideslope and slippery situations.

Theoretically you'd have a source of on board air on an expedition truck so that shouldn't be a reason for not getting an air locker.
 

dcaven

Well-known member
Nov 16, 2007
99
1
Houston, TX
Thank you. I think I understand the pros and cons from a technical perspective. My question really is am I going to be blown away by the performance improvement versus what I have now? Maybe no way to get a good answer as people's use for their vehicles differ dramatically and experiences vary quite a bit. I'm choking a little on the cost and am trying to decide if the performance gains justify it.
 

p m

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Apr 19, 2004
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Thank you. I think I understand the pros and cons from a technical perspective. My question really is am I going to be blown away by the performance improvement versus what I have now? Maybe no way to get a good answer as people's use for their vehicles differ dramatically and experiences vary quite a bit. I'm choking a little on the cost and am trying to decide if the performance gains justify it.
I badly regretted not using up that 3rd member with a Detroit on Rubicon. Especially when the CV joint blew.
That said... I might have badly regretted using this Detroit on the way to and from Rubicon.
 

Howski

Well-known member
Oct 19, 2009
1,483
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Alabama
It all depends the kind of trails you're going to travel - forest roads or off road parks or somewhere in between? Sliders and diff guards should be on the to-do list well ahead of lockers regardless of the terrain
 

fishEH

Well-known member
Jan 26, 2009
6,927
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Lake Villa, IL
I drove my D1 with Detroit rear / TT front 3000 miles from IL to and through Colorado, then back. Never knew they were there except the lack of wheel spin on the trails.
 

dcaven

Well-known member
Nov 16, 2007
99
1
Houston, TX
Thanks. That is the kind of information I am looking for. I hope to see a big difference off road but very little on.
 

Howski

Well-known member
Oct 19, 2009
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Alabama
On road, the steering wheel returns to center much quicker with the TT up front which takes a little getting used to. Heard the clicking from the Detroit in the rear once in a blue moon only when backing up and turning sharply
 

K-rover

Well-known member
Jan 15, 2010
2,163
62
Raleigh, NC
I just recently installed F+R air lockers and regeared to 4.11's.. Its a game changer for sure off road! The gearing is what is really noticeable, both on and off highway.

Remember that the TT is a limited slip and not a true "locker" such as a Detroit or air locker. So performance offroad is slightly better, but not as good as true locker.
 

dcaven

Well-known member
Nov 16, 2007
99
1
Houston, TX
Have the 4.11's crushed your gas mileage? I understand that is a relative question as Discoveries really like gas anyway. Just curious.
 

K-rover

Well-known member
Jan 15, 2010
2,163
62
Raleigh, NC
Have the 4.11's crushed your gas mileage? I understand that is a relative question as Discoveries really like gas anyway. Just curious.

I'm running 34's going to 35's so the gearing was needed. I'm currently running at 2200-2400 rpm at 65ish mph where as on stock gearing I was at 1800 rpm at the same speeds. So yeah gas mileage has suffered a bit, but I only really drive the truck to and from the trails. Its not my daily driver.
The biggest thing with the gearing on the highway is the trans isn't searching for gears while climbing hills. Off road 1st gear low range is truly a crawl gear now.
 

fishEH

Well-known member
Jan 26, 2009
6,927
201
Lake Villa, IL
Why bad? It was awesome! With the rear Detroit it might have been way too easy.

That's actually a good point. I went selectable lockers on my other truck because I wanted a challenge, along with other reasons. My truck was setup with 35's and long travel suspension so it was more fun to climb obstacles without lockers.
But on the other hand I was very happy to have a Detroit in CO. I was driving a new to me 94 D1 Manual trans. My skills with a manual were a little rusty and I was glad I didn't have to think about turning lockers on/off, or losing traction/momentum on a steep hill or tight turn, then trying to turn the locker on, then restarting.
 

p m

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But on the other hand I was very happy to have a Detroit in CO. I was driving a new to me 94 D1 Manual trans. My skills with a manual were a little rusty and I was glad I didn't have to think about turning lockers on/off, or losing traction/momentum on a steep hill or tight turn, then trying to turn the locker on, then restarting.
My Rubicon observation of several dozens of jeeps: most of them run super-low gearing, and either a hand throttle on the stick or simply bumped up idle. They practically don't use gas pedal through most "regular" sections.
You know that probably 90% of the time you run the truck close to 1500 rpm - so setting it to about a thousand by that knob on the throttle cable could have saved you some grief with three pedals.
 

squirt

Well-known member
Nov 13, 2008
824
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Los Angeles
Thanks. That is the kind of information I am looking for. I hope to see a big difference off road but very little on.

If this is your primary goal, get air lockers. They do exactly what you're asking for.

I went with Ashcroft lockers front & rear earlier this year, and at this point, the truck is more capable than I am. (not necessarily a good thing) My experience is that the OE traction control on my D2 did a pretty good job, but in a situation where you've got 1 wheel on each axle slipping, you'll still get stuck, end up rocking back and forth, spinning wheels, etc. I found myself encountering this pretty often, due to a combination of trail difficulty and inexperience. Air lockers make these situations a non-issue.

Naturally, the on-road experience is the same as having open diffs.
 

jymmiejamz

Well-known member
Dec 5, 2004
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Los Angeles, Ca
I just put 4:11 gears with a TT/Detroit combo in my D90. The only noticeable difference, as noted, is it always wants to return to center and more so than with factory steering geometry. The steering is a little stiffer at speed, but I don't think it is at parking lot speeds.
 

Mongo

Well-known member
Apr 19, 2004
5,731
2
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Ashcroft air lockers are your best bet

if $$$ is a question then a TT/Detriot is a very vialbe option
 

finnarne

Member
Feb 4, 2015
9
0
Norway
I have a DetroitLocker/TrueTrac combination on my Disco1. Just fit and forget. I often forget the locker(s) are in place, until someone else with a similar truck has difficulties on obstacles i pass with ease.