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Parts to change TJ Ratios

1K views 16 replies 6 participants last post by  Irish4x4 
#1 ·
Hi Guys,

1st post here. Need some advice on changing diff ratios.
I have bought a 'new to me' 98 TJ with 34" Tyres.

Looks great, drives like stink. Have it 2 months and havent used 5th gear yet.

Anyhow I have decided to correct the ratios to 4.56.

Parts are in short supply here in Ireland so will probably purchase from USA, likely Quadratec who I have already used to replace the tired soft top.

Buying the Crown and Pinion is a doddle. Issue is, do I need anything else.
Its a low miles Jeep so I could do without changing bearings, carriers etc if not required. But at the same time I could do without having to place a 2nd order for parts as I will have to pay International shipping plus it takes about a week for parts to arrive.

Any advice on parts required would be helpful.

Dana 44 and 30 axles

Cheers
 
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#2 ·
I would get install kits with the gears. They come with new bearings, shims, crush sleeve, etc to install your gears. You will likely need to reshim, and having the parta there to do so will be handy.
 
#3 ·
The plot thickens. Last night I decided to check what ratio is currently in my rear axle. Can't read the tag so was going to spin a wheel (2 rotations to allow for the other side not turning) and count the pinion revoloutions. However when I jacked it up on 1 side the tire wouldnt move. Jacked up both sides and both tires spun the same direction? Does this suggest that a previous owner has fitted a LSD? Might have to crack it open and see whats in there.

Anyhow after 1 revoloution of both wheels the drive spun just short of 4 times so it looks like whatevers in there it is at 3.73 ratio which is why my TJ on 34's is so slow.

I still reckon I would be better off with an open 4.56 rather than a posi 3.73.
 
#4 ·
If you have the 4.0l and 5 speed, i suggest you go to 4.88's for that size tire, but understand that there is a whole lot more to setting up gears than just bolting in parts. It takes precise measurements with tools that the average home mechanic doesn't typically have.

I suggest you have a shop do it, and let them supply the parts.
 
#5 ·
Certainly sounds like you have a LSD. If you haven't already - check your build sheet - https://jeep.custhelp.com/app/jeep/eqlisting_detail/ -

Just enter your VIN and it will tell you what it came with. Maybe you've got a D44 rear with a posi-trac LSD and 3.73. If that's the case you will need thick cut gears or a new carrier for the 4.56 ratio. At any rate, I would still open it up to see what you've got as it will effect what you gears you need to order.
 
#8 ·
Right guys. Eventually got a good day to open up the diff cover. When I removed the bolts I was able to dig out 2 tags from the several layers of Waxoyl. I cleaned these up and have attached pictures. They also suggest a LSD as the ratio tag has 3.73 on it and LS is also mentioned? The other tag says
USE LIMITED SLIP DIFF LUBE ONLY
. So thats all pretty clear, however with the cover off it just looks like an open diff to me. I would have expected a LSD to have the gears enclosed in an inner casing as this seems to be how an after market LSD is sold.





 
#9 · (Edited by Moderator)
Nah, it's probably got a trac-lok. They look very VERY similar. the only difference is in the clutch plates that are located underneath the side gears. check out this video from yukon on how to rebuild - it shows where the plates are located.

http://www.youtube.com/watch?v=fbjPT1JdQKw
 
#12 ·
please do not take offense to this, but the questions you are asking are making it clear that you are not familiar with setting gears.

its a rather difficult task, even for very experienced mechanics. if you are off by a tiny bit, it will destroy the gears and then back to square one with a few hundred less in your pocket

its not impossible to set your own gears, but it does require a few specific tools and a lot of patience. here is a very in depth guide. Pirate4x4.Com - The largest off roading and 4x4 website in the world.
 
#13 ·
To clarify, I am in Ireland and Jeep aftermarket parts are in short supply here so I am trying to establish what I need to order as I will be getting them shipped from USA. The fitting will be done by a mate of mine that is an experienced Ford mechanic who has access to all the tools required.

While advice is much appreciate I would prefer if we could stick to the original topic.

Cheers
 
#14 ·
Gears and install kits will cover everything you need. The install kits include new bearings, shims, bolts, seals, crush sleeve, marking compound, etc. Some kits don't come with bearings, but you'll probably need new ones and maybe setup bearings (unless your friend has the tool to remove the bearings without damaging them - like this one - https://www.quadratec.com/products/52465_9900_07.htm )
 
#17 ·
Thanks very much guys, Gear & Install kits it is then for Dana 44 & 30.
Looking at this set https://www.quadratec.com/products/52466_001X_PG.htm
Seems better value than buying front and back seperately.

Just double checking, I can go from 3.73 to 4.56 on the same carriers?

RD3 I am in Co Fermanagh which is in the North. Clifdens a nice part of the country. Heading to Westport myself for Easter.
 
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