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4.56 or 4.88 gears?

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BlitzK5

1/2 ton status
Joined
Jul 29, 2005
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Location
Sherwood Park, Alberta, Canada
Need to now which gears to go with. I have 38" super swamper radials, 14 bolt in back in and a 10 bolt up front for now untill I get a Dana 60. Im running a 454 and a Th350. Im also looking at getting the black box and a NP205 from northwest fabrications so I will have a 5.33:1 low gear in the transfer case. Im thinking that I could go with 4.56 since I will get a good low range with the T-case and have lower rpms at highway speeds + since I got a 454 it would make up any lost torque from not going with 4:88's or lower. In the futrure I might go to 40's or 42's aswell but thats not untill I got a Dana 60 up front. What to you guys think would be the best for my setup? Im also not sure if 4.88 would be stong enough in a 10 bolt since the pinion would be so small. Is this a concern or would the axles and u-joints always go before the pinion?
 
BlitzK5 said:
Need to now which gears to go with. I have 38" super swamper radials, 14 bolt in back in and a 10 bolt up front for now untill I get a Dana 60. Im running a 454 and a Th350. Im also looking at getting the black box and a NP205 from northwest fabrications so I will have a 5.33:1 low gear in the transfer case. Im thinking that I could go with 4.56 since I will get a good low range with the T-case and have lower rpms at highway speeds + since I got a 454 it would make up any lost torque from not going with 4:88's or lower. In the futrure I might go to 40's or 42's aswell but thats not untill I got a Dana 60 up front. What to you guys think would be the best for my setup? Im also not sure if 4.88 would be stong enough in a 10 bolt since the pinion would be so small. Is this a concern or would the axles and u-joints always go before the pinion?
Click to expand...
X2!!!!!!!!!!!!!!!!!!!!!!
 
im going to be running a similar setup. im going to be running 4.56's with 42's and dual t-cases with an overdrive tranny. granted im running a diesel, at 65mph my rpms are going to be at 1850 which is the best for a diesel, while having a crawl ratio of 145, it should work out perfect.

if you are going to be driving the truck on the highway alot w/o overdrive, id go 4.56. if you plan to ever get an od tranny, id go with 5.13's. if its going to see limited highway driving and mostly trail/town id go 5.13's. uve got a bbc so youll have the power to turn them with 4.56's
 
I have 38's and 4.56's with a 700r4. I just have 350 tbi and in OD the truck just puts along at 70-75. If there is a lot of head wind I have to slow down to 65 or less otherwise the tranny will just shift in and out of 3rd. in 3rd gear at 70 i have plenty of grunt so im sure you will be fine with the 454.
 
I would stay tall on the gearing (i.e. 4.56) since you are going have all the slow-speed gearing you need going dual cases.
 
if you go with 4.56 gears you can find a 60 later that already has matching gears.

I would go with 5.13's or even 5.38's if you are considering regearing. you can never have too much gear,
 
Im running 4.10's with my 454/T350 and 38.5's. On the street its fine. Offroad I only really do mud so the 2:1 low on the 203 is adequate. But I have a 4.56 matching D60 and 14B that Im looking to swap in for a bit more grunt and acceleration.
 
Not to highjack to far but I got a d60 and 14 im regearing 454/700r4/208. Ive heard 5.13 are weak and twist pinions off. You guys think that will be a problem with a 14 and d60.
 
I would do whichever is cheaper cause the difference between 4.88s and 4.56s is not much. With a 454 I would probably go with the 4.56s because the motor has enough torque to deal with less than ideal gears.
 
BlitzK5 said:
Need to now which gears to go with. I have 38" super swamper radials, 14 bolt in back in and a 10 bolt up front for now untill I get a Dana 60. Im running a 454 and a Th350. Im also looking at getting the black box and a NP205 from northwest fabrications so I will have a 5.33:1 low gear in the transfer case. Im thinking that I could go with 4.56 since I will get a good low range with the T-case and have lower rpms at highway speeds + since I got a 454 it would make up any lost torque from not going with 4:88's or lower. In the futrure I might go to 40's or 42's aswell but thats not untill I got a Dana 60 up front. What to you guys think would be the best for my setup? Im also not sure if 4.88 would be stong enough in a 10 bolt since the pinion would be so small. Is this a concern or would the axles and u-joints always go before the pinion?
Click to expand...


Here's the analysis for you (your BEFORE and AFTER scenarios).....

Courtesy of CrawlCAD (coming soon for a download near you!) :D

CrawlCAD.jpg
 
WOW, now that's a program. When will it be available and were can I download it from? Thanks for putting in so much effort. But I don't see why your using 5.04 for the TH350. It has a first gear of 2.52
 
BlitzK5 said:
WOW, now that's a program. When will it be available and were can I download it from? Thanks for putting in so much effort. But I don't see why your using 5.04 for the TH350. It has a first gear of 2.52
Click to expand...

I just wrote that program yesterday.....sort of in response to all the questions I keep seeing about axle re-gearing and doublers/ aftermarket cases (Blackbox, STaK and Atlas).

The program has pulldown menus for each blue square, so far the options are:

Transmissions:

TH350
TH400
700R4
4L80E
NV4500 (5.61)
NV4500 (6.43)
T-56


Transfercases:

NP203
NP205
NP208
NP241
LoMax NP205
NWF BlackBox
STaK 5.44
ATLAS 5.44
ATLAS 10.34

Tire Diameters:

33" through 54"




The idea is to just select the driveline setup you currently have in the upper part, then build your "experimental" rig in the lower part. It should become obvious whether your parts selections make sense based on your objectives...

In your case, the deeper axle gears are not going to do all that much for your crawl ratio in the second scenario.....the "doubled-up" transfercases are where the REAL reduction is happening. The engine RPMs at highway speeds should be your guide also. I'm not sure if you're running 3.73s now or 4.10s, but anything much deeper than that and you're going to start punishing yourself on the highway.

My advice is to start your build plan with the tire diameter you know you want, and the highway RPM you want to run. Everything else can be worked backwards from that. If you don't have an OD tranny, you will use taller axle gears and a deeper set of gears in the transfercase. If you have an OD trans, you can run the deeper axle gears and less reduction in the transfercases...

BTW -> It's not a typo, the TH350 uses a 2.52:1 first gear.....I multiplied that by the stall effect of the torque converter (generally accepted as a 2:1 ratio) which results in the 5.04 number you see there. The program is smart enough to know which transmissions are automatics and which are manual, and only applies that extra correction factor for the automatics.

Glad you like the program! It will be posted up on www.gregblanchette.com probably early next week, since I'm taking off today for the Easter weekend.

:usaflag:
 
BlitzK5 said:
ok Thanks, I never herd about the stall effect thing before and that it give you a added 2:1 gear reduction. Can you explain further on this effect.
Click to expand...

The torque converter allows for slippage between the engine and tranny below it's rated "stall" RPM. When you start out at low RPM, the torque converter starts to move but there is not a 1:1 relationship between the engine RPM and with the input side of the tranny. As the RPMs build and the TC reaches it's stall speed, there is virtually no slippage....so the engine RPM is basically the same as the RPM on the input side of the trans. At that point, whatever "gear" you've got (in the case of the TH350 it's 2.52:1) is what you're ACTUALLY getting out the back of the transmission.

So in effect, below the stall speed the transmission is slipping at about 50% which is why you use the "stall effect" multiplier of 2:1.

Manual guys don't get that benefit, which is why you'll almost always see their trannies using a much deeper 1st Gear ratio than the slushboxes to compensate.
 
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