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gearing down...

T

tjhawk

NAXJA Forum User
Location
Appleton, WI
So I have these 4.56 gears on the shelf ready to be put into something but I am wondering a few things first. Right now I have 3.55 gears and 31 inch tires. On the highway at 60 I am turning 1800 rpm and I feel like I have to either drive in 3rd( I have an AW4 trans and a 4.0 litre) or keep my foot into it harder in 4th to keep the drag from my lift/tires/roof rack ect from slowing me down. It seems to pull harder above 2800 and so I was thinking if 4.56 gears would put me there then even better. Plus off road I would have a better time putting over stuff instead of having to goose it. BUT I also have an 100:1 kit for my transfercase and I could install that as well and have like a million to one low range or I could just install that and leave the gears as they are and deal with driving in 3rd when I am bucking a headwind or driving harder than normal. So my question to all of you is first what would my RPMs be with 4.56's on the highway? Also anyone got the 100:1 kit with deep axle gears and if you do how well do you like them?
 
I don't remember what the rpm's were, but go with the 4.56's. They go great with 31's. JIM.
 
Its just a tera 4:1 low kit but by the time everything is said and done your crawl ratio its like 100:1. Sorry for the misunderstanding.
 
One thing to keep in mind too is that you are putting a lot more torque into one location with just that tc kit. I had a suzuki samurai and this was a big topic of discussion among them since replacement tc gearsets are abundant for them. Putting new axle gears in puts the torque transfer down closer to where it's needed instead of putting it all in one spot that then has to put that power down driveshafts and out to your wheels.

Their argument, and I agree, is that you are putting a LOT of stress on the TC, mounts, and driveshafts and u-joints than should be delivered from that. While it's expensive, I'd say do the gears and still put in your tera low kit if you want to for offroad.
 
4.56's will definitely help in your city mileage. And may or may not decrease your hwy mileage.
 
i have 4.10 (4.11) gears and 31 inch tyres and 2250 rpm is 62 miles per hour (100kmph)

and 110 kmph is 2500 rpm, changing to 4.10 gears was the best money ever spent

plus i now get around 25 to the gallon with a mix of city and hwy driving

i personally think 4.56 is over kill on a street driven XJ with 31,s
 
Can you go lower?

I LOVE 5.13s and 35s for city driving and highway isnt bad, 3k RPM at 70mph. The RPMs keep me inside the legal speed limit :D As for offroad with lower gearing, its a non issue unless your doing some serious mudding or hitting the sand dunes. I wouldnt give up my 5.44 tcase low low for anything.

AARON
 
I think the 4.56's will be just fine. For one I have a set that was given to me years ago and never installed them so right there is a good reason to use them. I do alot of rock crawling and like going slow over things and not break things. Too many other people think that speed is the way to go and all that does is break axle shafts and rip out gears.
 
Ewenm said:
i have 4.10 (4.11) gears and 31 inch tyres and 2250 rpm is 62 miles per hour (100kmph)

and 110 kmph is 2500 rpm, changing to 4.10 gears was the best money ever spent

plus i now get around 25 to the gallon with a mix of city and hwy driving

i personally think 4.56 is over kill on a street driven XJ with 31,s
Click to expand...


What am I doing wrong, I just swapped in a 4.10s and rear detroit and get worse mileage on the highway. I might have to go 4.56.
 
If you have over 100K on them you need to change them out. Even though they are monitored by the OBD II ECU (1996 and up emissions specs) they can get lazy over time and not read quickly enough causing your fuel to not be metered quite as accurately as it should. I would only change the upstream one (at the minifold) as the downstream is just to monitor if your cat is working properly or not.
I changed mine out in my 1993 XJ and it cost me $60. I only gained 1-2 MPG on the highway and when gas was $4 a gallon that $60 got paid back very soon.
 
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