3.08 upgrade?

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3.08 upgrade?

HBF84
Bullnose Enthusiasts!  I would be grateful for some advice...  

I have a 1984 2x4 short bed with a 4.9 liter engine, the 4 speed manual transmission with overdrive, and a 3.08 rear end.  Can I change the ring and pinion to a 3.55, 3.73LD, 3.73HD, or 4.10 using the same housing?  Or to upgrade, do I need to find a whole new differential/axle assembly at a wrecking yard?  

The goal is to upgrade to increase towing capacity as much as possible.  I won't be towing too often but when I do, I would like to be able to tow as much as possible in lieu of buying a new truck!  Why buy a new truck when you can rock the bullnose down main street?!?

 
1984 F-150 2wd short bed with 4.9L, 4 speed overdrive manual transmission, and 3.08 rear end (18) switched to the 3.55 limited slip (H9).
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Re: 3.08 upgrade?

Nothing Special
Not sure what "LD" or "HD" is in that context, but yes, you can regear any axle to those ratios.  It's not easy (I've done it once, it took me about 5 weeks).  And if you have someone else do it (which I strongly recommend unless you KNOW you want to do it yourself) it ain't cheap.  Figure around $1000.  So often it's cheaper to find a new axle that has the gearing you want.  But then you'll have a junk yard axle of unknown quality, so you pays your money and takes your choice.

If you do regear you'll need to know what axle you have (or at least the shop that does it will need to know).  You can probably reuse your original differential (although some axles do require a different diff if you go past a certain point, called a "carrier break", that's often around 3.73, but will depend on what axle you have).

Or while you're regearing is a good chance to put a traction-aiding diff in if you want to do that.  It's the same labor to regear, replace a diff, or do both at the same time.  So if you;re going to do it, the same time is the right time so you only need to pay for the extra parts.  There are a lot of options that I think are a lot better than a factory limited slip, so if you do decide you want something other than what you have, do a little research before just getting a limited slip because you've heard they're better.
Bob
Sorry, no '80 - '86 Ford trucks
"Oswald": 1997 F-250HD crew cab short box, 460, E4OD, 4.10 gears
"Pluto": 1971 Bronco, 302, NV3550 5 speed, Atlas 4.3:1 transfer case, 33" tires
"the motorhome": 2015 E-450-based 28' class C motorhome, 6.8L V-10
"the Dodge": 2007 Dodge 2500, 6.7L Cummins
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Re: 3.08 upgrade?

Danny G
Nothing Special wrote
Not sure what "LD" or "HD" is in that context, but yes, you can regear any axle to those ratios.  It's not easy (I've done it once, it took me about 5 weeks).  And if you have someone else do it (which I strongly recommend unless you KNOW you want to do it yourself) it ain't cheap.  Figure around $1000.  So often it's cheaper to find a new axle that has the gearing you want.  But then you'll have a junk yard axle of unknown quality, so you pays your money and takes your choice.

If you do regear you'll need to know what axle you have (or at least the shop that does it will need to know).  You can probably reuse your original differential (although some axles do require a different diff if you go past a certain point, called a "carrier break", that's often around 3.73, but will depend on what axle you have).

Or while you're regearing is a good chance to put a traction-aiding diff in if you want to do that.  It's the same labor to regear, replace a diff, or do both at the same time.  So if you;re going to do it, the same time is the right time so you only need to pay for the extra parts.  There are a lot of options that I think are a lot better than a factory limited slip, so if you do decide you want something other than what you have, do a little research before just getting a limited slip because you've heard they're better.

Where you the one that was explaining diffs to me before? If so need to find those links, great info.
1986 F-150|Standard Cab|4x2|300Six|C6Transmission w/3.08 rear|Name:TBD
2021 Ranger XLT Super Crew
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Re: 3.08 upgrade?

Danny G
In reply to this post by HBF84
HBF84 wrote
Bullnose Enthusiasts!  I would be grateful for some advice...  

I have a 1984 2x4 short bed with a 4.9 liter engine, the 4 speed manual transmission with overdrive, and a 3.08 rear end.  Can I change the ring and pinion to a 3.55, 3.73LD, 3.73HD, or 4.10 using the same housing?  Or to upgrade, do I need to find a whole new differential/axle assembly at a wrecking yard?  

The goal is to upgrade to increase towing capacity as much as possible.  I won't be towing too often but when I do, I would like to be able to tow as much as possible in lieu of buying a new truck!  Why buy a new truck when you can rock the bullnose down main street?!?
Whatever gear size you go with, there was a thread also with a calculator that you could put your gearing into and your wheel size and get your optimum rear gear/rpm figured out for the tire size your want to use.
1986 F-150|Standard Cab|4x2|300Six|C6Transmission w/3.08 rear|Name:TBD
2021 Ranger XLT Super Crew
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Re: 3.08 upgrade?

Nothing Special
In reply to this post by Danny G
TheScatch wrote
Where you the one that was explaining diffs to me before? If so need to find those links, great info.
Yep, I was at least one doing that.  Here's the link to my thread on diffs on a different board.  I'm glad you found it helpful!
Bob
Sorry, no '80 - '86 Ford trucks
"Oswald": 1997 F-250HD crew cab short box, 460, E4OD, 4.10 gears
"Pluto": 1971 Bronco, 302, NV3550 5 speed, Atlas 4.3:1 transfer case, 33" tires
"the motorhome": 2015 E-450-based 28' class C motorhome, 6.8L V-10
"the Dodge": 2007 Dodge 2500, 6.7L Cummins
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Re: 3.08 upgrade?

Gary Lewis
Administrator
In reply to this post by Danny G
TheScatch wrote
Whatever gear size you go with, there was a thread also with a calculator that you could put your gearing into and your wheel size and get your optimum rear gear/rpm figured out for the tire size your want to use.
Not a thread but a page: Documentation/Driveline/Calculators.  It should let you figure out what RPM you'll be turning with any transmission, tire size, and rear gear combination.

But let's talk about transmissions.  None of the 4-speed OD transmissions were very heavy duty.  So if you want to tow very much you should consider changing out the transmission as that will be your weak link.

Unfortunately the Bullnose era was when the manufacturers were just seeing that they needed OD transmissions.  And they started introducing them in the light-duty trucks, only.  Then later in the decade the heavy-duty trucks started to get them.

So, if you want to tow heavy loads you should consider a heavier duty transmission.  But the ones that come out on these trucks, like the T-18/19 and the NP-435, do not have an overdrive so you'll hurt your MPG.  But the ZF5 from a later truck can allow you to tow heavy loads and it has an overdrive.  However, it is a truck transmission and it needs to be shifted S.L.O.W.L.Y.

You have a lot to think about.
Gary, AKA "Gary fellow": Profile

Dad's: '81 F150 Ranger XLT 4x4: Down for restomod: Full-roller "stroked 351M" w/Trick Flow heads & intake, EEC-V SEFI/E4OD/3.50 gears w/Kevlar clutches
Blue: 2015 F150 Platinum 4x4 SuperCrew wearing Blue Jeans & sporting a 3.5L EB & Max Tow
Big Blue: 1985 F250HD 4x4: 460/ZF5/3.55's, D60 w/Ox locker & 10.25 Sterling/Trutrac, Blue Top & Borgeson, & EEC-V MAF/SEFI

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Re: 3.08 upgrade?

Rembrant
In reply to this post by HBF84
HBF84 wrote
I have a 1984 2x4 short bed with a 4.9 liter engine, the 4 speed manual transmission with overdrive, and a 3.08 rear end.  Can I change the ring and pinion to a 3.55, 3.73LD, 3.73HD, or 4.10 using the same housing?  Or to upgrade, do I need to find a whole new differential/axle assembly at a wrecking yard?  
The gear ratio options you mentioned are available as are many others, assuming you have an 8.8 diff, which would have been standard in a 1984 2x4 short bed. I believe there are also 3.27 and 3.31 ratios available, and then many more above the ones you noted.

Nothing Special wrote
If you do regear you'll need to know what axle you have (or at least the shop that does it will need to know).  You can probably reuse your original differential (although some axles do require a different diff if you go past a certain point, called a "carrier break", that's often around 3.73, but will depend on what axle you have).
I seem to recall reading somewhere along the way that the 8.8 diff did not have a carrier break, but somebody can correct me if I'm wrong.
1994 F150 4x2 Flareside. 5.0 w/MAF, 4R70W, stock.
1984 F150 4X2 Flareside. Mild 302 w/ 5spd. Sold.
1980 F150 4X4 Flareside. 300i6 w/ 5spd. Sold in 2021.
1980 F100 4X2 Flareside. 351w/2bbl w/NP435. Sold in 1995

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Re: 3.08 upgrade?

Nothing Special
In reply to this post by Gary Lewis
Gary Lewis wrote
....  So, if you want to tow heavy loads you should consider a heavier duty transmission.  But the ones that come out on these trucks, like the T-18/19 and the NP-435, do not have an overdrive so you'll hurt your MPG.  But the ZF5 from a later truck can allow you to tow heavy loads and it has an overdrive.  However, it is a truck transmission and it needs to be shifted S.L.O.W.L.Y....
Gary, How does the ZF5 shifting compare to a T-18 or NP-435?  Those are the two reasonable truck transmissions I have experience with.  They don't shift like car transmissions, but I never found them too bad (other than not going into the non-synchro 1st until you stop).

But the absolute worst transmission I've ever had the displeasure to drive was the ZF-6 in my '08 F-250.  Several times in the less than one year I owned that truck I had to coast to a stop on the side of a highway because I couldn't get it into any gear while I was moving.  And it wasn't just me.  Everyone who drove that truck said it was the worst shifting trans they'd experienced.  The only "good" thing about it was that it was so bad that after being at the dealer for over 30 days of attempting to fix it Ford bought the truck back from me on a lemon-law claim (I didn't like a lot of things about the truck, so I was happy to be able to upgrade to an older truck without losing my shirt on resale of a truck I had bought new).

I want to go back to a manual trans sometime, and I'm wondering if the ZF-5 is enough better than the ZF-6 to consider.  But my front-runner right now is an NV-4500.


But back to HBF84, while swapping in an older heavy-duty 4 speed does mean you'll lose overdrive, that's not necessarily a bad thing for you.  I don't know what your current overdrive ratio is, but if it's 0.7:1 (which is fairly typical), that's a lot like changing your 3.08 axle gears to 4.4.  So just changing the trans might be all you need to do.


Bob
Sorry, no '80 - '86 Ford trucks
"Oswald": 1997 F-250HD crew cab short box, 460, E4OD, 4.10 gears
"Pluto": 1971 Bronco, 302, NV3550 5 speed, Atlas 4.3:1 transfer case, 33" tires
"the motorhome": 2015 E-450-based 28' class C motorhome, 6.8L V-10
"the Dodge": 2007 Dodge 2500, 6.7L Cummins
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Re: 3.08 upgrade?

Gary Lewis
Administrator
Bob - The three manuals I've owned and driven in these trucks, the NP435, T-19, & ZF5, have all driven pretty much the same - like truck transmissions.  By that I mean they don't want to be hurried in the shifting.  And, bear in mind that all three were well worn.  But I have a newly-rebuilt ZF5 about to go into Big Blue, so should have that experience to tell some time this year.

The only issue I thought I had with the ZF5 was bad synchros.  The 3rd gear ones were worn so you had to be really slow with it.  But that's the case with Big Blue's old T-19 as well.

Also, with the ZF5 it would some times not go into reverse until you moved the truck.  But that turned out to be a broken gear.

Otherwise the ZF5 was fine, albeit a bit noisier than the other two.
Gary, AKA "Gary fellow": Profile

Dad's: '81 F150 Ranger XLT 4x4: Down for restomod: Full-roller "stroked 351M" w/Trick Flow heads & intake, EEC-V SEFI/E4OD/3.50 gears w/Kevlar clutches
Blue: 2015 F150 Platinum 4x4 SuperCrew wearing Blue Jeans & sporting a 3.5L EB & Max Tow
Big Blue: 1985 F250HD 4x4: 460/ZF5/3.55's, D60 w/Ox locker & 10.25 Sterling/Trutrac, Blue Top & Borgeson, & EEC-V MAF/SEFI

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Re: 3.08 upgrade?

Nothing Special
Gary Lewis wrote
Bob - The three manuals I've owned and driven in these trucks, the NP435, T-19, & ZF5, have all driven pretty much the same - like truck transmissions....
"Like truck transmissions" doesn't scare me.  But when a friend (who drove a Dodge with the HEAVY NV5600) drove my '08 and had to crawl off a higher speed section road in 1st gear because he couldn't get it to upshift, that makes me leary of a manufacturer!  (That friend had wanted to drive my truck because he couldn't believe it was as bad as I said.  After driving it he said I was being to kind to it, it was way worse than I was saying.)
Bob
Sorry, no '80 - '86 Ford trucks
"Oswald": 1997 F-250HD crew cab short box, 460, E4OD, 4.10 gears
"Pluto": 1971 Bronco, 302, NV3550 5 speed, Atlas 4.3:1 transfer case, 33" tires
"the motorhome": 2015 E-450-based 28' class C motorhome, 6.8L V-10
"the Dodge": 2007 Dodge 2500, 6.7L Cummins
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Re: 3.08 upgrade?

Ford F834
Administrator
I have not driven a ZF6, but this is not the first negative comment I’ve heard regarding how it shifts. The ZF-5 that Jan and I put in his ‘86 F250 shifted very well. It has a long throw and does not change gears quickly, but was a pleasure. In the desert with the ambient temperature at 110*F it had that gear rollover clatter that most diesel owners report, but Jan says that isn’t as bad since he changed fluid. My particular T19 is probably the nicest shifting truck transmission I’ve ever used. It is almost car-like, and very smooth. I would prefer this over the ZF except for the lack of overdrive and the smaller input shaft is not strong enough for the engine I am building. I have not owned or driven a NV series transmission, but what I have heard is that they are inferior to the ZF5.

To the original poster of this thread, I would second the suggestion for a stouter transmission before going lower on the axle gears. Then if you really need it, reduce the axle ratio. I have the close ratio T19 with 3.00 axles gears and I love mine. I pull approximately 5,000 lb trailer with it.
SHORT BED 4-DOOR DIESEL: 1986 F350 4x4 under construction-- 7.3 IDIT ZF5+GVOD

STRAIGHT SIX 4X4: 1981 F150 2wd to 4x4-- 300 I6 close ratio diesel T19, hydroboost brakes, Saginaw steering

BIG F: 1995 F-Superduty under construction— converting to 6.9L IDI diesel ZF5+DNE2
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Re: 3.08 upgrade?

Gary Lewis
Administrator
I think you two have suggested a good approach - a stouter tranny with the existing rear gears.  You should easily be able to do such a tranny for the price of new gears, and to tow very much the tranny will need to be changed anyway.  Then, if the rear gears don't cut after trying the combo out, it change them as well.

But if it was me, I think I'd look for a ZF5.  I say that because, using the calculator and assuming 235/75-15 tires, the engine will be turning ~1800 RPM at 65 in 5th with the 3.08's.  That's just about right to get good MPG when not towing.  And when towing it would be turning ~2300 RPM in 4th, which is also about right.
Gary, AKA "Gary fellow": Profile

Dad's: '81 F150 Ranger XLT 4x4: Down for restomod: Full-roller "stroked 351M" w/Trick Flow heads & intake, EEC-V SEFI/E4OD/3.50 gears w/Kevlar clutches
Blue: 2015 F150 Platinum 4x4 SuperCrew wearing Blue Jeans & sporting a 3.5L EB & Max Tow
Big Blue: 1985 F250HD 4x4: 460/ZF5/3.55's, D60 w/Ox locker & 10.25 Sterling/Trutrac, Blue Top & Borgeson, & EEC-V MAF/SEFI