Topic: 31 MTs with stock gearing

[chrisfranklin]

I figure with this setup --31MTs and stock gearing -- you lose 5th gear on inclines and sacrifice some mpg.  But is on-road drivability that much worse than with 29 ATs?  Maybe a bit of a loss in acceleration, maybe some more road noise, lower top speed.

I'm running out of rubber on my current ATs (Bridgestone Revos btw -- great tires for more than 4 years), so I am considering 31MTs, maybe BFG or Firestone's Destination.

[oldjeep]

You're not going to lose 5th gear with tires that small.  I'm running 35's with stock gearing.

[stan98tj]

road noise aint gonna be that bad either

[TahoeYJ]

I'm running 4:88 gears, and with my jump from 33's to 35's, it was hardly noticeable. I think you'll be just fine 

[DodgeMudder]

I ran 31s w/ stock gearing for years and didn't have any problems.  Heck I ran a while w/ 34's and stock gearing and other than making 5th a little useless, it was livable.

[jfrabat]

I ran 31's (HT, not MT, so a bit smaller than MT) for about 2 years with the stock gearing (4.10).  Now I have 4.88 with the same tires, but I am planning to go up to 33's MT in the near future (I regeared for 33's).

Regarding 31's with stock gearing, you will have to downshift to 4th at highway speeds if there is a headwind or if you are going up an incline.  Other than that, it drives fine, so feel free to go ahead and do it...

Felipe

[CliffB]

I have 31x10.50 BFG A/T with stock 4.10 gearing. No problem.

[aka-justin]

I have some procomp 31 mt's.  Only had to change my rims, because they were so wide when I turned the wheel, they rubbed on the leaf springs.  They also are a bit noiser, a tad less power, but I don't need gears.  I did upgrade my throttle body for better hill climbing and mud.  Well worth the $20.

Justin

[Bill M.]

I have some procomp 31 mt's.  Only had to change my rims, because they were so wide when I turned the wheel, they rubbed on the leaf springs.  They also are a bit noiser, a tad less power, but I don't need gears.  I did upgrade my throttle body for better hill climbing and mud.  Well worth the $20.

Justin

 
There is a TB that helps you crawl though mud??

Where can I get one? 

 

[Torch_Ind]

I wouldn't go any bigger then 31's for off road use with the 2.5L & 4.10/4.11's. very hard on the clutch drive line and engine making it work and redlining to get to a decent rpm range in the next gear. when i ran 31x10.5R15's with my 4.11's it was a great combo. when i went to 33's I burnt out my brand new clutch in less then a year from take off and crawling in the bush. I have currently just re-geared my diff's to 4.88's for the 33's witch is the most you can get out of the dana 30 up front. and seams to be a great match but I don't want to go any bigger tire or I would want to re-gear again witch would required changing the diff's. plus the dana 30 on the axle chart only recommends up to 32's-33's and the dana 35 only recommends 33's.

but going to 31's is fine really it's only 1/2-1" difference in lift 1-1 1/2 total tire size.

[st.chevrolet]

plus the dana 30 on the axle chart only recommends up to 32's-33's and the dana 35 only recommends 33's.

For anyone who thinks that a stock Dana 30 is a weak axle, I invite you to check out the link below for a video on you tube of my buddy's truck. It is a 90 S-10 Blazer with a 95 Chevy 350 TBI, rear axle is a 8.8 from a 91 Explorer, and the front is a stock Dana 30 from a Jeep Cherokee. The tires are 33x12.5R15 BFG Muds, now the way my budz drives with a heavy foot, I dont think there is any way you can say that little axle is weak. Now it is an open diff but still the abuse that i have seen the Dana 30 axle take from a V8 and 33's would say that for what the Dana 30 is it is not to bad in the strength Dept.

   http://www.youtube.com/watch?v=OarnTF2jCME

[JeffsJeep]

Why does it say when I try to send someone a PM by clicking on their name that "many apologies, but you cant view just and profile"
What the hell is that about? Since when?
Anyway, I was wondering how you got a bigger (I'm assuming you got the 4.0 TB) throttle body for 20 bucks 1995yj? Sorry if this is off topic, I tried to PM you but the above happened.

[jfrabat]

Why does it say when I try to send someone a PM by clicking on their name that "many apologies, but you cant view just and profile"
What the hell is that about? Since when?
Anyway, I was wondering how you got a bigger (I'm assuming you got the 4.0 TB) throttle body for 20 bucks 1995yj? Sorry if this is off topic, I tried to PM you but the above happened.

I would guess, junkyard...

[Torch_Ind]

i got one off a buddy who was parting out a jeep for 20$

[Torch_Ind]

For anyone who thinks that a stock Dana 30 is a weak axle, I invite you to check out the link below for a video on you tube of my buddy's truck. It is a 90 S-10 Blazer with a 95 Chevy 350 TBI, rear axle is a 8.8 from a 91 Explorer, and the front is a stock Dana 30 from a Jeep Cherokee. The tires are 33x12.5R15 BFG Muds, now the way my budz drives with a heavy foot, I dont think there is any way you can say that little axle is weak. Now it is an open diff but still the abuse that i have seen the Dana 30 axle take from a V8 and 33's would say that for what the Dana 30 is it is not to bad in the strength Dept.

   http://www.youtube.com/watch?v=OarnTF2jCME

I'm not saying that it won't take some abuse. but it could also be luck. plus if it's not rated that heavy your risking breakdown. and if your like me and run miles back in the bush for a run you don't want to blow a axle. or even risk it. I have lots of buddy here with stock axles running 35's to 38's. and I have seen them shear mounting brackets completely off and do gear and axle damage shear spines or even split cases . if your willing to pay the tow bill vs just building it stronger or not exceeding the max suggesting your running the risk of failure components.