Landracing Forum
Bonneville Salt Flats Discussion => Bonneville General Chat => Topic started by: metermatch on June 24, 2020, 05:40:41 PM
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I was wondering if anyone knew if/where I could find a pinion coupler for a GM 7.5 rear end? Car is a RMR with XO engine, currently trans has a coupler direct to a Ford 9" rear. I was thinking I could solve a number of problems at once by going to a GM 7.5 rear to save some friction loss, get taller gears than available for a Ford 9" for my low rpm motor, and also remove about 8" in width from the rear end at the same time.
Anybody have any other ideas on how to do this, short of a 3" driveshaft length u joint to u joint if it were to even exist?
What is the bare minimum driveshaft length possible, if I were to move the rear end back a few inches and use a standard yoke on the 7.5 rear?
Thanks,
Jeff
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I think B&J made some I had 2 made but I do not want to sell mine. Sid Kiwi belly tank knows about them. welcome to the GM 7.5 admariation society
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If you're not running suspension the Greek Couplers will work. I had Mike at B&J custom build some for me so he can make them to order for your 7.5 10 bolt. The part number is B&J-SID.
If you want to run a U-joint, there is an early 2000's Sonoma that has a flat flange. I have one here that's surplus to my requirements if you want it.
Sid.
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Thanks for the quick responses. I will call B&J tomorrow.
While on the subject, is there a difference in efficiency between a coupler and a driveshaft? Any other advantages/ disadvantages between the two for a solid, no suspension type installation, other than the obvious car configuration space limitations? Is a coupler hard on trans or differential bearings/seals?
Are couplers lubed? I just did major maintenance on a Honda Goldwing GL1500 I just bought, and the shaft drive parts have splines. Honda requires a special high moly content paste (65%+) applied to the splines, apparently this stuff really sticks to the splines. Is something similar needed for a spline coupler installation?
Thanks,
Jeff
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I spoke with Mike at B&J transmission today. He thinks he has a GM 7.5 pinion coupler somewhere or will make one for me. Probably be 2-4 weeks, as he can fit it in, cost probably around $125. If anyone else would like one, call him now. He seems like a good guy to work with.
Jeff
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IF you work at it you can fit the coupler where you can rattle it when you are stationary-- there then should hardly be any difference in the parasitic loss.
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I have a couple of 7 1/2 10 bolt 2.14 ring and pinions of anybody needs them .
joyseydevil@comcast.net
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Thanks for the quick responses. I will call B&J tomorrow.
While on the subject, is there a difference in efficiency between a coupler and a driveshaft? Any other advantages/ disadvantages between the two for a solid, no suspension type installation, other than the obvious car configuration space limitations? Is a coupler hard on trans or differential bearings/seals?
Are couplers lubed? I just did major maintenance on a Honda Goldwing GL1500 I just bought, and the shaft drive parts have splines. Honda requires a special high moly content paste (65%+) applied to the splines, apparently this stuff really sticks to the splines. Is something similar needed for a spline coupler installation?
Thanks,
Jeff
I presume you're talking about the male/female connection of the Greek Couplers. The alignment of trans & pinion need to be perfect so there is no binding obviously. Most people run them dry without any problem but if you're going to grease it that might be a salt trap.
Mike is cool, he & his whole family are Bonneville racers.
Sid.
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Good idea about using NO grease because it will be a salt trap. I will work extra hard to just get the alignment done right the first time.
Are there any things I should look for or which vehicles to get an axle from in the junkyard? Any particular years? I am going to have to narrow it to about 50" any rear I get, so stock width is not a factor
Which vehicles might have a posi, and should I run it? I don't think spools are available. Is it worth getting a 28 spline over a 26 spline? I assume aftermarket axles are a good idea?
Are those heavy cast aluminum covers with the two screws that push against the main caps worth getting?
Thanks,
Jeff
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Regarding the posi ? it's like the 2-party system. Take your chances on getting it right in my opinion.
I put one in to make a record-qualifying run. Made it to the three. Got a spectacular view of the whole lakebed.
Changed to the one-leg ? went record-record.
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I have heard similar accounts, but why? Is it because with a posi, if one side loses traction, the other side will keep pushing to the side with no traction, causing a spin? If so, then what are the drawbacks with an open rear?
I have heard to use a spool, but if an axle breaks, or one side loses traction, is it the same result as a posi?
Is the open rear safer because if a tire breaks loose, you just go up in smoke until you back off the throttle, and regain traction and then accelerate?
Jeff
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Beats me.
Only made one run with a posi. Notice how the signs are reading backwards. I don't know why this happened. Set the record in two runs the next day at 210. Your results may vary.
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Ok Jeff, here's the best info I can give you.
The strongest center housing is Gen 3 & later Camaro due to being a Nodular Iron housing with extra meat for the torque arm mount. Most of the other housings are cast iron.
The weak link in most carriers is the cross pin for the spider gears so if you go to a Torsen carrier it eliminates that problem because it is a spiral gear unit that spreads the drive load over a large gear area. There are a few different types of LSD's for them from clutches to govlocks & they all come on differently but the Torsen is always on & variable & won't surprise you. With an open center you are back to the weak cross pin again & you still have it even with a mini spool.
The 2 series is for the "high ratio" gears from 3.08 up to 2.14. (a lot of people seen to get that backwards) The 3 series is for the lower ratios from 3.23 all the way down to something like 4.30.
Do 28 spline, that way you can change to a 9" Ford style hub & easily get custom 28 spline 9" axles for your particular length.
The cast aluminum rear cover/girdle has supports that screw down onto the bearing caps as support, don't leave home without one.
The axle tubes are never installed straight in a 7-1/2" housing so use a center bar through it when you weld the ends on.
Sid.
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All good ideas. Thanks.
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I have made a few driveshafts using only a double cardon cv h-bar without any of the other cv parts. The typical C-L to C-L length is 3.25? these are available in 1310, 1330 and 1350. They will allow for some misalignment too.
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Do have a picture of this type of driveshaft/joint? I'm having trouble picturing it. Do you make these? Ballpark figures, how much?
I don't have any actual problem with using a coupler - I would prefer to use a common size u-joint and driveshaft setup so I can run different engines in thee car. The current engine, a 1950 Buick 320 straight 8 is so long that it almost requires the use of a coupler, but with the smaller GM 7.5 rear, (currently Ford 9") and relocating the rear end a few inches aft, I could probably find 3-4 more inches. I would rather install a u joint flange on the rear instead of a coupler so I don't have to change it when switching engines, Get it set up once and forget it.
Jeff
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This is what he's talking about. They are typically used on off-road 4x4's where there is going to be extreme shaft angles & low rpm. Universal joints consume power because their speed is not constant & the more angle there is the more power they suck up.
Sid.
https://www.google.com/search?q=double+cardan+shaft+alignment&rlz=1C1CHBD_enUS788US788&sxsrf=ALeKk00Tr9es1JTdycO0lpRc_IwV4HsTBQ:1594264219044&tbm=isch&source=iu&ictx=1&fir=e7Hpe8TGGblOtM%252C0ieOoKCd6jEXKM%252C_&vet=1&usg=AI4_-kSmoiENCckFInbX1Ww9zPZaw0_QoQ&sa=X&ved=2ahUKEwil4NCDmb_qAhWDs54KHeUcCX0Q9QEwBXoECAYQIw&biw=1024&bih=657
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M vans have difffernt axle tubes you can get Toresend centers off ebay that were in early-mid 80's firebirds and camaros they work great and have 28 splines---the axle tubes in the 7.5s are not paralell but you can adjust when you weld ford 9" ends in them to get rid of the c clips if you want a wider track use a camaro PU and Ms have shorter heaver axle tubes I think all of this is correct
I have run 2 u-joints 3 u-joints and a coupler---I tried to center the trans output and the rear pinion every time with the car wet and read for a run---a lot harder than one would guess
Sids memory and knowledge are better than mine
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https://encrypted-tbn0.gstatic.com/images?q=tbn%3AANd9GcRV6TIcZvO8Ke5N9EY2nYgjfaUadYcN_Dc4kg&usqp=CAU