Rear end
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Junior User
Joined: Jun 1999
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Rear end
I need to buy a new rear end soon, but wanted to have your input as to what gear ratio to get. I want to have more torque off the line, the truck is used mainly in the city and rarly pulling anything. I read the tag on the rear end and it said DM 3V4 8CB
2 75 9 351 B
Anybody have any sugestions?
Its a 78 F-150 with a 302
Thank for your time,
Joe
2 75 9 351 B
Anybody have any sugestions?
Its a 78 F-150 with a 302
Thank for your time,
Joe
Junior User
Joined: Jun 1999
Posts: 90
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Rear end
This is just a suggestion but I would leave it just as it is and address the lack of power at the engine. Back when I had a '73 F100 I had a limited slip rear installed and decided it was a smart idea to go from 3.73 to 1 to the 4.10 to 1 ratio already in place in the limited slip. This turned out to be the dumbest thing I'd ever done to a vehicle. The gearing was ow way too low, in other words first gear was like a granny and required an immediate shift into second from the light. Freeway driving was pretty loud and I didn't to drive above 65 mph for fear of blowing the engine.
Soon after I paid for someone to bring me back the 3.73 and things were back to normal. You wouldn't think that ratios that close would make so much a difference.
One more thing, engine power is easier and cheaper to find. Rearends usually take some further mechanical ability - at least that's my opinion.
Soon after I paid for someone to bring me back the 3.73 and things were back to normal. You wouldn't think that ratios that close would make so much a difference.
One more thing, engine power is easier and cheaper to find. Rearends usually take some further mechanical ability - at least that's my opinion.
Fleet Owner
Joined: Jun 1999
Posts: 24,552
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From: Creedmoor, North Carolina
Rear end
Joe are you having trouble with the rearend now? You might go up to a 3.00 and still be OK. You will find the 3.00 in V8s with auto usually. 3.25 in V8s straight.
John
John
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Junior User
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Rear end
Yeah it is getting pretty worn, hasn't given me any problems yet but there is some play
Anyone know what ratio is in there now?, I just have a basic knowledge of this stuff. And that tag did not make any sense to me?.
Thanks
Joe
Anyone know what ratio is in there now?, I just have a basic knowledge of this stuff. And that tag did not make any sense to me?.
Thanks
Joe
Elder User
Joined: Aug 1999
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Rear end
It looks to me like your tag indicates a 2.75 ratio. That seems rather severe for a 302. My 302 had 3.5 and I wanted a higher ratio to lower freeway RPM. I put 31" tires and this helped some, if I replace the rear I am going to try 3.25
New User
Joined: Nov 1999
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Rear end
Joe,
I suggest that you look into Petersen's 4-Wheel & Off Road Magazine's December 1999 issue. In that issue is a section on gearing called "Gearing Cures". It starts on page 67.
You'll find lots of tips for installation, including some things that you might not think of during a normal ratio-swap.
As for your dillemma: according to your tag, you have 3.51:1 gears in the rear axle of your truck. This is normal for a 302ci motor. If you go with "high" (numerically lower) gears, you will get better launch, but sacrifice top end speed. If you go with "low" (numerically higher) gears, the opposite should happen. I would't recommend going any "higher" than 3.00:1 gears. Otherwise, you won't have any power on the highway.
The nice thing about your truck, though, is that it has a Ford 9" rear axle. This axle is fitted with a drop-out centersection, making gear swaps a breeze. Still, I would have it done by a professional drivetrain shop.
Hope this helps.
Sidewinder
1979 Ford F-350 Ranger XLT Crew-cab.
I suggest that you look into Petersen's 4-Wheel & Off Road Magazine's December 1999 issue. In that issue is a section on gearing called "Gearing Cures". It starts on page 67.
You'll find lots of tips for installation, including some things that you might not think of during a normal ratio-swap.
As for your dillemma: according to your tag, you have 3.51:1 gears in the rear axle of your truck. This is normal for a 302ci motor. If you go with "high" (numerically lower) gears, you will get better launch, but sacrifice top end speed. If you go with "low" (numerically higher) gears, the opposite should happen. I would't recommend going any "higher" than 3.00:1 gears. Otherwise, you won't have any power on the highway.
The nice thing about your truck, though, is that it has a Ford 9" rear axle. This axle is fitted with a drop-out centersection, making gear swaps a breeze. Still, I would have it done by a professional drivetrain shop.
Hope this helps.
Sidewinder
1979 Ford F-350 Ranger XLT Crew-cab.
New User
Joined: Nov 1999
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Rear end
Joe,
Another excellent gearing article is in Petersen's 4-Wheel & Off-Road's May 1998 issue.
Good luck.
Sidewinder
1979 F-350 Ranger XLT Crew-cab.
Another excellent gearing article is in Petersen's 4-Wheel & Off-Road's May 1998 issue.
Good luck.
Sidewinder
1979 F-350 Ranger XLT Crew-cab.
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Rear end
Try this. Jack up the rear of your truck, and put a chalk mark on the driveshaft. Rotate the rear wheel on complete revolution and count the number of turns the driveshaft makes. This will give you and idea of what your rearend ratio is. 3.08 seems to be a very common rearend out of the factory.
Junior User
Joined: Sep 1999
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Rear end
Depending on how much of a jump off the line you want and how much gas milage youre willing to sacrifice. If you're looking to race from stop light to stop light and not to concerned with gas milage then go with like a 350 or even a 370. Alot of people would say go to a 411 but if youve got a 3 speed tranny without overdrive then Id go no lower(higher in number) than a 370. If you are just looking for a little better jump and still want good highway driving milage then go with anything from a 350 to a 300 gear. Hope this helps.
Senior User
Joined: Aug 1999
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Rear end
I would think 3.50 or 3.70 gears would do fine in city traffic, giving ample off stop light starting power, without working your engine at open highway speeds. If interested, I will be changing the gearing in my 65 F-100, and will be willing to sell the 3.70 gears I currently have. E-mail me privately if interested, Joe.
Tim
Tim
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Junior User
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Rear end
Thanks for all the suggestions!
But....I have one more question......Would anyone reconmend having a limited slip or posi rear end. Where I live we get alot of snow in winter. Is one better than another for these type of conditions? and is it more expensive? I have a 2wd truck.
Joe
But....I have one more question......Would anyone reconmend having a limited slip or posi rear end. Where I live we get alot of snow in winter. Is one better than another for these type of conditions? and is it more expensive? I have a 2wd truck.
Joe