how fast with 4.56?

SUA SPONTE · Apr 17, 2007

I havnt ever used 5th gear on my 87 renix man. tranny. No point as it is too low for effective fuel economy. I cant decide if i should run 4.56 or 4.88. Will be going with 33's but who knows. Thats what a lot of folks say before going to 35's. Is 5th gear going to be usable with 4.56 and 33's? How fast at what rpm's. Just another gear question- Thanks for the advice

DirtyMJ · Apr 17, 2007

I don't get how all you guys can't use your 5th gear stock.

Mine works great...

gixxer410 · Apr 17, 2007

If you go to 4wheelparts.com and go into the tire section there will be a tab for gear ratio chart. Click the tab abd use the guide. Otherwise I would go with 4.56 gears for 33'S.

Wounded XJ · Apr 17, 2007

I just had 4:56 put on my rig with 33's. I run about the 2500 rpm range at 65mph in 5th now, which is what I have been told you want. My mpg went up slighly. Before I could only use 5th on the down hills.

GrimmJeeper · Apr 17, 2007

4.56 with manual 4.88 with auto should be good up to 35s. you need less gear with a stick because you control when it shifts.

5-90 · Apr 17, 2007

DirtyMJ said:
I don't get how all you guys can't use your 5th gear stock.

Mine works great...

It can be used, but I (and a few others) have verified experimentally that fifth gear allows a crankshaft speed too low for optimal fuel efficiency. Running 30's and 31's on my stocker 88, I picked up 2-3mpg when I stopped using fifth gear, and cruising at freeway speeds in fourth. It still works - I just don't use it.

As far as crankshaft speeds at cruise, you just take the circumference of the tyre and figure how many revolutions per mile. Then, work backwards through the axle ratio and the OD ratio of the transmission... Make sense?

Ivan · Apr 17, 2007

DirtyMJ said:
I don't get how all you guys can't use your 5th gear stock.

Mine works great...

In stock condition, 5th gear works fine. But that goes out the window when you move up to bigger tires, and leave gearing stock.

Crap, at one time with 30's; 5th gear was like dragging a boat anchor for me. I've since moved up to 32's and 4.56 gearing, and the change is amazing.

I can't imagine what it would be like with 33's and stock gearing......ugh...

bigwillxj · Apr 19, 2007

Ive got 4.56's w/ 32's and a manual and I think it is a pretty badass setup. I will probably move up to a 33's when i get new tires b/c 32's do turn a fair amount of rpms(arround 2700 at 70 mph) on the highway(I know moving up wont help that much)

mattyg · Apr 19, 2007

going from 410s to 488s, 33s with a 2.5 is like stock gutless now not totally frickin gutless like before
but i'll never break my 8.8 LOL

how fast with 4.56?

SUA SPONTE

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gixxer410

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Wounded XJ

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5-90

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