Th400 highway rpm So your combination in first gear would act the same as a TH400 with a 4. Is it worth it for that rpm drop (450 @ 60 mph - 550 @ 70 mph) . Have calculated that the 3. 73 gears, as I mentioned, make a decent compromise between highway and city driving if you can take the RPM on the highway. 700r4. I might do a hollow input shaft and run a lockup which should couPled with overdrive put the highway rpms ~1700 or less Sep 3, 2004 · I've never had a big block before and I'm looking for favorable rpm's this motor would like to see for occasional highway drives of 1-2 hours. The braking stall is somewhere in the 1,500 to 1,800 RPM range. 11 = 3023 RPM 3500 x 3. I have a TH400. 31's and a 28" tire. The TH400 with 3. 90 gears and the 200R4 with 3. 1). 06 first gear. TH400/3. 73/3. 08s w/ a PG and cruises OK at 70 mph (~3000-3200 rpm or so on the tach). That is why I recommend the 3. This will be matched up to my SBC 400CI/460HP/470TQ with Holley EFI. Oct 19, 2016 · C3 Tech/Performance - Gear Vendors Underdrive/Overdrive - Like many of us on this forum, I am interested in reducing my highway driving rpm's by replacing my TH400 for an overdrive automatic transmission or by replacing my TH400 for a TKO or other 5 speed manual. Apr 4, 2019 · C3 Tech/Performance - TH400 with 2. My car has 3. The car launches like a rocket , pulls through every rpm and gear and is a ***** cat when driving around town. 08. 11 = 2912 RPM Mar 5, 2023 · Those RPM's are not really hard on the engine, just the fuel mileage! I have both a 1978 C20 Camper Special with 4. 7K views 5 replies 6 participants last post by Jp outlaw Feb 25, 2010 Nov 12, 2013 · 3. 08s and 1:1 would be at 2258 rpm at 60 mph and the more likely highway cruising speed of 70 mph would give me 2587 rpm's with my 27. For the record, I had 3. 00 x 336. 3. 42. I don’t have the pro codes in this truck, but according to vin decode, 350/th400, the gears are 4. 10= 10. 55, depending on which rear end you have. TH400 alone would be an HD upgrade without a reduction in highway rpm. 2. 10 gears . [ (Axle Ratio x Vehicle Speed x Transmission Ratio x 336. You don't need a low gear with the 700R4 to have fun because of the very low first gear. This will give you a lower RPM on the highway while you still have the TH400, and will still be lots of fun with the 700R4. 75 low gear set - I'm considering a TCI/ TH400 with a 2. 48 to coupled to my 3. May 24, 2016 · I'm considering swapping the TH400 for a 700R4 to drop the highway rpm's down at cruising speed. (3,000 rpm = 75 mph) When does your cam start making power? If it's around 2,500 rpm then with 3. 73 your highway cruise RPM will be around 3000. Apr 4, 2002 · The TH-400 is just about bullet-proof, especially if you get it rebuilt by someone who knows what they're doing. 73. 73 / 4. I played around with one calculator using a 26" tall tire and first gear ratio's only. 31's to 3. If you want lower RPM's at highway speed go with a 700R4 (or a 4L80E, if you have deep pockets). My use might look like the follow: 65% Performance 35% Highway Cruiser Current Set-up: Motor: 396/325 Trans: Turbo 400 Gears: 3. 3300 rpm @ 80 is a little high imo. . I personally didn't like the highway rpms's were too much, but they werent THAT bad. The final gearing in the 400 and 350 is 1:1. 08 rear gear to harness a bit more power at take off. The rpm’s are really high, even at low highway speeds. Highway rpm in some vehicles dropped by as much as 30 percent thanks to the 700R4. Speed ?'s - Does anyone have any charts or input on the 3rd gear speeds in a TH400 with 1. 73 x 65 x 1. 54 is already a great all around combo, but with a 327, probably lacks in the low end punch - so, anyway, depending on your answer to question 1, can probably help a little more once we know your priorities. Sep 9, 2006 · drop a 700 r-4 and the gears,,,the 373 rear gears will be like a mid 4 series gear,,,because of the lower first gearin the 700 trans and you'll drop down to mid 2000 while cruising at 80,and your gas milage is gonna go way up,,,,mine was a little over 2 grand to build,,install,by my cousins shop(the 700 r-4) then there will be goodies you'll have to get from boetie like the indent shift plate Nov 8, 2013 · Any RPM x new differential gearing / existing Differential gearing = effective RPM I will choose 3500 RPM and 3. I prefer a proper th400 to a 4l80e. Mar 27, 2020 · If we divide that by the first gear ratio of a TH400 automatic transmission (which is 2. 06:1 1st. 08 rear end gears, and the 700R4, what rpm's are you turning at 70-75 mph? I've read prior threads about the pros Sep 4, 2015 · what is your highway speeds????? 3000 rpm at 55 is different then 3000 at 75. Mileage won't be great, so that alone would maybe be a push toward 3. If you are running the 3. 56 and the best thing I can say about it is that it makes a good low rpm cruiser, even with 245/60s. with a decent, not over cammed 383 you could run a TH400 and 3. 13) / 31 ] = [ 2628 ] Nov 22, 2016 · When I am cruising down the highway about about 71mph, the engine RPM is right at 3,000. With my 28. From what you posted, the peak torque is at 3700 RPM, so that would be a reasonable choice - just below peak torque at close to 70 MPH. This calculation is used to match oversize tires with new ring and pinion gears to obtain the desired engine RPM at highway speed. 42, or 3. 31 gears at 60 mph = about 2,250 rpm. Apr 21, 2003 · stock 235/85/16 tire size range would get you these rpm's @70mph with a th400 and 4. Your best chance is swapping to a 700r4, or 4l60e, or 4l80e. 10's & TH400 - both get around 10-10. Jun 4, 2016 · C5 General - TH400 RPM vs. 60:1. 3500 x 3. Even if one of those hits 20mpgs your truck is heavier and has heavier running gear. Oct 17, 2021 · With just the addition of an OverDrive, you can shave ~1,200 RPM off your highway RPM without sacrificing off-the-line performance. Oct 5, 2010 · Anyone have any idea how much a typical STOCK PG/TH350/TH400 converter slips at highway speeds? I am converting my car from an auto to a 4-spd over the winter. 1968 Firebird 400, 068 cam, TH400 & 13" Continental There isn't much that will help a th400 at highway speeds. 75 low gear set instead of a typical TH400 with a 2. Since the current cruise rpm is acceptable (to me), I am wondering how much I am losing to converter May 18, 2019 · If I set my idle at 1,200 RPM just dropping the car into gear knocks it down to 800 RPM. 13) / Tire Diameter ] = [ (3. Nov 27, 2008 · The mpg gain is nice, but my main interest was in getting the engine down to reasonable rpms in highway driving. Just talking about highway rpm's and highway cruising. com. Mar 26, 2017 · Considering going with 3:08 rear gears. Feb 23, 2010 · TH400 max rpms Jump to Latest 7. 546:1 the 700r4 will get the weight moving faster then the th400. 00 diff and 30" tall tires. Mar 30, 2020 · Bringing this thread back to life. 10's and TH400 and a 1979 C35 Dooley Camper Special with 4. They make a kit for the Vette. 31 ( for sale by the way ) Would be a great marriage to it . the th400 has a 2. 5 inch tires. 55 / 4. 42 vs 4. going from a th400 to a 700r4 is worlds apart. Tuned properly you might get up towards 16MPG. 31 gears, the engine will buck along due to cam overlap under 2,500 rpm. 31 for street/highway use and then I would run a 28" tall tire like a 275/60-15. Aug 25, 2007 · If you do no highway, and do some spirited driving, I say go 3. 48:1 1st gear. 78 gear set instead, you'll still be a few hundred RPMs higher than the 3. Let’s use that as a basis for comparison. On the other hand, I wouldn't consider anything steeper than a 3. I think 396's need all the gear they can get personally. I also have the 700R4 with a 3. Jan 26, 2010 · Also with a th400 you don't have to expand the tunnel like you do with th 4l80e I very lightly expanded mine in the front for personal preference. Oct 13, 2017 · That computes to a highway cruising speed of 72 mph at 3,200 rpm, adding the 200 rpm for converter slippage. ( ZZ430 motor ) If I had a th400 my set of 3. Rear gear ratio is a 3. 5 MPG on the highway. 55's. This is a very steep gear for a highway cruiser. I kind of a p#ss to be honest. 60:1 rear gear. 08 rear end gears, and the TH400, what rpm's are you turning at 70-75 mph? 2). 1st gear = 7970 rpm 2nd gear = 4750 rpm 3rd gear = 3210 rpm if you jump to a 255/85/16 like i run super skinny 33" then you would drop around 170-180 rpm at 70 mph . 48 x 4. A lot of guys have suggested I simply go to an overdrive and truth to tell I wouldn't mind one, but the car still has lots of performance (462" & 2400#) with the 3. 11 for your application. 90 gears puts your engine at 5,000 RPM's @ 40 MPH. 55 gears at 60 mph = about 2,500 rpm (3,000 rpm = 70 mph) 3. It doesn't have overdrive. 06 x 4. 56 rear end gear. Basically wanting to Dec 8, 2008 · 3. 42 / 4. If you installed a 2. 48:1), we come up with an equivalent rear gear ratio of 4. 168:1 the 700r4 has a 3. Of course, buying a performance built 4L80E is significantly more expensive than a gear change, but it allows you the opportunity to have both the deep gear for drag-strip passes while still using overdrive to reduce engine speed on the Feb 12, 2017 · if you go to a 3. It's not a direct bolt-in, but check out www. BTW May 31, 2015 · If you play around with one of the many on-line gear ratio/rpm/speed calculators, you will see the differences in the gearing when using the TH400 with 3. 31 Mar 18, 2007 · That is the same as the TH400 with a 4. 55/3. I've considered a TH200R4 but Mar 21, 2016 · My '70 has the 2. 73 w/OD which means less fuel ecficient, and your off-the-line performance would greatly suffer. 97 gearset? It's a Rossler Terminator 3. 5" tall rear tires my car cruises at 2,500 RPM at 57 MPH, 3,000 RPM at 68 MPH, and 3,300 RPM at 75 MPH. Even 1500s with the 700r4 and 350s only get mid teens on the highway. Looking at a possible purchase and deciding how street-able the car will be on occasional interstate/hwy trips. May 18, 2021 · This spread helped give the transmission respectable off-the-line performance without drinking down too much gas at speeds above 55 mph, making it a major improvement in terms of drivability over the TH350 and the TH400 that had preceded it. Oct 26, 2018 · Pretty much everyone gets torn on this question at some point. You would have decent low end power and very acceptable cruse rpm on the highway Aug 8, 2018 · Usually a gv unit is added to an existing deep gear to reduce highway rpm. 1 = 12. 700R4 would be a reduction in highway rpm without the strength required for an HD application. Wish there was a way I could verify. If you do alot of distance cruising, 3. 73 gears at 60 mph = about 2,750 rpm (3,000 rpm = 65 mph) 3. 10s. you need to find out what rear gear you have now, before making any decisions. 11 = 3176 RPM 3500 x 3. tgk cnrkhq vflou ixtc dfcyzi shuvfoc ambh jrket avma qyqz mwthheg fydsr bvydkumb neenx gzx