Ray Cecil Posted October 4 Share Posted October 4 .....AAAAAAANNNNNNNDDDDDDDD.........GO! I keep waiting for my C6 to give up the ghost. Ive seriously just considered rebuilding it once it does, but it would be the perfect time to swap to a manual when it does. Ive never liked the way it shifts. I have to press hard on the accelerator to get a positive 1-2 shift. 2-3 works fine but that 1-2 shift is horrible. Maybe I have something out of adjustment. I manually shift it most of the time anyway. Its a 6 speed semi-auto with that Gearvendor unit. I like splitting gears in my 4 speed +2 rear axle International. I'd kind of like the same feel in the F250. I don't haul a lot. The truck is still a candidate for a Diesel Electric Hybrid if for some reason I decide to not do the conversion on the International. The ZF5 I am a member of many FB groups, Im always watching and waiting for something to pop up locally, but every other post is about an aluminum case getting cracked and needing to be welded. Ive never heard of a cracked T19. So I am thinking the T19+a gear vendors sort of equates to a 6 Speed....like the ZF6....obviously not perfect oranges to oranges there, but you get the point. Link to comment Share on other sites More sharing options...
Gary Lewis Posted October 4 Share Posted October 4 I don't know what the GV overdrive ratio is, but I'd go to our page at Documenation/Driveline/Calculators and put that ratio in the Transfer Case Low Range Gear Ratio - Other cell and then go compare your overall gear ratios of the ZF5 vs the T19. Put in your tire size and speed and see what the engine would be turning in each gear, with and without the GV. As for comparing them, I think the ZF is delicate. Mine had all sorts of problems when I got it and I had it completely rebuilt and still the 3rd synchro is iffy. But the T19 I had shifted fine w/o being rebuilt. However its 3rd gear was too low and you ran out of revs before you got to the speed you wanted. Maybe that wouldn't be an issue with the GV, but I'd go check it out. 1 Link to comment Share on other sites More sharing options...
Ray Cecil Posted October 4 Author Share Posted October 4 Not sure if your calculator is correct. Or maybe I am not understanding how to input or read the chart. I have a c6, 4.10, 265x75-16, 31.6" Diameter Tire, BW1356 and the Gearvendor is .78:1. I cruise 65mph at about 2650-2700rpm. Your chart reads I should be at 56mph?? What am I doing wrong here? Link to comment Share on other sites More sharing options...
Gary Lewis Posted October 4 Share Posted October 4 You are missing the statement in the Add-on OD row that says "The overall gear ratios will be shown in the 3rd green box below." In other words, the OD ratio is not taken into account in the #'s you are looking at. But, that seems like a poor design. You'd really like to know what speeds and RPMs you'd get in each gear, not just the gear ratio. So what we really need is another box that uses those ratios to calculate speeds and RPMs. Right? 1 Link to comment Share on other sites More sharing options...
Gary Lewis Posted October 5 Share Posted October 5 @Ray Cecil - I got started on adding the OD calcs in for RPM. See what you think, please. 1 Link to comment Share on other sites More sharing options...
Gary Lewis Posted October 5 Share Posted October 5 @Ray Cecil - See what you think. I believe it is correct but please check it out. And I wonder if I should put the With Add-On OD bit on a separate tab? Thoughts? I could do it for a test. Link to comment Share on other sites More sharing options...
Littlebeefy Posted October 5 Share Posted October 5 I am running a s5-47 behind a 460 with an RV cam pushing around 550 ft-lbs gross. The ZF5 seems to be just fine with it. I’m not pulling anything, tho. I love the granny gear and am still cruising happily at 75mph in 5th running 2200 RPM. Link to comment Share on other sites More sharing options...
Gary Lewis Posted October 5 Share Posted October 5 I have the S42 with a 460 capable of 500 lb-ft and I've used it many times pulling a trailer with a vehicle on it and it hasn't broken. So maybe I should have said the synchros are delicate as that's the only problem I've had since the rebuild. Link to comment Share on other sites More sharing options...
Littlebeefy Posted October 5 Share Posted October 5 Also, I have an iron NP205 hanging off the tailhousing (supported with a frame mounted bracket like the 79). That thing weighs about the same as the ZF5 does. Again, no problems. That aluminum seems to be holding up just fine. 1 Link to comment Share on other sites More sharing options...
Ray Cecil Posted October 6 Author Share Posted October 6 19 hours ago, Gary Lewis said: @Ray Cecil - See what you think. I believe it is correct but please check it out. And I wonder if I should put the With Add-On OD bit on a separate tab? Thoughts? I could do it for a test. This is much closer to what I am seeing on my tach. Although, this calculation seems to be off from what I am actually seeing. Ive paid attension to the rpms since this last post. On flat ground, cruising, I am 2650rpms at 65mph. So, either my torque converter slips more than 250rpms, or my tach is off, or some other driveline variable is a little off. Link to comment Share on other sites More sharing options...
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