Best 8 Speed/Gears combo

I'm getting the itch to finally do the gear swap and throw in a Detroit TrueTrac at the same time. I'm lifted on 35's and currently have the 5 speed and 3.55 gears. If I was planning on sticking with the 545rfe or going to 37's I would definitely go 4.56's, but planning on doing the 8 speed swap at some point.

So would the 4.56's be too much or would 4.10's be better suited? Mostly city driving and not much towing. Did some searching on here and the FB pages but only looks a few guys have done this, especially the 4.10's. With me having an '11 the front swap won't be an issue either way.

Personally my truck has 3.92 with the 8 speed and feels great. If 4.10 wasn’t so close I would do 4.10 on my truck for that extra pep. I am tuned, headers, and 6.4 manifold so I know I’m pushing more power to begin with but had 35s before the tune and I could tell over the stock tires I had taken a hit but it wasn’t bad. After the tune I feel like I’m even better than I was stock. My next set of tires will be a 285/75r18 to drop weight and help bring back some mpg. If you are planning 37s I would definitely want 4.10s on the 8 speed. A few people have done 4.56 and swear by it but I feel like 4.56 would basically negate 1st gear unless you had tires larger than 37s. All personal opinion. Really depends on your plans for the truck too. I don’t feel like my truck struggles at all. My tire setup is 101lbs wheel and tire combo. I’ve got a tonneau cover, front bumper weighs 70lbs and my steps weigh 50lbs per side plus I’ve got around 50lbs extra in recover gear in the truck at all times and a full spare in the bed so it’s not a light truck. My average mpg is 13. Usually about 15mpg hwy

I appreciate the input man. As much as I'd love to go 37's for the looks I just can't justify it as the truck is big enough of a pig on fuel now and I'd like to keep as much performance as I can. I'm almost fbo now, 6.4 intake I may order with the gears actually. Did you find a noticeable difference with it? Then a cam down the road. I don't have any heavy bumpers or anything like that.

I'm sure I'll notice a drastic difference going to the 4.10's, just if I'm going to be dropping that kind of coin I don't want to be 2nd guessing myself after the fact. Especially being north of the border. My gut is telling me 4.10's but that little devil on my shoulder is saying don't fear the gear lol.

I wouldn’t go over 4.10 only because of how low 1st gear is in the 8 speed. It’s like a granny gear in the old trucks. The 6.4 manifold was actually a really big difference down low and I feel like it carries it through up higher better too. Granted the tune really did most of the work. I did have Hemifever set my shift points up to 6200 as well and man does it scream. I can spin the 35s easy. Sometimes do it accidentally if I’m not thinking about it. I have a cam in my plans too but just a small one.

4.56 with an 8 sp tranny is near a dump truck gearing.
Back in the day I drove a big old Ford F700 ton and a half dumper that had a split axle for loaded with dirt. What a granny gear!
You don't want that.

If you're really going to do the 8spd swap, 4.10 should be pretty good. But if there's a chance, even tiny, that you don't, 4.56 and don't ever look back.

Remember that the top ratio of both trans' is the same.

crazykid1994 said:

I wouldn’t go over 4.10 only because of how low 1st gear is in the 8 speed. It’s like a granny gear in the old trucks. The 6.4 manifold was actually a really big difference down low and I feel like it carries it through up higher better too. Granted the tune really did most of the work. I did have Hemifever set my shift points up to 6200 as well and man does it scream. I can spin the 35s easy. Sometimes do it accidentally if I’m not thinking about it. I have a cam in my plans too but just a small one.

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Yeah I hear ya, that's what I had heard about 1st gear on the 8 speeds. I guess if 4.56's were the way to go then a lot more guys would've done it.
Nice man! Did you get it ported? I'm wanting to keep the catch can too so I was actually looking at your thread the other day about what you rigged up, well done.
My cam won't be anything too crazy either, as this thing is still my daily.

HEMIMANN said:

4.56 with an 8 sp tranny is near a dump truck gearing.
Back in the day I drove a big old Ford F700 ton and a half dumper that had a split axle for loaded with dirt. What a granny gear!
You don't want that.

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LOL well when you put it like that...

caulk04 said:

If you're really going to do the 8spd swap, 4.10 should be pretty good. But if there's a chance, even tiny, that you don't, 4.56 and don't ever look back.

Remember that the top ratio of both trans' is the same.

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Yeah 100%! I plan on running this thing into the ground and I really can't see that happening with the 5 speed. Wish I hadn't sunk the money into the valve body/channel plate upgrades but if that keeps it alive for another year or so until I'm ready to start piecing together for the swap then I can't complain

4.10 with 35's is nearly identical to 3.92 with 33's which is still quite common in 8spd trucks.

Mine has the 3.21 which sounds awful, but the gears are spread so much and 1st is so short. Most of the time, I'm into 2nd gear by 10mph.

I went with the 4.88s with the 37s I have on mine .... I personally think that if you are going to regear and you have 35s then 4.56s is the way to go on the 8 speed ... anything over 35s you need the 4.88s to really justify a regearing and possibly 8 speed swap ...

Don't fear the gear seriously, my truck is damn fun to drive and I have no regrets, 2nd thoughts and no fear of the gears lol

I agree with above,

I have 3.92 gears and the 8 speed with the a tuned ecodiesel... plenty of power and get up and go but I lost just about 10mpg going from 31" tires and the truck being lowered by PO than stock to 34 inch tires and a 3/2" lift over stock... highway went from 32-34mpg to 22-23mpg and I get just under 16mpg with overall city driving vs 22-24 mpg before. The transmission also does much more down shifting and doesnt ever reach 7-8th gears unless on the highway with a light pedal. This might be different with a hemi but you would thing with a diesel making 500lbs of torque at lower rpms Id have it pretty good here. Dont get me wrong its much better than my 2nd gen 5.9 gasser with 35s and 4.56 gears. but I also have lighter 4ply tires on backorder and I may even step down to 285/70/18s if those dont work well.

augiedoggy said:

I agree with above,

I have 3.92 gears and the 8 speed with the a tuned ecodiesel... plenty of power and get up and go but I lost just about 10mpg going from 31" tires and the truck being lowered by PO than stock to 34 inch tires and a 3/2" lift over stock... highway went from 32-34mpg to 22-23mpg and I get just under 16mpg with overall city driving vs 22-24 mpg before. The transmission also does much more down shifting and doesnt ever reach 7-8th gears unless on the highway with a light pedal. This might be different with a hemi but you would thing with a diesel making 500lbs of torque at lower rpms Id have it pretty good here. Dont get me wrong its much better than my 2nd gen 5.9 gasser with 35s and 4.56 gears. but I also have lighter 4ply tires on backorder and I may even step down to 285/70/18s if those dont work well.

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My truck with the hemi hits 8th gear at 50 mph if I’m just cruising around. 35s and 3.92. My next set of tires is a 285/75r18 cooper discoverer at3 xlt. Only reason I’m changing is to hopefully get back some mpg. They’re only 59lbs each. My current 305/70r18 Mickey Thompson atz p3 is 71lbs each. Both 10ply rated

CAG CheechDogg said:

I went with the 4.88s with the 37s I have on mine .... I personally think that if you are going to regear and you have 35s then 4.56s is the way to go on the 8 speed ... anything over 35s you need the 4.88s to really justify a regearing and possibly 8 speed swap ...

Don't fear the gear seriously, my truck is damn fun to drive and I have no regrets, 2nd thoughts and no fear of the gears lol

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what’s your rpm while doing 75mph? I’m just under 2,000rpm and does your truck use first gear or shift straight to second when accelerating? I remember talking to you about this before when you were first planning on going 4.88. I kept thinking 4.88 was ridiculously low for the 8 speed because of how low 1st gear is. Also your crawl speed has to be stupid low and extremely strong. Bet you can pull a stump while idling in 4 low. Lol.

crazykid1994 said:

what’s your rpm while doing 75mph? I’m just under 2,000rpm and does your truck use first gear or shift straight to second when accelerating? I remember talking to you about this before when you were first planning on going 4.88. I kept thinking 4.88 was ridiculously low for the 8 speed because of how low 1st gear is. Also your crawl speed has to be stupid low and extremely strong. Bet you can pull a stump while idling in 4 low. Lol.

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At 75 my rpms are right below 2000, it does use 1st and 2nd but the progression is very quick ... in town it feels like a beast no joke ... remember I am only 2wd so no 4 low for this beast lol ...

crazykid1994 said:

My truck with the hemi hits 8th gear at 50 mph if I’m just cruising around. 35s and 3.92. My next set of tires is a 285/75r18 cooper discoverer at3 xlt. Only reason I’m changing is to hopefully get back some mpg. They’re only 59lbs each. My current 305/70r18 Mickey Thompson atz p3 is 71lbs each. Both 10ply rated

what’s your rpm while doing 75mph? I’m just under 2,000rpm and does your truck use first gear or shift straight to second when accelerating? I remember talking to you about this before when you were first planning on going 4.88. I kept thinking 4.88 was ridiculously low for the 8 speed because of how low 1st gear is. Also your crawl speed has to be stupid low and extremely strong. Bet you can pull a stump while idling in 4 low. Lol.

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Ok so my current tires are mickey thompson mtz (all terrain hybrid) tires (295/70/18 and weigh 69lbs each plus 12oz of balancing beads to keep them balanced in each wheel... the new nitto terra grapplers I just bought and waiting on are also the same size (34") but are only 4 ply and 51lbs each.(the tires that came on the truck used were 4 plt nitto terras in the 31.5" size at 43lbs each..) I learned from jeep years ago when going from a 31.5" kelly safari tire to a BFG 32.5" 10 ply tire how much the weight of the tire Crushes performance. I literally could not use 5th gear anymore from just that change until I swapped in 4.56 gears to replace the 4.10s after that my mpg and performance went way up and it felt like a 6cyl vs 4cyl. The MT were bought used and were meant to be temporary as the nittos have been on backorder since I placed the order in october.

I have a 1500 and do not tow huge loads so no reason for 10 ply tires... the reason the 1500s come with 4ply is for better ride quality and better mpg. I completely uderstand and respect they are not ideal for everyones use but I never carry more than 1200lbs (brewers grain) for short distances and only tow a popup trailer.