Lift, and tire question

[XXLMJ]

I have a 88 MJ I'm putting in a 5speed, 4.0, 4x4. The gears in the rear now are 3.55 What is a good tire size for this gearing. I was wanting to do a SOA lift. And run 33s, but if thats gona be too much tire for my gears i can change. I'm just now starting this project so there is alot of room for change yet.

[CWLONGSHOT]

It will be drivable for sure, 4:10 would be better but its not nearly as bad as if you had 3;07's!! You may loose 5th in the hills, but that's about the worst of it.

 

CW

[XXLMJ]

A spring over seems like the best way to go. Am I right of should i do a normal lift with new spring packs. I do plan on driving this on the road, will a SOA hurt my street driving.

[mnkyboy]

Mine is a daily driver. I have a 5" lift and SOA,it drives fine on and off road.

 

I also have 3.55 gears with 33X12.50's but i have a 2.5L/AX4,Its not a rocket ship but its not completely gutless either so you should be fine with 3.55s and a 4.0L

[MiNi Beast]

SOA is a grat option and cheap as well, but need a welder or someone of know how. Lift packs and keeping it under will make the install more hands on and more or less bolt on and will ride good on the road as will the SOA set up will as well. What are you looking to do as far as with your truck, haul with it regularly, look good and get you back and forth to the beach and work, trail ride on the weekend, just trail rig, is this your daily driver? As you can see many option and best place to start is to figure what you want to do with it before you put money into it then later change it and put more money into something you could of already had and basically just bought twice, you see the thinking in that?

[mvusse]

The stock ratio for a 4.0/5 speed is 3.07. 3.55 gears will give you very close to the same final drive ratio running a 32 or 33" tire.

[Eagle]

My view is:

 

3.54 for stock tires

3.73 for 30" tires

4.10 for 31" tires

4.56 for 32" tires

4.88 for anything larger than 32" tires (4.88 is the deepest gear available for the Dana 30)

[XXLMJ]

WOW thanks for all the info! The truck will be driven daily to work, on the weekends i plan on doing some mild wheelin, and a hunting truck during the winter months. As far a hauling, a quad would be the most i would haul in it. I was wanting to run the 33s cause it just looks cool.

The truck was a 4.0 2wd auto and I'm changing all that, thats how I'm getting the 3.55 gears.

SO i guess my next question how much of a lift does a SOA give you? Will 33s look ok? Or is that too much of a lift?

[mvusse]

SOA will usually give you ~6" of lift. Coupled with 6.5" in the front it looks good, and is about the right height for 33s.

 

You can run 33x10.50 with 4.5" in the front, but 33x12.50 can be problematic with anything less than 6.5".

 

And Eagle, is that table you posted your general solution for any engine/transmission, or specifically a 4.0 stick shift?

[akamcbird]

My view is:

 

3.54 for stock tires

3.73 for 30" tires

4.10 for 31" tires

4.56 for 32" tires

4.88 for anything larger than 32" tires (4.88 is the deepest gear available for the Dana 30)

 

could you explain this better? ive read multiple posts that all have similar numbers but these seem a bit tite from one size tire to the next.

 

over the years ive come to trust your opinion on anything that involves math and technical fact, but wen i look at the math posted elceware and the random calculators, these numbers just look off.

 

i assume that these numbers are were they should be and not what they would be to keep the factory final drive ratio :dunno:

 

did i answer my own question?

 

for example: had 28"tires with a 3.07 ratio and wanted to go to 33" tires i would want a 3.62 ratio. but why would i want the same 3.07 bs so up it to 3.73.

http://www.izook.com/gearcalc.htm

(i went 4.10 from 3.07 wen i got 33" tires)

[Darren]

My view is:

 

3.54 for stock tires

3.73 for 30" tires

4.10 for 31" tires

4.56 for 32" tires

4.88 for anything larger than 32" tires (4.88 is the deepest gear available for the Dana 30)

 

I hope those ratios are your recommendations for the automatic, he said he is putting in a 5 speed. I had 4.56's and 31's with a ba-10 for 3 days. I couldn't do freeway speeds, (topped out at ~60mph) and the ba-10 could only handle the torque for 3 days before it literally blew up.

 

Note: I blew up the BA-10 driving like a jackass. I couldn't control myself, the power that 4.56's a Detroit and 31's had, I just couldn't help myself. It's final moment was a 3rd gear clutch drop at 4000 rpm. The noise that followed sounded like a blender full of scrap metal. But I had an AX-15 I was swapping in so I didn't care.

[Pete M]

SOA is only cheap in the rear. Balancing that out with 6" up front is expensive. Is there something wrong with a good 3" lift and 31" tires?

You know for sure the gears are 3.55, yes?

[Eagle]

My view is:

 

3.54 for stock tires

3.73 for 30" tires

4.10 for 31" tires

4.56 for 32" tires

4.88 for anything larger than 32" tires (4.88 is the deepest gear available for the Dana 30)

 

could you explain this better? ive read multiple posts that all have similar numbers but these seem a bit tite from one size tire to the next.

 

over the years ive come to trust your opinion on anything that involves math and technical fact, but wen i look at the math posted elceware and the random calculators, these numbers just look off.

 

i assume that these numbers are were they should be and not what they would be to keep the factory final drive ratio :dunno:

 

did i answer my own question?

 

for example: had 28"tires with a 3.07 ratio and wanted to go to 33" tires i would want a 3.62 ratio. but why would i want the same 3.07 bs so up it to 3.73.

http://www.izook.com/gearcalc.htm

(i went 4.10 from 3.07 wen i got 33" tires)

The only way to actually calculate equivalencies is to use the revolutions per mile for the different tire sizes. NONE of the on-line calculators do that -- they use the nominal diameter, so they are incorrect from the start. The spreadsheet I made up many years ago was created after researching a lot of tire brochures and manufacturers' web sites to obtain revolutions per mile. (And, of course, another tire of the same nominal size would be slightly different.)

 

To answer your question, the ratios I recommend have NOTHING to do with matching the factory ratio. The 3.07 ratio, especially, was a factory mistake from the outset. They used that for one reason: to optimize the mileage and emission ratings on the old government tests. For actual driving, the 3.07 ratio is a joke. 1600 RPM at 60 MPH in 5th gear? Even the non-HO version of the 4.0L engine has its torque peak at 2400 RPM ... the gear ratio should be chosen to cruise on the torque peak at highway speed. Even 70 MPH was only 1883 RPM with the 3.07s. 3.73s get you up to 2287 RPM at 70 MPH (on stock tires) ... that's getting closer to where it should be.

 

The ratios I suggested above are for a balance between daily driving and having a decent crawl ratio for off-road. No attempt was made to match factory final drive ratio.

[akamcbird]

The only way to actually calculate equivalencies is to use the revolutions per mile for the different tire sizes. NONE of the on-line calculators do that -- they use the nominal diameter, so they are incorrect from the start. The spreadsheet I made up many years ago was created after researching a lot of tire brochures and manufacturers' web sites to obtain revolutions per mile. (And, of course, another tire of the same nominal size would be slightly different.)

 

To answer your question, the ratios I recommend have NOTHING to do with matching the factory ratio. The 3.07 ratio, especially, was a factory mistake from the outset. They used that for one reason: to optimize the mileage and emission ratings on the old government tests. For actual driving, the 3.07 ratio is a joke. 1600 RPM at 60 MPH in 5th gear? Even the non-HO version of the 4.0L engine has its torque peak at 2400 RPM ... the gear ratio should be chosen to cruise on the torque peak at highway speed. Even 70 MPH was only 1883 RPM with the 3.07s. 3.73s get you up to 2287 RPM at 70 MPH (on stock tires) ... that's getting closer to where it should be.

 

The ratios I suggested above are for a balance between daily driving and having a decent crawl ratio for off-road. No attempt was made to match factory final drive ratio.

 

 

thats why...

over the years ive come to trust your opinion on anything that involves math and technical fact

[Eagle]

I hope those ratios are your recommendations for the automatic, he said he is putting in a 5 speed. I had 4.56's and 31's with a ba-10 for 3 days. I couldn't do freeway speeds, (topped out at ~60mph) and the ba-10 could only handle the torque for 3 days before it literally blew up.

You must have had a very sick puppy of an engine, because 31" tires with 4.56 gears would equate to 2233 RPM in 5th gear at 60 MPH.

[XXLMJ]

SOA is only cheap in the rear. Balancing that out with 6" up front is expensive. Is there something wrong with a good 3" lift and 31" tires?

You know for sure the gears are 3.55, yes?

 

No there is nothing wrong with a 3" lift and 31" tires. Thats just what i have now and was wanting to build the new one a little taller. I was just wanting some input on a SOA lift and how it handles. I still have some time to think about it.

[Pete M]

spring wrap can be a big issue with SOA.

[MiNi Beast]

spring wrap can be a big issue with SOA.

 

 

feeling tired tonight? Don't just leave it like that you'll scare him away from a soa, for what I think he wants to do he would be fine with it for what he is wanting to do. And you should get right around 5-5.5'' of lift with it. But really I think for an overall great ride with a little more lift I go with new leaf pack 4.5" lift set up and run 32's. I think you would be happier in the end.

[mvusse]

I run RuffStuff spring perches (they're 7 or 8" long), and have no more axle wrap than I had spring under.

[CWLONGSHOT]

Axle wrap is always an issue with a spring over. Its simple physics. With the spring on top of the axle tube, it has more leverage to twist the spring than it did as a spring under. How mush of a problem will only be determined by the springs condition, traction available and the weight of your right foot. :brows: :yes:

 

As Mvusse just mentioned one good method of resisting spring wrap is to use a long spring perch. Another way is to retain that heavy overload leaf from the factory pack.

 

Now the springs condition is unknown as our trucks are 20 + - years old. New springs may be the only option for some very tired packs.

 

SOA setups are just fine if you use your head and follow these simple steps.

 

CW

[XXLMJ]

I was thinking the SOA because i thought i could save a little cash by doing this. But i never realized that it would give so much lift, and the cost to get the front up to par may be to much. But i do want to thank you all again you all have very good info and i will be a great in helping me make my decision.

[socal1200r]

Heard the same thing...SOA is the inexpensive way to get big lift in the back, but the offsetting lift for the front is $$.

 

Another question along these lines...what's the largest tire one can run on stock 15x7 Jeep alloys, without a lift? I have 225/75-15 Michelins on there now. Could I run 30's, or possibly 31's, without any rubbing or bottoming out issues? My Comanche is 4wd, 2.5 4-cyl, 5-speed, 4.10 gears. I have a set of 30's on a '98 GMC Sonoma 2wd, and they rub the frame when turned full lock.

[Eagle]

Another question along these lines...what's the largest tire one can run on stock 15x7 Jeep alloys, without a lift?

31x10.50-15 ... on stock Jeep rims. 31s will still tuck up inside the sheet metal. There will be slight rubbing on the lower control arms when the steering wheel is cranked all the way to lock, but that's something that you quickly learn to avoid ... or you can shim the steering stops to block it. Install WJ LCAs, and they have an offset bend that cures this completely.

[mnkyboy]

my old 31X10.50's rubbed worse on stock wheels with no lift then they did on aftermarket wheels with a wider offset.

 

When i bought my truck one aftermarket wheel up front was missing and had been replaced with a stock one,the rubbing on the control arm was far worse then anything i experienced on the side with the aftermarket wheel,i replaced the stock wheel and it quit rubbing

 

I think the lighter 2.5L makes the front sit a little higher then a 4.0L truck so the tires clear better, I didnt have any rubbing till i added a heavy winch bumper and even then it was very little.

 

now my 4.0L XJ was pretty much undriveable with 31X10.50s/wide offset wheels and no lift.

[Eagle]

my old 31X10.50's rubbed worse on stock wheels with no lift then they did on aftermarket wheels with a wider offset.

 

When i bought my truck one aftermarket wheel up front was missing and had been replaced with a stock one,the rubbing on the control arm was far worse then anything i experienced on the side with the aftermarket wheel,i replaced the stock wheel and it quit rubbing

The wider offset (less backspacing) of aftermarket rims eliminates the rubbing on the lower control arms, but then 31x10.50 tires won't stuff inside the flares so you either have to trim or greatly extend the bump stops (which eliminates almost all suspension travel). The tires are also very likely to hit the lower trailing corner of the wheel well openings on sharp turns with less backspacing than factory rims.

 

IMHO stock rims are the way to go, and if you can't tolerate the LCA rubbing then replace them with the WJ LCAs.