Guest zfan Posted March 21, 2006 Share Posted March 21, 2006 Does anyone know where I can find an article or write up regarding horsepower losses with each transmission listed above. I would love to know if a TH350 really gains you anymore power vs say a 700R4 or even a P. Glide. I always hear that a 700R4 is a hp hog and that TH350's and powerglides are so much more effecient. I wonder if someone has taken in a step further and dyno'd said trannies for a true comparison. Mike Quote Link to comment Share on other sites More sharing options...
dr_hunt Posted March 22, 2006 Share Posted March 22, 2006 I can guarantee you that the PG is the most efficient of any automatic you listed. Then comes the 350 and then the 700 r4. It's simple, rotating mass and parasitic losses attributed to OD trannies. The PG has the minimum rotating mass and it's direct through in high. TH350 has an extra clutch pack to turn and more mass. 700r4 has the extra clutch pack and parasitic losses with the OD gearing. Quote Link to comment Share on other sites More sharing options...
76brkracer Posted March 22, 2006 Share Posted March 22, 2006 very well put dr. Quote Link to comment Share on other sites More sharing options...
Guest tony78_280z Posted March 22, 2006 Share Posted March 22, 2006 Interesting,. Any data on that? I'd like to know an amount or % of parasitic HP loss. Quote Link to comment Share on other sites More sharing options...
dr_hunt Posted March 22, 2006 Share Posted March 22, 2006 If my memory serves me correctly the PG takes at most 80 to 100HP, depending on how it's built and what pump you use, the th350 is about 125HP. I don't know about the 700R4 but the th400 is bout 135hp. The PG can be built with some lightweight parts for less rotating mass, looser reverse clutch clearance for less friction. I'm sure you could do the same with some of the other trans but the PG is king. Quote Link to comment Share on other sites More sharing options...
Guest tony78_280z Posted March 23, 2006 Share Posted March 23, 2006 Wow!! That much? So a 300hp motor with a TH400 is putting 265, to the drive shaft, and less than that to the wheels? A 700r4 is worse?! I hadn't thought it was that much. I'm gonna need more horse power!! How do the manuals transmissions fair? Quote Link to comment Share on other sites More sharing options...
dr_hunt Posted March 23, 2006 Share Posted March 23, 2006 Well, that depends on what gear the trans is in, those numbers are for first gear I believe. Manual transmission take less power usually about 15% and auto's are around 20%. Over drives soak up alot of HP in OD due to parasitic losses and rotating mass cause it's rotating the other clutch packs. So in high gear with a 400 HP engine your only delivering 320 to the rear end. Loose another percentage in the rear end and your probably barely getting 300 at the wheels. You get alot less in the lower gears of an automatic, but you get torque multiplication which is what moves the vehicle. Quote Link to comment Share on other sites More sharing options...
Guest tony78_280z Posted March 23, 2006 Share Posted March 23, 2006 When there is a parasitic HP loss, there is also a parasitic MPG loss. Well, here is a theory. If there is 100hp loss for TH350, and 135hp loss for a Th700r4 that is a 1.35 increase in parasitic loss between the two. If you take this common data... Turbo 350 1st: 2.52 2nd: 1.52 3rd:1 4th:N/A Turbo 400 1st: 2.48 2nd: 1.48 3rd:1 4th:N/A 700R4 1st: 3.06 2nd: 1.63 3rd:1 4th:0.7 the 700r4 has a 1.3 increase (MPG wise) of gear ratio over the Th350 in high gear. But if you add the 1.35 parasitic loss you get worse MPG TH350. maybe I'm missing something, but if my math comes out right a 700r4 with the overdrive shouldn't produce as good MPG as a 1:0.7 would lead you to believe (I'm starting to regret my choice of transmission) If the TH350 has less than 100hp in parasitic losses (as you said 80-100) then my math is obviously off a bit, but that would explain why some people say they saw little or no MPG increase when switching to the 700r4 from 350, and some said they saw just a few miles increase in MPG. What say you? What can one do to relive these parasitic losses in the transmission? Quote Link to comment Share on other sites More sharing options...
dr_hunt Posted March 23, 2006 Share Posted March 23, 2006 When you get into OD you loose TQ multiplication, your turning more gears and bearings, can't do anything about it. Clutch friction is minimized by increasing clutch pack clearance, but only to a certain extent. Lightened rotating components also help with acceleration. MPG increase is often achieved when you can reduce losses which would mean go to a direct drive manual transmission rather than an auto, especially an OD auto. You can't add gears, bearings and a cluth pack and have an increase in mileage all other thing being equal. The only advantage to an OD would be the reduction in engine parasitic losses due to lower operating rpm which is offset by the increased transmission parasitic losses. But why would you do that when you could get a OD manual box and have lower transmission parasitic losses? I think the TH400 is the real pig with 23% loss in high gear. If it's mpg's your looking for then a manual box is by far the way to go. Quote Link to comment Share on other sites More sharing options...
Guest zfan Posted March 23, 2006 Share Posted March 23, 2006 My sbc 385 stroker is an 11 to 1 motor and is mated to a 700r4 with a 9.5 converter/3500 stall. It puts down approx. 367 hp and 420 Tq to the wheels. So yes that 700r4 is a hp robbing pig! Mike Quote Link to comment Share on other sites More sharing options...
dr_hunt Posted March 23, 2006 Share Posted March 23, 2006 One of these days when on the dyno, somebody try to get them to do a pull in first gear just so you get a feel for what HP you really loose and then you'll know why heat is what kills transmissions. Pulling heavy loads in lower gears creates alot of heat in the trans. Quote Link to comment Share on other sites More sharing options...
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