Ring and Pinion Recommendations
Thread Starter
|
Three Wheeling
Joined: Jan 2019
Posts: 76
Likes: 6
Ring and Pinion Recommendations
I just purchased front and rear Ashcroft air lockers, and I would like to upgrade ring and pinion to at the same time. The truck is a V8 (4.0) petrol Discovery 2. With a safety devices roof rack, lights, and 55lb synthetic winch. Bumpers are steel but designed to be lighter weight than ARB etc. I travel as light as possible so recovery gear/luggage weight is <200lbs+driver+passenger weight. I am currently on 285/75/16 m/t and stock 3.54 gearing and 1.21 transfer case. Which gives me trouble twice a year when I head up to the taller mountains on paved roads(working the engine and transmission slightly more than I’d like) and occasionally on decent grades keeping with the flow of traffic, otherwise gearing is mostly ok. I do about 60% highway, approx speed is 80mph (120kmh), 20% side road, and 20% technical off-road trail driving. I would like to change to 315/75/16 m/t tires within the year (I probably wouldn’t switch back to 285/75, unless the 315/75’s are unlivable. I do not tow, this is not my daily driver, and I would like to keep as good as fuel economy as possible (please no comments on 35s and economy, theres a reason we aren’t all rocking the oem 29’s) I drive it twice a week to work (112km round trip, at an average speed of 120kmh) with addition of overland/off-road trips from 100-500km every other month.
What are your recommendations for a ring and pinion?
Thank you!
What are your recommendations for a ring and pinion?
Thank you!
Camel Trophy
Joined: Aug 2014
Posts: 4,743
Likes: 985
From: Southwestern Virginia
If anyone sells a 4.30 gear, I'd go for that with a 35. I ran the 285s for a while with a hopped up 4.6 and it was drivable, but it wasn't great. I'd actually guess you'd pick up some fuel economy with a lower gear.
If nobody sells a 4.30 I'd go for a 4.56 all day long.
If nobody sells a 4.30 I'd go for a 4.56 all day long.
Pro Wrench
Joined: May 2016
Posts: 1,617
Likes: 184
From: Lake Tahoe
Nice. I've love to get some ashcroft lockers in the future. I'd use the ratio calculator on ashcroft: https://www.ashcroft-transmissions.c...atio_calc.html
Tire sizes are rarely to spec...a 315/75r16 (34.6" spec) is probably going to be between 33-34" in reality. Given that, 4.12 should be the right gear. 4.56 would work, but I think the revs will be a little too high, and fuel economy will suffer
https://www.ashcroft-transmissions.c...-4-12-r-p.html
I have 1.41 gears in my transfer box, and I'd like to go to 315/75 as well. I'll probably use 3.75 gears.
Tire sizes are rarely to spec...a 315/75r16 (34.6" spec) is probably going to be between 33-34" in reality. Given that, 4.12 should be the right gear. 4.56 would work, but I think the revs will be a little too high, and fuel economy will suffer
https://www.ashcroft-transmissions.c...-4-12-r-p.html
I have 1.41 gears in my transfer box, and I'd like to go to 315/75 as well. I'll probably use 3.75 gears.
Camel Trophy
Joined: Aug 2014
Posts: 4,743
Likes: 985
From: Southwestern Virginia
If I go bigger than factory, I always go lower than factory because you're not only increasing size but also increasing rolling weight. And in my experience, lower gear ratios actually get better gas mileage than higher ones except where all out highway cruising is concerned, and sometimes even then. I have an '01 Mustang GT with 4.11 gears that'll get 26 mpg highway all day long. Rated at 23 from the factory.
Of course there are other factors such as how much gear you haul and what size engine you've got.
Also, sorry to hear about your break in, Jeff. Hope you didn't lose much and that you're getting that sorted.
Of course there are other factors such as how much gear you haul and what size engine you've got.
Also, sorry to hear about your break in, Jeff. Hope you didn't lose much and that you're getting that sorted.
Thread Starter
|
Three Wheeling
Joined: Jan 2019
Posts: 76
Likes: 6
Very helpful info. It’s difficult to compare other cars/trucks to ours because the discos transfer case is 1.22:1 not 1:1 so it’s apples to oranges. Also depends on the final drive of the transmission which is .73 on the automatic disco 2’s. On a side note, I’m still sort of on the fence with 35s. And it would be nice to go with a ratio that will also work for 33s incase I want to switch back. But on the other hand, I don’t won’t to be in the same boat I’m in now (too tall a gear) except with 35’s and $750 in gears.
From the gear ratio calculator here are some numbers:
255/65/16 and 3.54 (factory 29’s)
2532rpms @ 70mph
2712rpms @ 75mph
2893rpms @ 80mph
255/70/16 and 3.54 (30’s, common on stock discos)
2467rpms @ 70mph
2643rpms @ 75mph
2819rpms @ 80mph
285/75/16 and 3.54 (my current 33’s):
2240rpms @ 70mph
2400rpms @ 75mph
2560rpms @ 80mph
315/75/16 and 4.12 (35s)
2474rpms @ 70mph
2651rpms @ 75mph
2827rpms @ 80mph
315/75/16 and 4.37
2624rpms @ 70mph
2811rpms @ 75mph
2999rpms @ 80mph
From the gear ratio calculator here are some numbers:
255/65/16 and 3.54 (factory 29’s)
2532rpms @ 70mph
2712rpms @ 75mph
2893rpms @ 80mph
255/70/16 and 3.54 (30’s, common on stock discos)
2467rpms @ 70mph
2643rpms @ 75mph
2819rpms @ 80mph
285/75/16 and 3.54 (my current 33’s):
2240rpms @ 70mph
2400rpms @ 75mph
2560rpms @ 80mph
315/75/16 and 4.12 (35s)
2474rpms @ 70mph
2651rpms @ 75mph
2827rpms @ 80mph
315/75/16 and 4.37
2624rpms @ 70mph
2811rpms @ 75mph
2999rpms @ 80mph
Last edited by Dsport; Mar 8, 2019 at 01:29 AM.
Thread
Thread Starter
Forum
Replies
Last Post