Need more low end torque

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Dec 14, 2012 | 09:16 PM

squirrel64

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Need more low end torque

Hey Guys
I have a 1985 F350 1ton 2wd 4 speed. I just recently swapped out a 6.9 diesel for a low mileage 7.3. I own a tree service and pull a chipper and full load of chips most of the time. Totaling 8000-9000 pounds My problem is that the new motor runs great but I'm still having problems with pulling on a grade. Especially starting out on a grade or hill. I wore my last clutch out doing so and I need to alleviate this problem.

I'm guessing it is geared too high in the rear. I don't need speed, I need grunt. I don't know what rear I have. I really don't know all that much when it come to rear end gears. Any help or suggestions would be appreciated

Dec 14, 2012 | 09:22 PM

Gary Lewis

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From: Northeast, OK

Hard to recommend something w/o knowing what you have now. Can you post a picture of the Cert Label on the door frame? It'll tell what axle ratio came out in the truck, although there's a chance that's been changed.

Or, put the rear on jack stands, mark one wheel, and turn the drive shaft by hand for 10 turns. How many full and partial turns did that wheel make?

Dec 14, 2012 | 09:26 PM

squirrel64

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Ok Gary, I'll try that Sunday when I get a break and report back

Dec 15, 2012 | 07:32 AM

Franklin2

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From: Virginia

Here are the possibilities. While you are looking, glance under the truck and see if you have a drain plug on the rear cover of the rearend, or if the cover is smooth with no drain plug.
SRW, Spicer 61-1, Cab & ch, 3.54 ratio
SRW, Spicer 61-1, Cab & ch, 3.73 ratio
SRW, Spicer 61-1, Cab & ch, 4.10 ratio
SRW, Spicer 61-1, Cab & ch, 4.56 ratio
SRW, Spicer 61-1, Pickup, 3.07 ratio
SRW, Spicer 61-1, Pickup, 3.54 ratio
SRW, Spicer 61-1, Pickup, 3.73 ratio
SRW, Spicer 61-1, Pickup, 4.10 ratio
SRW, Spicer 61-1, Pickup, 4.56 ratio
SRW, Spicer 70-U, Cab & ch, 3.54 ratio
SRW, Spicer 70-U, Cab & ch, 3.73 ratio
SRW, Spicer 70-U, Cab & ch, 4.10 ratio
SRW, Spicer 70-U, Cab & ch, 4.56 ratio
SRW, Spicer 70-U, Pickup, 3.54 ratio
SRW, Spicer 70-U, Pickup, 3.73 ratio
SRW, Spicer 70-U, Pickup, 4.10 ratio
SRW, Spicer 70-U, Pickup, 4.56 ratio
DRW, Cab & ch, (w/body code F37 & F38), Ford, 3.55 ratio
DRW, Cab & ch, (w/body code F37 & F38), Ford, 4.10 ratio
DRW, Cab & ch, (w/body code F37 & F38), Spicer, 10,000 GVW (70-U), 3.54 ratio
DRW, Cab & ch, (w/body code F37 & F38), Spicer, 10,000 GVW (70-U), 3.73 ratio
DRW, Cab & ch, (w/body code F37 & F38), Spicer, 10,000 GVW (70-U), 4.10 ratio
DRW, Cab & ch, (w/body code F37 & F38), Spicer, 10,000 GVW (70-U), 4.56 ratio
DRW, Cab & ch, (w/body code F37 & F38), Spicer, 11,000 GVW (70HD, 4.10 ratio)
DRW, Pickup, (w/o body code F37 & F38); Ford, 3.55 ratio
DRW, Pickup, (w/o body code F37 & F38); Ford, 4.10 ratio
DRW, Pickup, (w/o body code F37 & F38); Spicer, 3.54 ratio
DRW, Pickup, (w/o body code F37 & F38); Spicer, 3.73 ratio
DRW, Pickup, (w/o body code F37 & F38); Spicer, 4.10 ratio
DRW, Pickup, (w/o body code F37 & F38); Spicer, 4.56 ratio
SRW, Ford, 3.08 ratio
SRW, Ford, 3.55 ratio
SRW, Ford, 4.10 ratio

Dec 17, 2012 | 01:20 PM

squirrel64

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Driveshaft turn 10 times tire rotates 2 times exactly

No drain plug cover has 12 bolts

Tag on door states Trans-P Axle-69

EDIT............ I did this again with just one wheel of the ground. Turned the tire 2 complete turns and the driveshaft turned just a little over 3 1/2 turns

Dec 17, 2012 | 04:10 PM

Franklin2

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From: Virginia

Code 69 is a 3.55. I believe you have a Ford/Sterling rearend with 3.55 gears. Your easiest solution would be to round up a 4.10 rearend and install it. They are a very common ratio in these heavier trucks.

Code P for the trans is a 4 speed t19.

Where do you live? You can look up who has one on www.car-part.com.

Dec 17, 2012 | 04:55 PM

squirrel64

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Thanks Franklin. I talked with Brian at Randys Ring and Pinion and he also confirmed the 3.55 ratio and suggested a 4.10. So at least I have an idea of what will help me now.