Correct diff ratio required
Thread Starter
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Tuned
Joined: Sep 1999
Posts: 436
Likes: 32
From: Sonoita
Correct diff ratio required
G'day,
Hope someone out there can help. I have a 76 F100 with a 351 and C4. The motor is fairly new and runs on dedicated LPG administered thru a 2 barrel mixer. The diff ratio, as far as I can make out is about 2.7:1.
I have (believe this or not...) original sized wheels with 16 X R7.00 tyres. (Tall skinny commercial truck tyres...radials with ply ratings)
The problem is that I have pathetic take off. Could anyone tell me what the original diff ratio was, or if there was a range of ratios.?
Thanks
Marc
Hope someone out there can help. I have a 76 F100 with a 351 and C4. The motor is fairly new and runs on dedicated LPG administered thru a 2 barrel mixer. The diff ratio, as far as I can make out is about 2.7:1.
I have (believe this or not...) original sized wheels with 16 X R7.00 tyres. (Tall skinny commercial truck tyres...radials with ply ratings)
The problem is that I have pathetic take off. Could anyone tell me what the original diff ratio was, or if there was a range of ratios.?
Thanks
Marc
Fleet Owner
Joined: Jun 1999
Posts: 24,552
Likes: 74
From: Creedmoor, North Carolina
Correct diff ratio required
Marc, I suspect that the lp is your biggest source of sluggeishness. The 351W should have come with about 3.00 for a regular F100-150 & auto tranny. Remember if you change to a shorter gear it will burn more fuel while being snappy. There is a trade off.
With average rear prices $125.00 and seals, gear oil and new bearings (highly recomended by some) you can expect to change the gear for about $150-175.00 yourself.
John
jowilker
66 F100s
In the still cool hours of the night, you can hear chevys rusting away.
With average rear prices $125.00 and seals, gear oil and new bearings (highly recomended by some) you can expect to change the gear for about $150-175.00 yourself.
John
jowilker
66 F100s
In the still cool hours of the night, you can hear chevys rusting away.
Thread Starter
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Tuned
Joined: Sep 1999
Posts: 436
Likes: 32
From: Sonoita
Correct diff ratio required
Thanks John.
Forgot to mention too that it's Australian assembled and I imported it to New Zealand. Unfortunatly it will cost me significantly more to do. At $150 - $200 I'd have a couple with different ratios in the shed!!!
The LP isn't that bad. I would have heaps of trouble trying to get a gas tank for it, and gas is expensive ($1 / litre - equals about $4.50 / gallon)
Thanks again
M.
Forgot to mention too that it's Australian assembled and I imported it to New Zealand. Unfortunatly it will cost me significantly more to do. At $150 - $200 I'd have a couple with different ratios in the shed!!!
The LP isn't that bad. I would have heaps of trouble trying to get a gas tank for it, and gas is expensive ($1 / litre - equals about $4.50 / gallon)
Thanks again
M.
Fleet Owner
Joined: Jun 1999
Posts: 24,552
Likes: 74
From: Creedmoor, North Carolina
Correct diff ratio required
Marc I quoted the average southeren USA price for a 9 inch gear center section. If you already have the gears, then 3 quarts of gear oil and a gasket is all you would need to start.
Either way more pep = less mpg.
We are entering spring here, what season is it down under? :-)
John
jowilker
66 F100s
In the still cool hours of the night, you can hear chevys rusting away.
Either way more pep = less mpg.
We are entering spring here, what season is it down under? :-)
John
jowilker
66 F100s
In the still cool hours of the night, you can hear chevys rusting away.
Tuned
Joined: Apr 2000
Posts: 393
Likes: 3
From: Merrill
Correct diff ratio required
not used much here in Oregon,USA. I have only seen a few not many.
Scott
mickelsons(No Email Addresses In Posts!)
'98 Contour
'78 F-250 4X4 SC
'69 F-250 4X2
'52 International L-110
I would rather push a Ford than drive a chevy. (like you would have to push a ford. HA)
Scott
mickelsons(No Email Addresses In Posts!)
'98 Contour
'78 F-250 4X4 SC
'69 F-250 4X2
'52 International L-110
I would rather push a Ford than drive a chevy. (like you would have to push a ford. HA)
Fleet Owner
Joined: Jun 1999
Posts: 24,552
Likes: 74
From: Creedmoor, North Carolina
Correct diff ratio required
Lp is used very little as in the whole picture. Some fleets might use it, but it usually requires an additional large tank, that has to use good bed space, and that in itself make it undiserable, in my opinion. I must say that after reading this and another list, more trucks use it than I would have guessed.
I live in mid east coast USA, in North Carolina, I have only see one or two trucks that were using it, in my whole life.
John
jowilker
66 F100s
In the still cool hours of the night, you can hear chevys rusting away.
I live in mid east coast USA, in North Carolina, I have only see one or two trucks that were using it, in my whole life.
John
jowilker
66 F100s
In the still cool hours of the night, you can hear chevys rusting away.
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Senior User
Joined: Jun 1999
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Correct diff ratio required
You probably have a 2.75 axle ratio and coupled with those tall (30.4 inches) tires and LP won't get you moving very quickly at all. Instead of changing the gearing first, you could borrow a set of different tires to experiment. For every 2.5 inches in decrease in tire diameter, you would get the effect of moving 0.25 higher in the axle ratio. So going to a 28.0 tire (a 600x16) would give you effect of a 3.00 gear which probably would suit you. Of course, those 600x16s are even more than narrow. How about a new set of rims and rubber? Sorry about the english units but metric doesn't work for me.
Lee
1965 F100 short box styleside
Lee
1965 F100 short box styleside
Junior User
Joined: Mar 2000
Posts: 95
Likes: 0
Correct diff ratio required
If you tell me the axle codes , I'll tell you what it had from the factory, unless anyone changed the ratio, I can help you. look on the driver side door jamb, under the axle code, there are letters and numbers, reply with all the code and I'll give you the original body color, where the truck was made and the ratio(of course).
I hope I can be of some help, post the codes here and Ill check back tommorow about 4 O'clock and post the results here
SEANSTER 77' F150 XLT 2WD 400 C6
I hope I can be of some help, post the codes here and Ill check back tommorow about 4 O'clock and post the results here
SEANSTER 77' F150 XLT 2WD 400 C6
Thread Starter
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Tuned
Joined: Sep 1999
Posts: 436
Likes: 32
From: Sonoita
Correct diff ratio required
Hello to you both...
Lee, Thanks for the info on the tyre size to gear ratio, a handy little hint. It could prove difficult to borrow a set of wheels as F series trucks are almost as rare as rocking horse poo in this neck of the woods. Perhaps a large Ford sedan might have the correct stud pattern.
As for the new rims, I had some 15" wide rims with chunky off-road style tyres (about the same diameter as the tyres on it at the moment) but I found the steering to be very heavy with them.
Seanster, I had a look on the drivers door jam, and I see where there USED to be a sticker, near the striker plate, but the sticke is gone...As far as I'm aware, the engine was standard (it was a 302C, but I stroked it to 351 when I had it rebuilt late last year) It has a C4 auto, and the chap I brought it off said he changed the diff. So it's a bit of a hybred now...
But I do have another question for you. Can you tell me where the VIN would be tatooed on the body (or if it is...) I am about to take it through the certification process now, and apart from the VIN being on the Australian registration sticker on the window, I cannot find it stamped on the body.
Hope you all have a GREAT Easter.
Cheers
Marc
Lee, Thanks for the info on the tyre size to gear ratio, a handy little hint. It could prove difficult to borrow a set of wheels as F series trucks are almost as rare as rocking horse poo in this neck of the woods. Perhaps a large Ford sedan might have the correct stud pattern.
As for the new rims, I had some 15" wide rims with chunky off-road style tyres (about the same diameter as the tyres on it at the moment) but I found the steering to be very heavy with them.
Seanster, I had a look on the drivers door jam, and I see where there USED to be a sticker, near the striker plate, but the sticke is gone...As far as I'm aware, the engine was standard (it was a 302C, but I stroked it to 351 when I had it rebuilt late last year) It has a C4 auto, and the chap I brought it off said he changed the diff. So it's a bit of a hybred now...
But I do have another question for you. Can you tell me where the VIN would be tatooed on the body (or if it is...) I am about to take it through the certification process now, and apart from the VIN being on the Australian registration sticker on the window, I cannot find it stamped on the body.
Hope you all have a GREAT Easter.
Cheers
Marc
Senior User
Joined: Jun 1999
Posts: 222
Likes: 2
Correct diff ratio required
Any Ford 15" rim will work to try out a different wheel diameter. The only thing to look for is that the hub opening in the rim is large enough to get over your truck's axle hub. And since you know the rear gear set has been changed, look up the recent posting here in the forum about checking the ratio without pulling the axle shafts.
Lee
1965 F100 short box styleside
Lee
1965 F100 short box styleside
Senior User
Joined: Jun 1999
Posts: 222
Likes: 2
Correct diff ratio required
On the right side and ahead of the motor mount, you should find the VIN stamped into the top of the frame. Sometimes it ends up behind the motor mount. It should read from the right side of your truck. And many times it is faint so be ready to sand, brush or whatever down to bare metal to see it. For me, I then had to use white paint rubbed into the frame metal to get it to stand out enough for the motor vehicle folks to verify.
Lee
1965 F100 short box styleside
Lee
1965 F100 short box styleside
Elder User
Joined: Aug 1999
Posts: 910
Likes: 0
Correct diff ratio required
I've had Dodge wheels on my Ford 1/2 ton trucks before. Aside from Ford dogdish hubcabs not fitting, they work fine. Perhaps Dodges (Plymouth,Chryler) are rare too, but this might expand your options.
BBT
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