3.73 vs 4.10

[WesChapman]

2005 Renny current gear set 3.73 open, 93k miles

Rear end needs a rebuild, budget is limited, Primary use is daily 96 mile round trip commute, mostly mountain roads, average round trip speed is 38mph. Someday I would like to use the Jeep for fun and not just commuting.
Options are:
1.rebuild to stock (3.73, open) cheapest
2.rebuild w 3.73 & trac-loc slightly less cheap
3.rebuild w 4.10 & trac-loc least cheap AND can't afford to do front at same time.

Option 1 gets the Jeep functional, but doesn't add to off road capability
Option 2 gets the Jeep functional, offers a bit better off roadability
Option 3 gets the Jeep functional, should improve performance, but lose 4x4 capability until $$$ saved for front axle.

I like option 3, but worry that D30a 4.10 gear sets are in limited supply and could possibly be unavailable in the future.
If I temporarily run mis matched gears, will I have to drop the front drive shaft or could I leave it connected but not use 4x4. (I have part time only t-case) I'm the only one driving the Jeep so I'm not worried about accidental t-case engagement. Does the Jeep t-case have some sort of syncho for on the fly engagement?

Thoughts?

Thanks

 

[ridenby]

If you go with 4.10,the drive shaft will need to be removed until the front is changed also.

 

[kjweston]

Don't waste your money on trash loc

 

[SurfGuitar141]

Don't waste your money on trash loc

That's typical internet hype....don't throw a statement like that out, and not back it up with real world facts as to "WHY" you think it's trash...

Got documentation on Trac-Loc failures.....post it...
Got a friend that had Trac-Loc fail on him/her....get them on here to tell the story.....

Offer the OP other real world options, there's other limited slip differentials on the market that fit the Chrysler 8.25, and Dana 30 axles.....


Sorry Kjweston, but I'm loosing my patients with "Seagull" posts......

Seagull post.......when someone flies into an established thread, ***** all over it and flies away leaving no real redeeming information to help those seeking knowledge on any given subject.....

 

[HoosierJeeper]

If your tires are near stock size (and aren't planning to upgrade), keep the 3.73's.

 

[rockymountain]

If your tires are near stock size (and aren't planning to upgrade), keep the 3.73's.

I totally agree with this. If you have stock tires with no lift stay with your 3.73's. If you plan on getting bigger tires as in diameter then look into the 4.10's. As far as trac-lock, it may help a little. Its definitely better than an open diff, but I don't know how much better. and it is inevitable that trac-lock one day just wears out. You can weigh that against how long you'll have the thing.

 

[AlexKJ]

If your tires are near stock size (and aren't planning to upgrade), keep the 3.73's.

Beg to differ... If I have the chance to going 4.10:1 I'll do it in a breeze... even with stock tires...

Here is hilly terrain and heavy traffic (stop & go million times) is killing my gas... And there isn't so much difference between 3.73 & 45RFE vs 4.10 & 42RLE

The ratios for the 42RLE are:
First -- 2.84:1
Second -- 1.57:1
Third -- 1.00:1
OD -- 0.69:1
Reverse -- 2.21:1

The 45RFE ratios are as follows:
First -- 3.00:1
Second -- 1.67:1
Alt Second -- 1.50:1
Third -- 1.00:1
OD -- 0.75:1
Reverse -- 3.00:1

Crawl Ratio:
28.81 (42RLE - 3.73)
30.44 (45RFE - 3.73)
31.67 (42RLE - 4.10)

Speed Comparison

Trans    RPM     Gear   Transfer    Diff   Tire Height   Speed (mph)
42RLE    2000    2.84       1       4.10     28.95"       14.8
45RFE    2000    3.00       1       3.73     28.95"       15.4

42RLE    2000    0.69       1       4.10     28.95"       60.9
45RFE    2000    0.75       1       3.73     28.95"       61.6

Not too different... aren't they?

 

[rockymountain]

Speed Comparison

Trans    RPM     Gear   Transfer    Diff   Tire Height   Speed (mph)
42RLE    2000    2.84       1       4.10     28.95"       14.8
45RFE    2000    3.00       1       3.73     28.95"       15.4

42RLE    2000    0.69       1       4.10     28.95"       60.9
45RFE    2000    0.75       1       3.73     28.95"       61.6

Not too different... aren't they?

Good data there, but what about comparing just the 42 with 3.73's vs 4.10's. We aren't talking about swapping the transmission. The OP states he has an '05 so he has a 42RLE. Or am I missing something in my caffeine clouded state.

 

[AlexKJ]

Good data there, but what about comparing just the 42 with 3.73's vs 4.10's. We aren't talking about swapping the transmission. The OP states he has an '05 so he has a 42RLE. Or am I missing something in my caffeine clouded state.

No, I do not suggest change of transmission...

I'm only saying that the 45RFE & 3.73 it's the original automatic transmission of a 3.7L 2002 KJ... So, it wouldn't be sooo heretic have a 3.7 with 42RLE, standard tires and 4.10 b/c the resultant numbers aren't too different... capisci?

 

[rockymountain]

Actually the 45 was available up to about mid April of '03. I used to have an '03 built in the first week of April of '03 and it kicked the 42RLE's ace up and down and sideways. I soooooooo miss that setup.

 

[kb0nly]

Actually the 45 was available up to about mid April of '03. I used to have an '03 built in the first week of April of '03 and it kicked the 42RLE's ace up and down and sideways. I soooooooo miss that setup.

Not so... I have a 03' built earlier than April and i have a 42RLE trans... So the rule doesnt always apply.

I have crawled under a dozen 03's now, i haven't found a 45RFE yet, i'm starting to think that April date is a bunch of whooey...

 

[rockymountain]

Not so... I have a 03' built earlier than April and i have a 42RLE trans... So the rule doesnt always apply.

I have crawled under a dozen 03's now, i haven't found a 45RFE yet, i'm starting to think that April date is a bunch of whooey...

I love a challenge! Especially ones which I am prepared. Here she is in all her glory. And I know where it is to this day:

Beautiful, just not many options:

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Interior:

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Clearly a 45RFE:

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I took this picture back when I was selling it to boast that it indeed had the 45RFE.

You can tell by the angled crossmember. Now please believe me this is an 03. Unfortunately I never took a picture of the door jam showing the build date. I guess I could get a build sheet if you're still not convinced. If you have the 42 then you got a raw deal. Sorry.

 

[WesChapman]

Thanks

Thanks everyone. Seeing the difference between the two ratios doesn't justify the cost for me. Unless the economy and construction industry dramatically improves soon, my Renny won't see bigger tires and lift for a long time. And besides, I have a 78 IH Scout Terra with a lift and big tires. That's my off-road toy.
As far as the "Trash-loc", it will be fine for my needs. If the poster with issue against the Trac-loc would like to write me a check to pay for whatever they deem worthy, PM me for my address.

I still have to decide which child to sell to pay for this repair. Leaning towards the boy, he's more whiny than the girl. I think she is going to be the hell raiser. At 14 mos old, she all ready looks at the Scout and says "mine!"

 

[eyehatetofu]

If you search around here and on LOST you will see that the Trac-Loc doesn't last very long. I have no idea how much they cost but it seems like a waste of money. I don't have one, they were not available in '06 due to ESP / ABS / QWERTY electronic mumbo jumbo, but have seen numerous posts about longevity issues. There is a reason why they have been dubbed Trash-Loc. It you haven't searched around you might want to before investing anything.

 

[kjweston]

That's typical internet hype....don't throw a statement like that out, and not back it up with real world facts as to "WHY" you think it's trash...

Got documentation on Trac-Loc failures.....post it...
Got a friend that had Trac-Loc fail on him/her....get them on here to tell the story.....

Offer the OP other real world options, there's other limited slip differentials on the market that fit the Chrysler 8.25, and Dana 30 axles.....


Sorry Kjweston, but I'm loosing my patients with "Seagull" posts......

Seagull post.......when someone flies into an established thread, ***** all over it and flies away leaving no real redeeming information to help those seeking knowledge on any given subject.....

There's plenty of documentation mr. Surf guy. I take offense to your little opinion. Ask anyone that wheels their kj's and had a trash loc. It's not nicknamed that because someone thought it was catchy... But your seagull joke is clever I guess. Props for that..

 

[eyehatetofu]

He wrote "loosing my patients" instead of *patience*.

Paging Dr. SurfGuitar to the ER, Dr. SurfGuitar to the ER! We're losing patients due to an influx of seagull posts!

Sorry couldn't resist

 

[jcbll95]

If you want 4.10s try finging a 4 clyinder kj in the bone yard they should have 4.10s.

 

[Midgear]

That's typical internet hype....don't throw a statement like that out, and not back it up with real world facts as to "WHY" you think it's trash...

Got documentation on Trac-Loc failures.....post it...
Got a friend that had Trac-Loc fail on him/her....get them on here to tell the story.....

Offer the OP other real world options, there's other limited slip differentials on the market that fit the Chrysler 8.25, and Dana 30 axles.....


Sorry Kjweston, but I'm loosing my patients with "Seagull" posts......

Seagull post.......when someone flies into an established thread, ***** all over it and flies away leaving no real redeeming information to help those seeking knowledge on any given subject.....

QFT this post was awesome.

but anyhow.. carry on.

 

[KYLiberty]

That's typical internet hype....don't throw a statement like that out, and not back it up with real world facts as to "WHY" you think it's trash...

Got documentation on Trac-Loc failures.....post it...
Got a friend that had Trac-Loc fail on him/her....get them on here to tell the story.....

Offer the OP other real world options, there's other limited slip differentials on the market that fit the Chrysler 8.25, and Dana 30 axles.....


Sorry Kjweston, but I'm loosing my patients with "Seagull" posts......

Seagull post.......when someone flies into an established thread, ***** all over it and flies away leaving no real redeeming information to help those seeking knowledge on any given subject.....

OK, my trash lock broke and damaged my pinion bearing. Had the rear end rebuilt with a DTT. Much happier now.

 

[kjweston]

OK, my trash lock broke and damaged my pinion bearing. Had the rear end rebuilt with a DTT. Much happier now.

Holy sh*t! hey surfguy up there... Seems we have some hard evidence.