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Discussion Starter #1
Alright, I have read through quite a bit on the recommendations for gear sizes, and my calculations show 5.38 gears to be my best choice, which seems like a very low gear ratio, specially compared to what most others are running. This would be for only 35 inch tires, so I want to verify if I am doing my calculations correctly or see what most of you guys are running.

It has a 302 with AOD tranny. BTW I still have the 29 inchers on the truck. Engine runs just fine, bone stock, and well maintained. My experience with the engine is the low end of the torque range starts to kick in at a little over 2000 rpms, which is really apparent on the freeway. At 65, when I drop it into OD, even though the truck pulls fine, I actually have to push the gas pedal down to maintain speed, resulting is worse MPG. I actually run 3rd gear until about 70-75, especially if I am on an incline or driving against the wind. (I use OD at much lower speeds when wind resistance isn't killing the truck). Once the rpm's get up higher, OD works great. It reacts the same from a stop light, kindof doggish until the truck hits 2000+ rpm's, then it starts to really take off. I found one single torque curve of a stock 302 online, which agrees with this showing the engine doesn't really make much torque until about 2000+ rpm's, but I have no idea about the accuracy of that torque curve. *now supposedly my engine was replaced about 20000 miles before i got the truck and maby its a mustang motor? with a lousy cam profile for a truck? Or mine isn't running correctly? I don't know but its how mine seems to perform* :banghead

So based on this it seems turning 2100 rpm's would be the best for cruising at 65 mph for mpg ect. Supposedly the truck makes max torque at 2400 from what I could find on the internet. Based on calculations, the truck is only turning 1800 rpm's at 65 in OD with the 29 inchers. I verified it by taking the truck out. Sure enough. Well this means I would need 4.11 gears just to get 2000+ rpm's for the stock tires. :shocked Putting on 35's would require 4.88 to get to 2040 rpm's in OD at 65. 2100 + seems optimum from my experience driving the truck (results in the least skinny pedal action), so I come up with 5.13 gears giving me 2150 rpm's. Now add in the fact that I may want 36 inch tires, as I do have a 6 inch lift on the way, or even maby travel at 60 without downshifting, and I'm looking at 5.38's. Not to mention the truck is now turning more mass and has increased rolling resistance (although this may not be a big factor), and probably needs additional torque.

What's the deal here? Is my engine just not running correctly and I am missing a ton of low end torque below 2000 rpm's compared to the normal 302, say around 17-1800 rpm's? Even with 5.38's I'd still only be turning 3300 rpms at 95 MPH, I did get a ticket once of 96 mph in the bronc :doh0715:

Hopefully you guys can point me in the right direction before I drop way to low of gears in my truck. Maby my calculations are incorrect?

Heres the equation I am using, based on 1:1 Transfer case and .67:1 AOD in OD. RPM=Transfer case X Transmission X Differential X Speed X 336/tire size. I compared it to a bunch of online calculators for rpm off the internet, and checked it against the charts after accounting for the .67 increase from OD.

Sorry for the long post, let the flammage begin for the Noobie, and thanks for any help you can give me :thumbup :beer
 

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green ones make me horny
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when i did the calculations on mine. the 302 with overdrive and running highway gears you would want 4.56s and for a little more power 4.88s. i would think 5.38s would be a little overkill
 

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Discussion Starter #4
MikE2 said:
with a 302 and overdrive 5.38's and 35's actually go very good together
Sweet, thats good to hear! Thanks for the input. I still have a couple weeks to decide as I just dropped most of my spare cash on the lift and tires. :duh
 

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imlikeojnow said:
when i did the calculations on mine. the 302 with overdrive and running highway gears you would want 4.56s and for a little more power 4.88s. i would think 5.38s would be a little overkill
You have an E4OD like mine, which has "better" gearing....in that the first gear is lower, something like 2.84 vs. 2.54 or so, and the AOD has more OD slightly, as in the stated .67 vs. our .71.

So with 35's I was fine with 4.10's and 351. While living in Colorado, 4.56 would have been much preferred. and with a 302, 4.56 OK and preferably 4.88, cept with the AOD given gearing I would think 4.88 or even 5.13.
 

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My set up.

Trandmission - e4od
Rear Axle - Sterling 10.25
Front Axle - Dana 60
Gears - 5.38:1 Yukon
Tires - 38.5 x 14.50 x 16.5 TLS SX
Actual tire height - 36.5" (tires at 1/2 tread or so)
PSI - 25
Motor - 351W
Speed - 65 MPH
RPM's - 2400
Bling factor - can "cherp" the tires from a stop
Milage - 6MPG city or hiway/3 gallons per mile in 4 low

If you are going to stay with a Dana 44 (ttb or SA) I would not recommend going any lower then 4:88's. The pinion gear gets really, really small once you drop to 5:13's.
 

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If you are going to stay with a Dana 44 (ttb or SA) I would not recommend going any lower then 4:88's. The pinion gear gets really, really small once you drop to 5:13's.

Zachtly.
 

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Discussion Starter #8
imlikeojnow said:
when i did the calculations on mine. the 302 with overdrive and running highway gears you would want 4.56s and for a little more power 4.88s. i would think 5.38s would be a little overkill
Ya I did come up with 4.56s being pretty close to stock. My problem is my truck seems undergeared even with the stock tires. It runs around 1800 at 65, but actually seems to use much less gas pedal at 75 around 2100 rpm's, putting me at 5.13s (if I want to cruise at 65 for best mpg). I just havn't figured out if this is typical or because I have engine performance issues. Apparently I am doing my calculations correctly. Sounds like yours pulls just fine at the lower rpm's and I don't want to go overkill with the gears to correct for a engine thats not running right. Oh but I want a little leeway in case I upgrade to 36 inch tires ;)
 

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Discussion Starter #9
dogonmut said:
My set up.

Trandmission - e4od
Rear Axle - Sterling 10.25
Front Axle - Dana 60
Gears - 5.38:1 Yukon
Tires - 38.5 x 14.50 x 16.5 TLS SX
Actual tire height - 36.5" (tires at 1/2 tread or so)
PSI - 25
Motor - 351W
Speed - 65 MPH
RPM's - 2400
Bling factor - can "cherp" the tires from a stop
Milage - 6MPG city or hiway/3 gallons per mile in 4 low

If you are going to stay with a Dana 44 (ttb or SA) I would not recommend going any lower then 4:88's. The pinion gear gets really, really small once you drop to 5:13's.
6 mpg :shocked oh well, I have the motorcycle. Alright I hadn't even considered this. So basically anything lower than a 4.88, and I'm looking at possibly shearing the pinion gear since i'll be running the stock ttb. Are there any expensive gears that can hold up at say 5.13? Anyone running 5.13 or 5.38 in their ttb w/o problems? Sounds like its best not to even take the chance.
 

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Shadofax said:
You have an E4OD like mine, which has "better" gearing....in that the first gear is lower, something like 2.84 vs. 2.54 or so, and the AOD has more OD slightly, as in the stated .67 vs. our .71.

So with 35's I was fine with 4.10's and 351. While living in Colorado, 4.56 would have been much preferred. and with a 302, 4.56 OK and preferably 4.88, cept with the AOD given gearing I would think 4.88 or even 5.13.

well smack my ass and call me sally. i didnt know all that.
 

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imlikeojnow said:
well smack my ass and call me sally.
Well ok "Smack" Sally.

I like my 4.56:1s and 35" tires with my AOD.
I wouldnt go any lower with 35"s than that.
 

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wakeav8b said:
6 mpg :shocked oh well, I have the motorcycle. Alright I hadn't even considered this. So basically anything lower than a 4.88, and I'm looking at possibly shearing the pinion gear since i'll be running the stock ttb. Are there any expensive gears that can hold up at say 5.13? Anyone running 5.13 or 5.38 in their ttb w/o problems? Sounds like its best not to even take the chance.
Just don't buy cheapies. Spicer does not make a gear for the D44 past I believe 4.10's. I know of 1 person running 5.13's, this should tell you a lot:



Hmmm, edit....strange it's not embedding the image. Here is the link to a D44 3.55 pinion vs. a 5.13:

http://www.supermotors.org/vehicles/registry/showmedia.php?id=75638
 

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I am running 5.13's on my pig, no issues. I would however go 5.38's if they made them for a 14 bolt.


When I had 38.5 and 4.56 that was a nice combo, but I did not have overdrive since I was running a sm465. Now with a nv4500 and my 41's, I like it the best because when I get up into the hills where 5th is just to low, than 4th is the perfect gear.

I understand that I have a chevy, and different tranny, but if you have overdrive than 5.38's with 35's you will have some nice off the line power, and plenty of room to go to a bigger tire later. That makes since to me since who really wants to spend the $$$$$ to change gears more than once.

Just my .02
 

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Shadofax said:
You have an E4OD like mine
i cannot add to this thread, as all the differential shit i have no experience with other than reading, but you are wrong on this.


wakeav8b has an AOD. look in the very first sentence in his second paragraph, his truck is also too old for the E4OD being a 1986.
 

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stepchild88 said:
i cannot add to this thread, as all the differential shit i have no experience with other than reading, but you are wrong on this.


wakeav8b has an AOD. look in the very first sentence in his second paragraph, his truck is also too old for the E4OD being a 1986.
No, I'm not. I'm like steve, I'm never wrong.:goodfinge

The post you took that from was in reply to:

Originally Posted by imlikeojnow

not wakeave8b.:toothless

Chvyboat, all that is nice, but kinda a moot point, since you have plenty of beef in your pinion to spare seeing as you are talking about a 14b, whereas the thread is focused on a D44 front. I'm sure you've seen how small that pinion is with 5.13gears.
 

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Shadofax said:
No, I'm not. I'm like steve, I'm never wrong.:goodfinge

The post you took that from was in reply to:

Originally Posted by imlikeojnow

not wakeave8b.:toothless

Chvyboat, all that is nice, but kinda a moot point, since you have plenty of beef in your pinion to spare seeing as you are talking about a 14b, whereas the thread is focused on a D44 front. I'm sure you've seen how small that pinion is with 5.13gears.

i'm sorry, didn't see who you quoted. you :twak me. :doh0715:
 

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Discussion Starter #17
Thanks for all the advice everyone :thumbup 5.38's seem definately out of the question as I can't find a manufacture that even makes them for the 8.8. They all seem to skip directly from 5.13s to 5.71s. I want to run the 5.13s, but after looking at that picture of how small that 5.13 pinion is, I may play it safe and go with the 4.88s. Time will tell when I go to order them :toothless
 
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