Working on AWD project, some of you are already familiar.
After initially swinging toward a TR-6060 based driveline, my needle has swung back to a BMW driveline using a franken GS6-53BZ with ATC-700 T-case from E70 X5.
The TR-6060 with 0.56:1 sixth and 3.64 diffs gave a fairly nice highway cruise gear with 2.04 overall ratio. Engine will be S62, so low rpm torque will be plentiful. With stock diameter tires, this should result in 1700 RPM at 60 and 2300 at 80. Not bad. Not as good as an LS1 Camaro, but not bad.
To get the same overall ratio with the GS6-53BZ, I'd need to run 2.35 diffs. Even if I can use a diesel 6th in the gas transmission, I'd still need a 2.56 or so.
*Maybe* if I can track down ZF service information for the transmission, I *might* be able to swap in the diesel 6th gear. The gas sixth is 0.87, while the diesel 6th is 0.84. That doesn't sound like much, BUT the diesel box likely has a shorter input to counter shaft ratio, which could make the actual 6th gear mesh much taller once swapped into the gas box. But that's not something to count on until I have tooth counts.
Since I have to split the transmission ANYWAY to put the V8 bellhousing on the AWD 6 cylinder transmission, it would be handy to swap the gear, if feasible. For now I'll continue as though I'll have to keep the gas 6th.
Since I'm running an S62, I have to use the E53 AWD oil pan. Using the E53 pan means I have to use the E53 front diff case. Euro E53's had ratios down to 3.07. The 3.07 diff uses the "tall ratio" case which has more clearance inside for a larger pinion. This case will be necessary in order to use the taller ratios I'm looking at.
Also in my possession I have the large case 2.93 LSD from an E23 745i turbo. It bolts up to the E30 subframe.
Is service infomation (pinion depth, preload torque, etc.) available for the front diffs? Shims? I @$$ume I'll be able to get new bearings and pinion seal based on part marks.
Option A):
E53 3.07 front case + 2.35 E46 front gears (+ Quaife?), ordered from ebay.de or ebay.co.uk
2.35 rear end... not sure this was ever put into an E30 style case.
Pros: Tall enough top gear for good cruise, yet first gear still >10:1, so maintain good low speed acceleration and holeshot.
Cons: I want a 210mm rear
Requires: Two front diffs and a 188 rear diff shipped from Europe; building a front diff with no service information.
Option B):
E53 3.07 front case + 2.93 E46 gears (+Quaife?) + 2.93 large case rear already in my possession.
This results in a 2.55:1 overall top gear. That's 25% more RPM on the highway than the 2.04:1 benchmark. With stock sized tires, that's 2150 at 60mph, which is pretty short. That's 2900 at 80. I already drive that in my V8 Fiero... it's gross overkill and wasteful, especially with a 6 speed.
Pros: cheap, only ship two diffs from Europe; large case rear
Cons: Way shorter gearing than I want
Requires: shipping two front diffs from Europe; building a front diff without service information and setting up axles for 94mm rear CV joints.
Option C):
E53 3.07 front case + 2.64 gears from a later model car with N series engine + a 2.65 large case rear. These aluminum case front diffs come from the same era during which BMW started welding the ring gears to the carriers in the rear diffs. I don't know if the ring and carrier are welded in the front diff. I don't know if the ring & pinion will transfer to the older case, and I don't know if I might have to do something crazy like machine the gear off the carrier and drill/tap it to bolt to the older carrier.
Pros: better ratio than option B; 210mm rear
Cons: Huge technical unknowns; may not be feasible/possible
Requires: Shipping two front diffs from Europe and finding a 210mm 2.65 gear set stateside; building a first of kind front diff with no service information
Option A sounds the most reasonable as it gives me the gears I want, and the 188 rear diff with the 94mm CV's is actually strong enough for the power I want to put through it. I'm just into overkill and like the unbreakable 210mm, plus the oddball large case that bolts into the E30 appeals to me, just because it's a weird rare part.
Thoughts on front diff parts? gear options? anything else?
After initially swinging toward a TR-6060 based driveline, my needle has swung back to a BMW driveline using a franken GS6-53BZ with ATC-700 T-case from E70 X5.
The TR-6060 with 0.56:1 sixth and 3.64 diffs gave a fairly nice highway cruise gear with 2.04 overall ratio. Engine will be S62, so low rpm torque will be plentiful. With stock diameter tires, this should result in 1700 RPM at 60 and 2300 at 80. Not bad. Not as good as an LS1 Camaro, but not bad.
To get the same overall ratio with the GS6-53BZ, I'd need to run 2.35 diffs. Even if I can use a diesel 6th in the gas transmission, I'd still need a 2.56 or so.
*Maybe* if I can track down ZF service information for the transmission, I *might* be able to swap in the diesel 6th gear. The gas sixth is 0.87, while the diesel 6th is 0.84. That doesn't sound like much, BUT the diesel box likely has a shorter input to counter shaft ratio, which could make the actual 6th gear mesh much taller once swapped into the gas box. But that's not something to count on until I have tooth counts.
Since I have to split the transmission ANYWAY to put the V8 bellhousing on the AWD 6 cylinder transmission, it would be handy to swap the gear, if feasible. For now I'll continue as though I'll have to keep the gas 6th.
Since I'm running an S62, I have to use the E53 AWD oil pan. Using the E53 pan means I have to use the E53 front diff case. Euro E53's had ratios down to 3.07. The 3.07 diff uses the "tall ratio" case which has more clearance inside for a larger pinion. This case will be necessary in order to use the taller ratios I'm looking at.
Also in my possession I have the large case 2.93 LSD from an E23 745i turbo. It bolts up to the E30 subframe.
Is service infomation (pinion depth, preload torque, etc.) available for the front diffs? Shims? I @$$ume I'll be able to get new bearings and pinion seal based on part marks.
Option A):
E53 3.07 front case + 2.35 E46 front gears (+ Quaife?), ordered from ebay.de or ebay.co.uk
2.35 rear end... not sure this was ever put into an E30 style case.
Pros: Tall enough top gear for good cruise, yet first gear still >10:1, so maintain good low speed acceleration and holeshot.
Cons: I want a 210mm rear
Requires: Two front diffs and a 188 rear diff shipped from Europe; building a front diff with no service information.
Option B):
E53 3.07 front case + 2.93 E46 gears (+Quaife?) + 2.93 large case rear already in my possession.
This results in a 2.55:1 overall top gear. That's 25% more RPM on the highway than the 2.04:1 benchmark. With stock sized tires, that's 2150 at 60mph, which is pretty short. That's 2900 at 80. I already drive that in my V8 Fiero... it's gross overkill and wasteful, especially with a 6 speed.
Pros: cheap, only ship two diffs from Europe; large case rear
Cons: Way shorter gearing than I want
Requires: shipping two front diffs from Europe; building a front diff without service information and setting up axles for 94mm rear CV joints.
Option C):
E53 3.07 front case + 2.64 gears from a later model car with N series engine + a 2.65 large case rear. These aluminum case front diffs come from the same era during which BMW started welding the ring gears to the carriers in the rear diffs. I don't know if the ring and carrier are welded in the front diff. I don't know if the ring & pinion will transfer to the older case, and I don't know if I might have to do something crazy like machine the gear off the carrier and drill/tap it to bolt to the older carrier.
Pros: better ratio than option B; 210mm rear
Cons: Huge technical unknowns; may not be feasible/possible
Requires: Shipping two front diffs from Europe and finding a 210mm 2.65 gear set stateside; building a first of kind front diff with no service information
Option A sounds the most reasonable as it gives me the gears I want, and the 188 rear diff with the 94mm CV's is actually strong enough for the power I want to put through it. I'm just into overkill and like the unbreakable 210mm, plus the oddball large case that bolts into the E30 appeals to me, just because it's a weird rare part.
Thoughts on front diff parts? gear options? anything else?
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