hey real quick I'm not happy with my 4.10's [img]images/icons/frown.gif[/img] Looking at new gears but I do not know if I should do 4.56 or 4.88's I've got a 258 (upgrading to mopar FI) and a T-5. I'm running 35" BFG muds, that are almost brand new. I thoug I was gonna get 33's but they were on backorder soI got 35's [img]images/icons/smile.gif[/img] [img]images/icons/smile.gif[/img] [img]images/icons/smile.gif[/img] What do you guys think on the gears, I would have done 4.56 but I do have the 5sp, With the od. Would 4.88's be to much for a DD that unfourtunatly see's more highway than off road?? Wehn I get new tires I'm thinking of going up to 37's, that's why I'm asking about the 4.88's
For anyone with 4.56 or 4.88 and 35's what kind of RPM's are ya'll turning? and how's the performance on the highway?? what kind of dismal gas milage?? I know it's good offroad TIA
Go with the 4.88s IMHO.
That's what I run with an OD NV4500 5 speed and 35s ... virtually the same setup as yours.
Put a 4.0 head in it when you do the MPI and you'll have a great combination.
Add a Tera 4:1 gear set to the D300 and you'll have an ideal 100:1 crawl ratio.
Your profile says '84 CJ. I assume a 20 in the rear and a 30 up front? Any thing lower than 4.10's for the 30 is really pushing it as far as strength. There is a lot less beef to the ring gear as it must be made thinner to accomodate the larger pinion. I would stick with the 4.10's and save for an axle swap. You will likely want it any how when jumping up beyond 35's. [img]images/icons/smile.gif[/img] My .02
For what it's worth, I run 33's (BFG MT)and 4.56's with a T5 and at 60 mph I'm running about 2400 rpm. I think that's a good highway rpm so as not to bog down the motor and still be able to make it up hills, headwinds, etc. I'd used 4.88's (strenght consideration aside) for 35 inch tires.
I`m in a similar boat... except I`m getting a new Ford 8.8 for the rear so that prompted the gear change... 35' Stock i6... I was debating 4.56 or 4.88 as well... from what I have heard the 4.88 is not the strongest in a d30 (still have that up front)..
So does everyone think a 4.88 would explode in the front dana30 when doing rock crawling?
I'll open this can of worms up for the 4.88 who has actually seen broken d30 4.88's? The early jeeps had 5.38's and 4.88's from the factory, did they blow them all the time? Order your gears from some where with a life time warenty and then if you break you get new replacemnts. If your breaking d30 ring and pinion you should probably upgrade your axle instead of dumping more money into it anyways. Also what kind of wheeling do you do? That plays a big factor in your gears.
Go with the 4.56 you will be more then happy with them and not have to worry about braking them as much. As far as the older jeeps with 4.88 and 5.36 the engine also only put out a minimal amount of horse power. (Can of worms resealed) I am going with 5.36 in a D44 front and rear but I am not sure how long they will last with 5.36. I also have put 4.56 in a new 5 speed TJ with true 33s on it and the RPMs are a in the 2700 range when going down the Interstate. If I had 4.88 and 35 or 36 I would still be in that same area. Its a little to high to get any engine life out of a Jeep. I will be replacing the 33s with 35s once I need a new set. this should put my RPMs back where they need to be.