4.56 for daily on a Magnum XL

[lenny127]

Basic story .... 14 track pack .... after a few years CJ FBO I went with a Vortech V3 (3.6) return fuel , 1050x injectors , twin pumps e85 full time always for years (3.31s out back) ... etc etc ... blew up my mt82 (rxt ) a month ago ... went with a Magnum XL (rxt) 2.66 ratio and went 4.10s out back .... I did my math before ordering the kit from JPC and while i knew everything would be a little longer I did not anticipate how it would actually feel .

Feels like the car now is pulling teeth before it gets going , car has plenty of power (695/565) but it feels like a pig and I am 100% sure last months car was faster than today's car.

I re did the math and this time I said screw it I want it to be as close to MT82/3.31 as possible .... and 4.56 and the 2.66 make the combined ratio of 1-4 almost identical in both mt82/3.31 and 2.66/4.56 scenarios .

the question is , is there any mechanical adverse effect of running 4.56 on a daily ... not an expert on rear ends , not sure if the temps go up and the diff needs more cooling with steeper gears .... that is my ONLY concern ... mileage the car has a 6th with .50 ratio so even with my 27.44 tall drag radial daily tires it would still do 65 mph at 1800 RPM with 4.56s ...so that is just fine .

Let me know your opinion please. thanks ( I do realize now I should have done 2.97 and 4.10 and it would have been better than 2.66 and 4.10 ... but 2.66 and 4.56 is still a better combo than both so if I can get away with it win win for me )

 

[me32]

Actually with the .50 6th gear the 456 would actually work good.

 

[lenny127]

yeah 6th/4.56 would cruise 1800 rpm ...... my 1st and 2nd would be within less than 1 mph of the mt82/3.31 combo so thats perfect ....and 3rd/4th with 4.56 ends up being 6 mph shorter by redline (7500) in both gears vs mt82/3.31 and again that is perfect because to me on the mt82 3-4 felt a hair long ... so tightening up those two gears should make the car even peppier ... engine loves 5500-7500 so the more i keep it there the longer it will last experts tell me lol .... 4th with 4.56 comes in at 135 mph at my limiter of 7500rpm so even for the track is perfect since my car should cover 130-134 traps ..... spoke with a tuner friend a little while ago and he tells me one of his customers is running a magnum with 5.13s out back as a daily and it fine no issues. 4.56s it is

 

[me32]

yeah 6th/4.56 would cruise 1800 rpm ...... my 1st and 2nd would be within less than 1 mph of the mt82/3.31 combo so thats perfect ....and 3rd/4th with 4.56 ends up being 6 mph shorter by redline (7500) in both gears vs mt82/3.31 and again that is perfect because to me on the mt82 3-4 felt a hair long ... so tightening up those two gears should make the car even peppier ... engine loves 5500-7500 so the more i keep it there the longer it will last experts tell me lol .... 4th with 4.56 comes in at 135 mph at my limiter of 7500rpm so even for the track is perfect since my car should cover 130-134 traps ..... spoke with a tuner friend a little while ago and he tells me one of his customers is running a magnum with 5.13s out back as a daily and it fine no issues. 4.56s it is

Seems like you got your answer. Should make for a great all around setup

 

[lenny127]

Yeah ratio wise I’m set , just was looking for any negative mechanical feedback on running 4.56

 

[me32]

Yeah ratio wise I’m set , just was looking for any negative mechanical feedback on running 4.56

As long as there installed right there should be no negative mechanical issue. Just make sure you get your tune set for the new gears.

 

[lenny127]

As long as there installed right there should be no negative mechanical issue. Just make sure you get your tune set for the new gears.

my concern was that of heat possibly and seeing if a cooler was advisable or I am worrying for no reason .... if I don't know something for sure I rather ask around and get a general consensus .

getting it done the week after next , I feel good about the decision ..... I am honestly shocked at how badly I missed the mark on the gearing ...I thought the 4.10s being slicghly longer now would ease traction ...but all it did was turn it into a slug lmao ... thanks for the input

 

[olaosunt]

Lol
When I did my Magum swap XL (2.66 first gear ) swap in my KB car I kept the 3.31's I had with my MT82 .

Now that was a slug on the street ...but it allowed me to stay in third gear up to 148 mph with a 27 inch tire.
I thought one less shift would increase my chances of going 9's but it was too much of a dog out of the hole .
After several 10.0-10..1's@145-148 (with high 1.5x 60's and best of 6.5@108 in the 1/8) I gave up .
I swapped in a pumpkin with 4.10 gear and off course it now feels like a rocket to me . Lol
I am having to learn how to launch the car again .
With the 3.31's in the rear I could side step the clutch with the 2 step set at 4000-4500 and it would dead hook with a 27 inch slick .
Not it's just spin city

 

[olaosunt]

Obviously the 4.56's won't work with the KB car since I trap high 140's(looking for low 150's ).
I have toyed around with swapping in a 4.56 pumpkin in my GT 350 to see how it feels .....I was going to strap on a whipple(sitting in boxes since feb) but now getting cold feet .

 

[lenny127]

yeah currently my car can hit 150 at the 7500 limiter we set ...... even the 4.30s are longer than mt82/3.31 .... when i finally did the math on the 4.56 then it was obvious why things were so off . The 4.56 with the 2.66/1.78 is almost identical as the 3.66/2.43 first and second on the mt82 with a 3.31 .... so I am literally not changing anything by going 4.56 ...now 3 and 4 do lose about 6 mph by 7500 so that cuts 4th to 135mph @ 7500rpm ... my car makes 695/565 and it full weight so it would never see beyond 135 mph at the strip . Now 3rd and 4th are going to feel a little peppier so I am looking forward to it .

 

[me32]

my concern was that of heat possibly and seeing if a cooler was advisable or I am worrying for no reason .... if I don't know something for sure I rather ask around and get a general consensus .

getting it done the week after next , I feel good about the decision ..... I am honestly shocked at how badly I missed the mark on the gearing ...I thought the 4.10s being slicghly longer now would ease traction ...but all it did was turn it into a slug lmao ... thanks for the input

Are you road racing your car? If not a cooler is not needed. Running a great rear diff fluid is what matters and if you have ford LSD add ford motorcraft friction modifier. The 456 is not gonna add a bunch of heat DD the car. Drag racing is not an issue either. Since you make a pass get a cool down and run it again. Road racing would be the only reason you may need to add a diff cooler. That would be with pretty much any gears.

 

[biminiLX]

4.30 and run more boost.
-J

 

[lenny127]

Are you road racing your car? If not a cooler is not needed. Running a great rear diff fluid is what matters and if you have ford LSD add ford motorcraft friction modifier. The 456 is not gonna add a bunch of heat DD the car. Drag racing is not an issue either. Since you make a pass get a cool down and run it again. Road racing would be the only reason you may need to add a diff cooler. That would be with pretty much any gears.

car won't pass tech now so drag racing is out for a while , this car is a keeper for me and will always be my daily . I am not concerned with drag races , more like prolonged freeway speeds of say 75-80 for an hour say or two hours .... that is the only scenario that concerns me ... in 10 seconds the gear oild ain't gonna cook so drag racing isnt an issue. I run a torsen (track pack) so no modifier.

4.30 and run more boost.
-J

stock long block 2014 ... car is at 700/565 on 10 psi .... if anything I may throw on an 18 manifold but boost is something that will most likely shorten the life of the engine drastically. The 4.56 will be good.

 

[biminiLX]

Yep don’t fear the gear, especially when you have a high rpm engine and 0.50 top gear.
I love the 4.10 in my GT500 with Magnum XL
-J

 

[lenny127]

oh yeah ... i run a 305/35/19 NTO5R as my daily tire , its 27.44 tall ... with the 4.56 and my ratios I can still do 65 mph @ 1800 RPM in 6th ...so the 4.56 sounds like a lot but I can still hit 135 mph with 4th 1:1 ... and I have the cruise mpg .... couldnt have been more perfect if I had done this by design . I do wish I could keep first how it is now with the 4.10s ...way more usable .... but overall it't the right move.