Prowrench Posted August 17, 2019 Share Posted August 17, 2019 does anyone know what year the R model went from a multi leaf spring on the steering axle to the 3 leaf spring? Quote Link to comment https://www.bigmacktrucks.com/topic/58661-r-model-multi-leaf-steer-axle/ Share on other sites More sharing options...
blackdog2 Posted August 17, 2019 Share Posted August 17, 2019 Mid 70s ? Quote Ed Link to comment https://www.bigmacktrucks.com/topic/58661-r-model-multi-leaf-steer-axle/#findComment-430268 Share on other sites More sharing options...
Prowrench Posted August 17, 2019 Author Share Posted August 17, 2019 3 hours ago, blackdog2 said: Mid 70s ? That's what I'm guessing wish i could pin down a year Quote Link to comment https://www.bigmacktrucks.com/topic/58661-r-model-multi-leaf-steer-axle/#findComment-430281 Share on other sites More sharing options...
blackdog2 Posted August 18, 2019 Share Posted August 18, 2019 They are interchangeable buy taking out spacer block but leaving the wedge . Quote Ed Link to comment https://www.bigmacktrucks.com/topic/58661-r-model-multi-leaf-steer-axle/#findComment-430337 Share on other sites More sharing options...
JoeH Posted August 18, 2019 Share Posted August 18, 2019 (edited) My 79 has 3 leaves on an 11k steer axle, just bought an '88 with 4? Leaves on a 20k steer axle, and I have a 95 with a 16 leaf 18k steer axle. The 79 is an R686st 88 is an RD690S 95 is an RD688S It's not really a year thing, it's more of a weight rating thing.... Edited August 18, 2019 by JoeH Quote Link to comment https://www.bigmacktrucks.com/topic/58661-r-model-multi-leaf-steer-axle/#findComment-430353 Share on other sites More sharing options...
JoeH Posted August 18, 2019 Share Posted August 18, 2019 (edited) And to add, I have a retired 1980 DM686SX with a 20k steer axle, I would guess 12-16 leaves but I never counted that truck. Edited August 18, 2019 by JoeH Quote Link to comment https://www.bigmacktrucks.com/topic/58661-r-model-multi-leaf-steer-axle/#findComment-430354 Share on other sites More sharing options...
Prowrench Posted August 19, 2019 Author Share Posted August 19, 2019 Well I guess I should have worded my query differently. The older R's had a multi leaf that was pinned in the front and was a slipper at the rear, at some point the R's started using a "taper leaf" which was commonly 3 leaves pinned at front and the rear of that spring pinned to a shackle and the shackle pinned to the hanger drawing is the old style on R's photo is new style What year was the change on R's? the rear spring hanger is very different and maybe the front On 8/17/2019 at 5:27 AM, blackdog2 said: Mid 70s ? That's what I'm guessing wish i could pin down a year Quote Link to comment https://www.bigmacktrucks.com/topic/58661-r-model-multi-leaf-steer-axle/#findComment-430399 Share on other sites More sharing options...
Maxidyne Posted August 19, 2019 Share Posted August 19, 2019 IIRC the taper leafs first appeared in the 70s, but most heavy trucks were still available with a conventional spring pack well into the 80s and beyond. Quote Link to comment https://www.bigmacktrucks.com/topic/58661-r-model-multi-leaf-steer-axle/#findComment-430404 Share on other sites More sharing options...
JoeH Posted August 19, 2019 Share Posted August 19, 2019 That's a more accurate phrasing of what you're trying to find out. My 79 is shackled. I have an old U model and a steel dash R Ill look at today and see how they're set up. Quote Link to comment https://www.bigmacktrucks.com/topic/58661-r-model-multi-leaf-steer-axle/#findComment-430408 Share on other sites More sharing options...
JoeH Posted August 19, 2019 Share Posted August 19, 2019 My 1980 DM is a slipper style rated at 20k, 12 leaf. Quote Link to comment https://www.bigmacktrucks.com/topic/58661-r-model-multi-leaf-steer-axle/#findComment-430412 Share on other sites More sharing options...
Prowrench Posted August 19, 2019 Author Share Posted August 19, 2019 32 minutes ago, JoeH said: My 1980 DM is a slipper style rated at 20k, 12 leaf. A DM is different than an R I'm just trying to figure out what year the change took place, I'm willing to bet it was when square fuel tanks changed to round. Quote Link to comment https://www.bigmacktrucks.com/topic/58661-r-model-multi-leaf-steer-axle/#findComment-430413 Share on other sites More sharing options...
JoeH Posted August 19, 2019 Share Posted August 19, 2019 Probably also around the time they added 3 inches to the back of the R cab too. Quote Link to comment https://www.bigmacktrucks.com/topic/58661-r-model-multi-leaf-steer-axle/#findComment-430437 Share on other sites More sharing options...
Prowrench Posted August 20, 2019 Author Share Posted August 20, 2019 10 hours ago, JoeH said: Probably also around the time they added 3 inches to the back of the R cab too. I'm thinking you are correct padded dash, new style suspension and add depth to the cab. I'm guessing the change in the suspension was due to the fact that the old multi leaf would cause your foot to bounce the throttle at 45 mph not 44 not 46 but at 45 and what a pain that was, couldn't give it more throttle unless you shifted to 5th couldn't drop r's otherwise you'd be too low Quote Link to comment https://www.bigmacktrucks.com/topic/58661-r-model-multi-leaf-steer-axle/#findComment-430474 Share on other sites More sharing options...
Maxidyne Posted August 20, 2019 Share Posted August 20, 2019 ahh, if it were only so simple... This was back in the age when the customer was always right, even if the customer demanded a Detroit engine, Fuller transmission, Rockwell axles, and about the only thing Mack was the cab and if was a conventional a subcontractor built it. Continental Baking bought 200 odd Mack Western F models with just those specs, they were almost identical to their Freightliners except for the Mack cab. One of the big oilfield service companies bought a fleet of WS models in 1980 with Detroit 6V-92Ts and heavy axles to carry high pressure pumps powered by Detroits. Looking around the new trucks at a Mack dealers lot you'd find similar looking trucks, one with the old style stack of springs and one with taperleaf. And that's just the beginning of the "kid in the candy store" options filling the thick data books... Stuff like "Hotchkiss rear suspension with taper leaf springs", air starters, and a long list of aluminum components up to and including aluminum frame rails... Those were the days! Quote Link to comment https://www.bigmacktrucks.com/topic/58661-r-model-multi-leaf-steer-axle/#findComment-430475 Share on other sites More sharing options...
JoeH Posted August 20, 2019 Share Posted August 20, 2019 Not sure what you mean by bounce the throttle; my 79 gets a hop in the chassis around 45 mph or so, it has the shackle style steering springs. Gotta plant your heel. Quote Link to comment https://www.bigmacktrucks.com/topic/58661-r-model-multi-leaf-steer-axle/#findComment-430478 Share on other sites More sharing options...
Prowrench Posted August 20, 2019 Author Share Posted August 20, 2019 6 hours ago, JoeH said: Not sure what you mean by bounce the throttle; my 79 gets a hop in the chassis around 45 mph or so, it has the shackle style steering springs. Gotta plant your heel. that's exactly what I mean but I never experienced that on the newer springs Quote Link to comment https://www.bigmacktrucks.com/topic/58661-r-model-multi-leaf-steer-axle/#findComment-430491 Share on other sites More sharing options...
JoeH Posted August 20, 2019 Share Posted August 20, 2019 My 79 does it, we figure it's just a driveline balance thing or just how the truck is loaded. Started life with a 5tg wheel, but we have a concrete mixer on it with most of the weight sitting on the Camelback. On a full load I probably have 12.5k on the steer (rated at 11k) and 40k on the Camelback (rated at 38k). My guess if it's not a driveline balance issue is just soft springs on the front with a top heavy load. Come to think of it, there's a 100 yard section of road near me that would make my 95 rd688s triaxle do it at like 42mph itd get that same hop going. If I went through slower or faster it wouldn't do it. But they repaved the road last year so it doesn't do it any more. Quote Link to comment https://www.bigmacktrucks.com/topic/58661-r-model-multi-leaf-steer-axle/#findComment-430493 Share on other sites More sharing options...
Dirtymilkman Posted August 31, 2019 Share Posted August 31, 2019 It's all how you order the truck. You can still spec multi leaf front springs. I have had less maintenance with them. It seems the taper leaf eat bushings more often. Multi leafs are stiffer ride though. Quote Link to comment https://www.bigmacktrucks.com/topic/58661-r-model-multi-leaf-steer-axle/#findComment-431201 Share on other sites More sharing options...
Prowrench Posted September 1, 2019 Author Share Posted September 1, 2019 10 hours ago, Dirtymilkman said: It's all how you order the truck. You can still spec multi leaf front springs. I have had less maintenance with them. It seems the taper leaf eat bushings more often. Multi leafs are stiffer ride though. they certainly are, the multi leaf were sandwiched in a slipper pad at the rear which was more forgiving to extreme travel of the spring Quote Link to comment https://www.bigmacktrucks.com/topic/58661-r-model-multi-leaf-steer-axle/#findComment-431237 Share on other sites More sharing options...
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