mountainhick
Member
Figured I'd share a work in progress. I am just getting started and value input!
With a few minor differences I am playing along with Luthj converting my van to 4wd. I was salivating over the ARB front locker he installed, but after consideration decided I'd try something different, and it is a unique enough project I reckon it deserves to be it's own topic. The ARB air locker with compressor is just too much $$ on top of the rest of the 4wd conversion, and to me a rear locker is more useful. It turns out I can accomplish this much more cheaply, though it will take significantly more work hours.
Since the 4wd part of the project is based on GMT 800 series front end, and GM 8 bolt wheels, this was my starting point looking for rear axle options.
I went into it somewhat naively not knowing all the permutations of GM 8 bolt rear axles and quickly found a GM 14 bolt 9.5" rear on a 2003 Chevy Silverado in a u pull junk yard with proper 3.73 gear ratio, has a G80 gov lock, and looked in very good shape except for a little too easy preload and a bit too much backlash. I opened the rear cover while still on the vehicle and the ring gear looks very good, so I figure it will probably be fine with pinion preload and backlash reset. I pulled it and brought it home for $138
Note: the gov lock isn't the greatest, but for the price it's something at least to start with, and the GM diffs can all be upgraded with other options. So I'll go with it for now and see how it performs.
So, the naive aspect was I did not know that there are multiple versions of 14 bolt GM rear axles. The biggest differences are:
9.5" ring gear, semi floating axle. GM 2500 series. This one has a different sized diff case and different rear cover which can be identified by it's rounder shape. It is not quite as heavy duty as the full floaters, but should be plenty adequate for the Sprinter. It is a pretty large increase in ring and pinion size, and the axles and tubes are heavier.
10.5 ring gear, full floating axle. GM 2500 HD series identified by larger diff housing, more angular diff cover, full floating axle bearing protruding through wheel center with bolted on cap, and pinion mounted into a bearing/hub assembly that bolts into the diff housing
11.5" ring gear full floating axle GM 2500HD-3500 series has all the same attributes as the 10.5 except the pinion gear does not have the additional hub which mounts to the housing, rather having bearings mount directly into the diff housing
Some of them apparently started having ABS sensors in 2006, but back to around the beginning of the GMT800 series, the rear ABS function was based only on rear axle speed, not independent wheel speeds for each rear wheel. This was accomplished with a speed sensor at the output shaft of T case or transmission.
There is a kit for adding wheel sensors and tone rings on the 10.5 axle: https://www.artecindustries.com/abs_kit_14b But these rings do not have a number of teeth that easily multiplies/divides in order to manipulate for inputting into the Sprinter's ESP computer. The ideal would be to have a set cut with with 44 teeth.
Likewise, another aspect like with Luthj's 4wd conversion is if you use a GM rear that does have independent sensors, they are 55 tooth (vs T1N's 44 tooth so frequency needs to be corrected before signal is sent to Sprinter ESP/ABS system. This is more mathematically desirable that the kit above since 55 is divisible by the integer 11, not a repeating decimal. We both are already using an arduino based circuit to correct the front wheel speed frequencies from the 55 tooth rings, so it would be do-able to use the same circuit for rear wheels, but if 44 tooth tone rings could be used, so much the better.
Another problem looking at more recent GM axles is that somewhere around 2011 wheel bolt circle diameter went from 156mm to 180mm.
So after realizing I may have set myself up for failure with the 9.5" axle I purchased, I sought options to add sensors to play well with the Sprinter.
With a few minor differences I am playing along with Luthj converting my van to 4wd. I was salivating over the ARB front locker he installed, but after consideration decided I'd try something different, and it is a unique enough project I reckon it deserves to be it's own topic. The ARB air locker with compressor is just too much $$ on top of the rest of the 4wd conversion, and to me a rear locker is more useful. It turns out I can accomplish this much more cheaply, though it will take significantly more work hours.
Since the 4wd part of the project is based on GMT 800 series front end, and GM 8 bolt wheels, this was my starting point looking for rear axle options.
I went into it somewhat naively not knowing all the permutations of GM 8 bolt rear axles and quickly found a GM 14 bolt 9.5" rear on a 2003 Chevy Silverado in a u pull junk yard with proper 3.73 gear ratio, has a G80 gov lock, and looked in very good shape except for a little too easy preload and a bit too much backlash. I opened the rear cover while still on the vehicle and the ring gear looks very good, so I figure it will probably be fine with pinion preload and backlash reset. I pulled it and brought it home for $138
Note: the gov lock isn't the greatest, but for the price it's something at least to start with, and the GM diffs can all be upgraded with other options. So I'll go with it for now and see how it performs.
So, the naive aspect was I did not know that there are multiple versions of 14 bolt GM rear axles. The biggest differences are:
9.5" ring gear, semi floating axle. GM 2500 series. This one has a different sized diff case and different rear cover which can be identified by it's rounder shape. It is not quite as heavy duty as the full floaters, but should be plenty adequate for the Sprinter. It is a pretty large increase in ring and pinion size, and the axles and tubes are heavier.
10.5 ring gear, full floating axle. GM 2500 HD series identified by larger diff housing, more angular diff cover, full floating axle bearing protruding through wheel center with bolted on cap, and pinion mounted into a bearing/hub assembly that bolts into the diff housing
11.5" ring gear full floating axle GM 2500HD-3500 series has all the same attributes as the 10.5 except the pinion gear does not have the additional hub which mounts to the housing, rather having bearings mount directly into the diff housing
Some of them apparently started having ABS sensors in 2006, but back to around the beginning of the GMT800 series, the rear ABS function was based only on rear axle speed, not independent wheel speeds for each rear wheel. This was accomplished with a speed sensor at the output shaft of T case or transmission.
There is a kit for adding wheel sensors and tone rings on the 10.5 axle: https://www.artecindustries.com/abs_kit_14b But these rings do not have a number of teeth that easily multiplies/divides in order to manipulate for inputting into the Sprinter's ESP computer. The ideal would be to have a set cut with with 44 teeth.
Likewise, another aspect like with Luthj's 4wd conversion is if you use a GM rear that does have independent sensors, they are 55 tooth (vs T1N's 44 tooth so frequency needs to be corrected before signal is sent to Sprinter ESP/ABS system. This is more mathematically desirable that the kit above since 55 is divisible by the integer 11, not a repeating decimal. We both are already using an arduino based circuit to correct the front wheel speed frequencies from the 55 tooth rings, so it would be do-able to use the same circuit for rear wheels, but if 44 tooth tone rings could be used, so much the better.
Another problem looking at more recent GM axles is that somewhere around 2011 wheel bolt circle diameter went from 156mm to 180mm.
So after realizing I may have set myself up for failure with the 9.5" axle I purchased, I sought options to add sensors to play well with the Sprinter.
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