August B/S Thread
Elder User
Joined: Jul 2007
Posts: 842
Likes: 1
From: Salem, CT
Dave,
Another thing you will find out is some differentials will support (for example) 4.88 and up and some will support 4.88 and down. So you may need to change you differential to get the gearing you want.
Hi Aaron:
The van has 4.10 in an open differential in the rear and I'm not sure what differential in the front.
As for what gearing am I aiming for, I'm still researching that.
I am leaning toward increasing my torque to the road which will cost me fuel economy with the intent of later installing an under-drive auxiliary transmission so that I'll get better gas milage that I get now.
Based on a gearing calculator:
Going from OEM to Michelin 285/70R/19.5 with the OEM 4.10 rear-end
produces an effctive 3.53:1 Ratio.
That equates to two rear-ends lower, i.e. 3.73 followed by 3.55.
At 65 MPH with the 30.5" diameter OEM tires and transmission in 5th gear, the engine is running at 2084.5 RPM.
At 65 MPH with the 35.4" diameter Michelin 285/70R/19.5 tires and the transmission in 5th gear, the engine is running at 1795.9 RPM (about 14% less RPMs).
__________________________________________________ _
To re-achieve the OEM torque to the road then would need a 4.76:1 rear-end.
Ford's next up rear-end is a 4.88.
For greater torque to the road then go with a 5:19:1 rear-end.
Ford's highest rear-end is 5.13.
A compromise between OEM torque to the road and the effective ratio would be a 4.33:1 rear-end.
Ford offers a 4.63 rear-end.
U.S. Gear Corp's 1.25:1 under-drive unit in UD would provide an effective 4.4125 rear-end
-AND-
Can handle Compression-Braking, i.e. an
exhaust back-pressure brake
Gear Vendors's 1.28:1 under-drive unit in UD would provide an effective 4.52 rear-end
-But-
Can NOT handle Compression-Braking, i.e. NO
exhaust back-pressure brake
Another thing you will find out is some differentials will support (for example) 4.88 and up and some will support 4.88 and down. So you may need to change you differential to get the gearing you want.
Hi Aaron:The van has 4.10 in an open differential in the rear and I'm not sure what differential in the front.
As for what gearing am I aiming for, I'm still researching that.
I am leaning toward increasing my torque to the road which will cost me fuel economy with the intent of later installing an under-drive auxiliary transmission so that I'll get better gas milage that I get now.
Based on a gearing calculator:
Going from OEM to Michelin 285/70R/19.5 with the OEM 4.10 rear-end
produces an effctive 3.53:1 Ratio.
That equates to two rear-ends lower, i.e. 3.73 followed by 3.55.
At 65 MPH with the 30.5" diameter OEM tires and transmission in 5th gear, the engine is running at 2084.5 RPM.
At 65 MPH with the 35.4" diameter Michelin 285/70R/19.5 tires and the transmission in 5th gear, the engine is running at 1795.9 RPM (about 14% less RPMs).
__________________________________________________ _
To re-achieve the OEM torque to the road then would need a 4.76:1 rear-end.
Ford's next up rear-end is a 4.88.
For greater torque to the road then go with a 5:19:1 rear-end.
Ford's highest rear-end is 5.13.
A compromise between OEM torque to the road and the effective ratio would be a 4.33:1 rear-end.
Ford offers a 4.63 rear-end.
U.S. Gear Corp's 1.25:1 under-drive unit in UD would provide an effective 4.4125 rear-end
-AND-
Can handle Compression-Braking, i.e. an
exhaust back-pressure brake
Gear Vendors's 1.28:1 under-drive unit in UD would provide an effective 4.52 rear-end
-But-
Can NOT handle Compression-Braking, i.e. NO
exhaust back-pressure brake
Elder User
Joined: Jul 2007
Posts: 842
Likes: 1
From: Salem, CT
Dave,
I got my stuff from http://www.ringpinion.com/ very good priceing and good and fast service.
I got my stuff from http://www.ringpinion.com/ very good priceing and good and fast service.
Well I just discovered that just the gears are pricey, ouch.
I have come to believe that my gearing choices are controlled by what is available in a reverse cut for the front axle.
Am I mistaken, can a 4x4 front axle not need reverse cut gears?
Since I have a Dana 70 rear and 60 front, besides the 4.10 that I have, the next reverse cut gear for the 60 is the 4.88.
Now the 4.88 is sweet because the calculator predicts that for the 35.4" tires I would need a 4.76 to match the revs per mile of the original 30.5" tires.
The 60 axle doesn't have any reverse cut gears above the 4.88.
The 60 axle has reverse cut gears in 3.73 & 3.54 which match up with those for the 70 axle.
More thought for tomorrow.
I have come to believe that my gearing choices are controlled by what is available in a reverse cut for the front axle.
Am I mistaken, can a 4x4 front axle not need reverse cut gears?
Since I have a Dana 70 rear and 60 front, besides the 4.10 that I have, the next reverse cut gear for the 60 is the 4.88.
Now the 4.88 is sweet because the calculator predicts that for the 35.4" tires I would need a 4.76 to match the revs per mile of the original 30.5" tires.
The 60 axle doesn't have any reverse cut gears above the 4.88.
The 60 axle has reverse cut gears in 3.73 & 3.54 which match up with those for the 70 axle.
More thought for tomorrow.
Moderator
Joined: May 2007
Posts: 158,556
Likes: 12,040
From: Greenfield, MA
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pedant
Joined: Jan 2008
Posts: 23,576
Likes: 40
From: EXTREME southwest CT
I know I needed a 4.10 carrier when I grenaded my R&P.
Elder User
Joined: Jul 2007
Posts: 842
Likes: 1
From: Salem, CT
I think it depends on the carrier housing and the differential. That's why I said 'for example'.
Logistics Pro
Joined: Oct 2003
Posts: 4,058
Likes: 2
From: Connecticut
Is that the one in Newington somewhere? I've been debating taking a ride over there at some point to do a walk through. Its been years since I've actually be allowed in a junkyard. Do they let you remove your own parts as well?
Senior User
Joined: Oct 2005
Posts: 389
Likes: 0
From: Berlin, CT USA
its chuck n eddies in southington, you pay 1$ at the little building and walk around for as long as you want to find what you need, and yes you take the parts out yourself, i love this place. When i used to have my 87 they came in handy. I plowed into 34 carriages and messed my front end, and i got 2 headlight units(whole thing) a small pieces of trim above the bumper, new grille all for bout 75$ and 3 hrs of work ha.