- Joined
- Dec 21, 2019
- Messages
- 45
Another 4R70W gearing question for those of you with experience. Bronco is not on the road yet, but I’m getting closer as I approach the 2 year mark.
What do ya’ll suggest as far as gearing?
Details:
Fully rebuilt 351W (0 miles)- full roller motor
Mild cam
ARF aluminum heads, Elderbrock RPM intake
Sniper 2 EFI
Rebuilt 4R70W w/rebuilt stock converter
Stock gearing 3.5
Planning to run 285/70/17 (32.7”).
USE: This will be a road only vehicle. Lots of on/off highway driving where I live (San Deigo)
Based on reading as many threads as I could find, it looks like 4.30, 4.56, or 4.88 are recommended. I’m trying to save money where possible and not overbuild, but also want to do things the right way once, as I seem to continually learn that lesson the hard way. Ugh.
Because of the 351W, I’m thinking I should move up to 31 spline rear axles, and at that point might as well do a Eaton truetrac rather than open carrier. Costs are snowballing quickly…
My plan was to just run as is (stock gearing) for a bit to see how things go, but I keep hearing with the current 3.50’s I will burn up the 4R70W as it hunts in/out of OD. I’d really hate to burn up a fresh trans. Also keep reading to just do the rear first and make sure its the right choice before doing the D44.
Which gears; 4.30, 4.56 , 4.88 or?
Bonus question: I’m learning/teaching myself as I go using this site, lots of research, and good ole YouTube videos. I’m sure I can get the 9” 3rd member removed along with axles etc, but I think the rear gear swap is beyond my skill level, certainly the D44 is. I’ve called around and prices for a swap are not easy to swallow. Anyone have a shop near Modesto, CA they recommend (bronco is in norcal currently)? Or do y’all recommend just buying a complete 3rd member online and slapping it in?
Numbers from GrimmJeeper. Left side is 4.56, right side is 4.88.
What do ya’ll suggest as far as gearing?
Details:
Fully rebuilt 351W (0 miles)- full roller motor
Mild cam
ARF aluminum heads, Elderbrock RPM intake
Sniper 2 EFI
Rebuilt 4R70W w/rebuilt stock converter
Stock gearing 3.5
Planning to run 285/70/17 (32.7”).
USE: This will be a road only vehicle. Lots of on/off highway driving where I live (San Deigo)
Based on reading as many threads as I could find, it looks like 4.30, 4.56, or 4.88 are recommended. I’m trying to save money where possible and not overbuild, but also want to do things the right way once, as I seem to continually learn that lesson the hard way. Ugh.
Because of the 351W, I’m thinking I should move up to 31 spline rear axles, and at that point might as well do a Eaton truetrac rather than open carrier. Costs are snowballing quickly…
My plan was to just run as is (stock gearing) for a bit to see how things go, but I keep hearing with the current 3.50’s I will burn up the 4R70W as it hunts in/out of OD. I’d really hate to burn up a fresh trans. Also keep reading to just do the rear first and make sure its the right choice before doing the D44.
Which gears; 4.30, 4.56 , 4.88 or?
Bonus question: I’m learning/teaching myself as I go using this site, lots of research, and good ole YouTube videos. I’m sure I can get the 9” 3rd member removed along with axles etc, but I think the rear gear swap is beyond my skill level, certainly the D44 is. I’ve called around and prices for a swap are not easy to swallow. Anyone have a shop near Modesto, CA they recommend (bronco is in norcal currently)? Or do y’all recommend just buying a complete 3rd member online and slapping it in?
Numbers from GrimmJeeper. Left side is 4.56, right side is 4.88.
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