JoeH Posted December 11, 2023 Share Posted December 11, 2023 In my hunt for off-road traction for my concrete trucks, I've come across some interesting info. Older CRD92/93 rear carriers apparently had a limited slip style differential option, and those carriers would be CRD921/CRD931. The newer CRD1501/1511 version uses an air cylinder with fork to slide a locking clutch through the differential to lock it. Does the CRD921/931 do similar? In the CRD92/93 service manual it seems to imply that it's an automatic torque biasing cage with wedges much like the automatic inter-axle power divider. Does anyone on here know anything about these rears? I suspect trying to aquire a pair of these differentials would be like trying to bottle unicorn farts. Quote Link to comment https://www.bigmacktrucks.com/topic/73638-crd921crd931-inter-wheel-lock-differential/ Share on other sites More sharing options...
JoeH Posted December 11, 2023 Author Share Posted December 11, 2023 The service manual on the 150/151 carriers shows an air cylinder with a wire pigtail for alarm sound in some of the pictures for the CRD1501/1511 inter-wheel locking differentials, but the CRD92/93 book is largely lacking on showing any possible variations in the carrier housings to accommodate any sort of air actuated differential lock. Quote Link to comment https://www.bigmacktrucks.com/topic/73638-crd921crd931-inter-wheel-lock-differential/#findComment-543265 Share on other sites More sharing options...
Joey Mack Posted December 11, 2023 Share Posted December 11, 2023 Ok.. the 92/93 series came with auto power dividers as well as air operated locking power dividers.. Quote Link to comment https://www.bigmacktrucks.com/topic/73638-crd921crd931-inter-wheel-lock-differential/#findComment-543267 Share on other sites More sharing options...
Mark T Posted December 11, 2023 Share Posted December 11, 2023 Never saw a 92/93 with the set up, but 200s they had ones like you described. Instead of spider and side gears, they had a cam and wedges quite similar to the interaxle power divider. There was no lockout on them like on newer Mack or Meritor/ Spicer lockers . They cost a small fortune to repair. Quote Link to comment https://www.bigmacktrucks.com/topic/73638-crd921crd931-inter-wheel-lock-differential/#findComment-543271 Share on other sites More sharing options...
JoeH Posted December 11, 2023 Author Share Posted December 11, 2023 I've seen 112/113, 150/151, 200's mentioned, what are the differences? The 92/93 book mentions the 112/113's. Are they weight ratings? Generations? Housing differences to accommodate taller ratios? Quote Link to comment https://www.bigmacktrucks.com/topic/73638-crd921crd931-inter-wheel-lock-differential/#findComment-543277 Share on other sites More sharing options...
JoeH Posted December 11, 2023 Author Share Posted December 11, 2023 What's a common application that would have been buying the inter-wheel locks? Fire trucks? Municipal Plow trucks? Quote Link to comment https://www.bigmacktrucks.com/topic/73638-crd921crd931-inter-wheel-lock-differential/#findComment-543278 Share on other sites More sharing options...
fjh Posted December 11, 2023 Share Posted December 11, 2023 4 minutes ago, JoeH said: What's a common application that would have been buying the inter-wheel locks? Fire trucks? Municipal Plow trucks? We sold dozens of these back in the late eighties and 90's ! ive seen them in log trucks fire trucks dump trucks never in mixers however...... ! also I can't tell you how many mixers I have seen specked without the interaxle lock! Don"t have a clue why anyone would spec a diff for any vocational truck with out Both interaxle and diff lock on both axles! And yes the mack limited slip was the wedge and cam set up inside the diff cage! It worked ok on off road applications but as a single axle or tandem on rd application tended to bang and pop going round corners causeing one to think his diff was failing! In my opinion there is no replacement for having a fully lockable diff for any application! They blew it! The new redesigned Mack carrier they were able to ad the diff lock however they also redesigned how the crown gear and preload was applied to the top gear set! They changed the retaining bolts from 3 half inch fine bolts to One 3/4 inch yoke bolt similar to the trans yoke bolt! I don't know if they are still having issues with this coming loose cause I have retired from this for a year or two however I repaired several of these due to this ill thought out redesign ! The old story if it aint broke don't fix it! Quote Link to comment https://www.bigmacktrucks.com/topic/73638-crd921crd931-inter-wheel-lock-differential/#findComment-543280 Share on other sites More sharing options...
Mark T Posted December 11, 2023 Share Posted December 11, 2023 8 hours ago, JoeH said: I've seen 112/113, 150/151, 200's mentioned, what are the differences? The 92/93 book mentions the 112/113's. Are they weight ratings? Generations? Housing differences to accommodate taller ratios? Simply put, the higher the number the heavier the carrier was. Like a basic tractor would pretty much have 92/93s a bigger spec truck with say.. 58s would have 112/113s (bigger and accommodated bigger axles) the 200s were sorta in between and if I remember at the time anything with over a 400 (?) dictated getting 200s I bought a cutoff out of Canada once. It had 200 series carriers in 461s that had the differential lockers. I have no idea what they were in other than as best I could guess they came out off an RW or CL. Between the different series' the ratios were usually off from one another by a few hundreths of a turn or so. Quote Link to comment https://www.bigmacktrucks.com/topic/73638-crd921crd931-inter-wheel-lock-differential/#findComment-543301 Share on other sites More sharing options...
Joey Mack Posted December 11, 2023 Share Posted December 11, 2023 12 hours ago, Mark T said: Never saw a 92/93 with the set up, but 200s they had ones like you described. Instead of spider and side gears, they had a cam and wedges quite similar to the interaxle power divider. There was no lockout on them like on newer Mack or Meritor/ Spicer lockers . They cost a small fortune to repair. Seem's to me,, I should know better.. I'm surprised I got this one wrong.. I guess the 'rust' is getting thicker...... i dont recall re-building anything other than 92/92 and 200 series carriers.. JoeH ?? what rear end book are you using? I have a large set, and want to see what yours looks like.. Jojo Quote Link to comment https://www.bigmacktrucks.com/topic/73638-crd921crd931-inter-wheel-lock-differential/#findComment-543305 Share on other sites More sharing options...
JoeH Posted December 12, 2023 Author Share Posted December 12, 2023 Pull out any 92/93 book and look up inter-wheel in the table of contents. Its there. I believe mines dated 1986. Quote Link to comment https://www.bigmacktrucks.com/topic/73638-crd921crd931-inter-wheel-lock-differential/#findComment-543308 Share on other sites More sharing options...
JoeH Posted December 12, 2023 Author Share Posted December 12, 2023 My dad bought a giant 3 binder set in the mid 80's when he bought our first Mack, the 1979 he's still driving. Quote Link to comment https://www.bigmacktrucks.com/topic/73638-crd921crd931-inter-wheel-lock-differential/#findComment-543309 Share on other sites More sharing options...
Joey Mack Posted December 12, 2023 Share Posted December 12, 2023 ok.. I got my books at school in 2002, and again in 2018.. I guess I could take a look, just because.. BTW,, I like the new to you MR.. Jojo Quote Link to comment https://www.bigmacktrucks.com/topic/73638-crd921crd931-inter-wheel-lock-differential/#findComment-543310 Share on other sites More sharing options...
JoeH Posted December 12, 2023 Author Share Posted December 12, 2023 Thanks, hoping we don't set something on fire trying to get it to start lol! It has a switch in the cab to shut power off, red wires labelled RD-A(B through G)-19.0. I'm guessing they're general component power for the power distribution. Wires A and AB are down by the starter going to a Klixon circuit breaker that looks sketchy. Quote Link to comment https://www.bigmacktrucks.com/topic/73638-crd921crd931-inter-wheel-lock-differential/#findComment-543313 Share on other sites More sharing options...
Mark T Posted December 12, 2023 Share Posted December 12, 2023 15 hours ago, Joey Mack said: Seem's to me,, I should know better.. I'm surprised I got this one wrong.. I guess the 'rust' is getting thicker...... i dont recall re-building anything other than 92/92 and 200 series carriers.. JoeH ?? what rear end book are you using? I have a large set, and want to see what yours looks like.. Jojo Joey...... you feel surprised ??? You should pull one out expecting to be replacing your basic garden variety rear rear ( @ $1800.00 ) then discover it's one of those and just like that POOF $4500.00. This was back in 1998 mind you 🤣. 1 Quote Link to comment https://www.bigmacktrucks.com/topic/73638-crd921crd931-inter-wheel-lock-differential/#findComment-543344 Share on other sites More sharing options...
kt_Engineer Posted December 14, 2023 Share Posted December 14, 2023 On 12/10/2023 at 11:34 PM, JoeH said: In my hunt for off-road traction for my concrete trucks, I've come across some interesting info. Older CRD92/93 rear carriers apparently had a limited slip style differential option, and those carriers would be CRD921/CRD931. The newer CRD1501/1511 version uses an air cylinder with fork to slide a locking clutch through the differential to lock it. Does the CRD921/931 do similar? In the CRD92/93 service manual it seems to imply that it's an automatic torque biasing cage with wedges much like the automatic inter-axle power divider. Does anyone on here know anything about these rears? I suspect trying to aquire a pair of these differentials would be like trying to bottle unicorn farts. CRD150/151 was introduced in 2009 to replace CRD92/93. This is the first Mack axle series with Differential Lock option (i.e fork/clutch to lock left and right wheels). CRD921/931 is the Interwheel power divider/Limited Slip Differential (identical to Inter-axle differential with peanuts and cam differential) between wheels. CRD92/93 doesn't have differential Lock. CRD150/151 is also offered with Limited Slip differential option and referred to with CRD1501/1511 designation. Interwheel Power Divider differential does automatic torque biasing with 3:1 torque sent to non-slipping wheel but if other wheel is one ice with zero traction then you are going nowhere. With diff lock you should be able to move even if one wheel is on ice. Diff Lock is extremely inexpensive compared to IWPD (Inter Wheel power Divider) version 1 Quote Link to comment https://www.bigmacktrucks.com/topic/73638-crd921crd931-inter-wheel-lock-differential/#findComment-543467 Share on other sites More sharing options...
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