Can someone tell me what the rear end ratio is on a Unique 427? Thanks
Can someone tell me what the rear end ratio is on a Unique 427? Thanks
Whatever you want it to be .
Seriously, that's set by the owner when you buy the kit. If you can get up under the rear of the car, there's a small (3/4" x 1+") metal tag that the rebuilder sets under one of the rear cover bolts - and the ratio is stamped into that tag, along with some other cryptic info.
Yeehah
For awhile most 427 cars with the FE series of engines had 3:31 gears. The buyer can specify what he wants. Butch Capps at Mid-South Gear in Knoxville does the differentals for Unique. He got a hold of several 3:42 gear sets and used them until they were depleated (not made anymore). The 3:54 gear sets are popular and now there has been a move by some folks to the 3:73. I ordered a 3:31 with my 427 side oiler 427 and a Top Loader close ratio. Was never happy with it so when I changed I went to the 3:73, wow you better have it pointed straight and both hands on the wheel, what a difference, that big block loves it.
Rick
427 S/C , 427 Side-oiler, 4 Speed Close Ratio Top Loader, 3:73 Gear
#4279405
Rick
I've though about doing the same thing.
What RPM are you turning in high gear at 70 MPH?
Jeff
Unique 427 S/C #4279451
Survival Motorsports FE482
4 Speed Toploader (Nascar close ratio)
3.31
I can answer that after this week-end....I have learned with the use of my GPS that my speedometer is 5.5 MPH fast with this gear. At 60MPH with the GPS I was showing nearly 66 MPH on the speedometer.
Rick
427 S/C , 427 Side-oiler, 4 Speed Close Ratio Top Loader, 3:73 Gear
#4279405
Nice evening yesterday so I did a nice little 60 mile loop through the back raods of Bourbon Country (Jim Beam, Makers Mark).
With the GPS showing true speed this is what I discovered;
Approximate
2900 RPM 60 MPH
3400 RPM 70 MPH
My engine likes the new gear, one thing I noticed to my suprise fuel consumption was pretty much equal to the 3:31 rear gear. The reason is probably because I wasn't moving back and forth from 3rd to 4th all the time.
At 70 MPH you can nail it in 4th and it walks the dog!!!
Rick
427 S/C , 427 Side-oiler, 4 Speed Close Ratio Top Loader, 3:73 Gear
#4279405
Calculate RPM for given Speed(MPH), Rear Gear Ratio and Trans Gear Ratio
Enter MPH: 70
Enter Tire Diameter: 26.5
Enter Rear Gear Ratio: :3.73
Enter Trans Gear Ratio: :1
Result -- RPM: 3310
http://golenengineservice.com/calc/calcrpm.htm
Brent
"Build em' light and wind em' tight!"
www.cardomain.com/ride/2660122
www.cardomain.com/ride/2659961
Sold Unique 427SC
#4279401
Thanks for your time and assistance.
I really like the 3:31 gear in my car (FIA). I had ordered a 3:54, but they were out of stock at the time Butch did the rear-end. Although the cam doesn't really smooth out until a little North of 2100 RPM, I have no problems running along in 4th or 5th gear.
Lighter cars don't seem to need as much gear as the heavier cars and with the taller rear ratio, I can use 1st gear when most can't. Even at the track I have found that the quicker cars are running anywhere from a 3:27 to 3:55 rear end ratios. Originally I would have thought it was the other way around and would have never known any different.
Justin