Marty DB Posted July 5, 2013 Share Posted July 5, 2013 My husband and I just purchased a '91 Toyota Dolphin and we love it. However, it's getting only 10.5 miles per gallon which is terrible. We expected so much more from this vehicle. Any thoughts on how to improve that? Thanks. Quote Link to comment Share on other sites More sharing options...
Maineah Posted July 6, 2013 Share Posted July 6, 2013 How fast are you driving? !3-16 is more in line. Tune up and filters might be in order. Quote Link to comment Share on other sites More sharing options...
Marty DB Posted July 6, 2013 Author Share Posted July 6, 2013 Had all that done. All is in order except the gas mileage. Might be driving too fast......... Quote Link to comment Share on other sites More sharing options...
linda s Posted July 6, 2013 Share Posted July 6, 2013 Had all that done. All is in order except the gas mileage. Might be driving too fast......... 60 mph seems to be the sweet spot on these rigs. If your going 70 or more then 10.5 miles per gallon sounds about right Linda S Quote Link to comment Share on other sites More sharing options...
douglitas Posted July 6, 2013 Share Posted July 6, 2013 we took a few short trips when we first got our rig (89 Seabreeze) and were disappointed with the 11 mpg we got. Later we overhauled the cooling system (new radiator, water pump, fan clutch). Then we took it on a few longer trips and we consistently get 14 mpg. Quote Link to comment Share on other sites More sharing options...
zero Posted July 6, 2013 Share Posted July 6, 2013 My husband and I just purchased a '91 Toyota Dolphin and we love it. However, it's getting only 10.5 miles per gallon which is terrible. We expected so much more from this vehicle. Any thoughts on how to improve that? Thanks. I've met many 21 foot Toyota owners with V6s and auto-transmissions that reported 10-12 MPG when trying to maintain 65-70 MPH. 13-15 MP when they slowed down. I don't know if that applies to you. If the engine itself is running OK - there are no mods you can make that will improve it much. Engine timing and running temps have minimal effects on MPGs. In fact, a hot running engine usually gets better MPGs and a colder engine a bit less. Stick your finger inside the tailpipe and see if it comes out clean or covered with black soot. If there's any soot in there - the fuel injection system is running too rich. Also verify the engine is warming up properly. It would also behoove you to jack the wheels off the ground and check all for any undue drag. You also might want to verifiy your odometer is telling you the truth when calculating fuel mileage. Verify with a watch and milemarkers on the highway and/or a GPS. One thing you're not going to fix with an automatic trans is the constant 15% slippage and waste when driving at highway speeds. More modern rigs eliminate the torque converters when driving highway speeds. Not the Toyota though. Quote Link to comment Share on other sites More sharing options...
linda s Posted July 6, 2013 Share Posted July 6, 2013 I thought the locking torque converter in the A340E transmission eliminated much of that slippage waste and 15% sounds high even for my non-locking A43D transmission. Linda S Quote Link to comment Share on other sites More sharing options...
zero Posted July 6, 2013 Share Posted July 6, 2013 I thought the locking torque converter in the A340E transmission eliminated much of that slippage waste and 15% sounds high even for my non-locking A43D transmission. Linda S If his rig has a locking torque converter - then you are correct and it has NO slippage if working correctly. If not - any automotive torque converter works at 15-18% slippage when crusing at highway speeds and more when under a hard pull. I was thinking the older trans. Maybe he needs to verify if the converter bypass (lock up) is actually working. Quote Link to comment Share on other sites More sharing options...
Maineah Posted July 6, 2013 Share Posted July 6, 2013 All the V6's had lockups Quote Link to comment Share on other sites More sharing options...
linda s Posted July 6, 2013 Share Posted July 6, 2013 I did discover though that the lock up doesn't work unless you engage overdrive. I don't have one on my Toyota but I do on my Nissan so good to know. Linda S Quote Link to comment Share on other sites More sharing options...
zero Posted July 7, 2013 Share Posted July 7, 2013 All the V6's had lockups No they did not. I know of many 1991-1993 V6 Toyota dually trucks with V6s that were built without the lock-up torque-converters. Toyota part # 3200-35080. When it comes to RVs like Dolphins - I have no idea what specific types of transmissions were used. MaineAH - where do you find any documentation stating that "all Toyota V6s with automatic transmissions" have lock-ups. I know that is not true but I do wonder where you got that info. I DID notice that if I ordered a rebuilt auto trans for a 1991 dually 1 ton - it is $250 cheaper then if for a 1991 1/2 ton. I suspect the cheaper price is due to the lack of a lock-up system - but I do not know for sure. When GM built overdrive automatic transmissons for RV use late 80s to early 90s -the lockup was either not used - or if it was - it was wired up to work differently then in a lighter vehicle. I don't know if Aisin did the same with auto transmissions used in Toyota RVs. But with GM - there was no 4L60/700R4 offered without lockup. They'd just use a TH-400 instead. In the case of Aisin transmissions in Toyotas, they sold A43Ds with and without lockup converters. What got used where, I do not know. GM had a nice feature of making it easy to get lock-up in 3rd gear (1 to 1 ratio) for HD use in some. When a heavy underpowered vehicle only has lockup in 4th-OD, it often rarely gets used (depends on the gearing and where driven). Quote Link to comment Share on other sites More sharing options...
Nam Posted July 10, 2013 Share Posted July 10, 2013 I belived my '90 Itasca is pretty well tuned, the dealer just did a Head Gasket with most new parts at the head...but I constantly get 13MPG going about 60MPH...a little low in my opinion but I don't think there is much I can do to improve that. Any idea? 10.5MPG is quite low...but depending on how fast you drive Quote Link to comment Share on other sites More sharing options...
Maineah Posted July 10, 2013 Share Posted July 10, 2013 "No they did not. I know of many 1991-1993 V6 Toyota dually trucks with V6s that were built without the lock-up torque-converters. Toyota part # 3200-35080". The topic was motor homes not UHaul's. Your the web guy look it up. 4 cylinders did not have O/D because the engines did not have enough guts to keep it from unlocking at highway speed. The GM TH 400 was the preferred MH trans because the early 700R4's did not hold up and were constantly locking/unlocking and down shifting the first year they were out there were 83 TSB's in an attempt to fix them they really didn't get it together until mid 90's Quote Link to comment Share on other sites More sharing options...
DanAatTheCape Posted July 10, 2013 Share Posted July 10, 2013 My 93 winnie warrior also got bad mileage. i had an intermittent check engine light. These are pre OBDII computers so the codes are not nearly as good. In my case it was the oxygen sensor. I tried several mechanics & even a toyota dealer - who eventually threw the O2 sensor at it - now I get 14. With reasonable driving, u should get 14-15, a little lower in town & on forest service roads. 10.5 - assuming your math is good, is too low. Quote Link to comment Share on other sites More sharing options...
Maineah Posted July 10, 2013 Share Posted July 10, 2013 I had a tendency to push my 4 cylinder on the highway (65 and maybe higher) and doing so I got 13-14 max. They are bricks and the drag goes up with speed rapidly. Quote Link to comment Share on other sites More sharing options...
zero Posted July 14, 2013 Share Posted July 14, 2013 "No they did not. I know of many 1991-1993 V6 Toyota dually trucks with V6s that were built without the lock-up torque-converters. Toyota part # 3200-35080". The topic was motor homes not UHaul's. Your the web guy look it up. 4 cylinders did not have O/D because the engines did not have enough guts to keep it from unlocking at highway speed. The GM TH 400 was the preferred MH trans because the early 700R4's did not hold up and were constantly locking/unlocking and down shifting the first year they were out there were 83 TSB's in an attempt to fix them they really didn't get it together until mid 90's I'm not sure what earns me the title of being a "Web guy." I maintain a few business Websites but don't spend much time seeking reliable data on the Web. I probably spend more time here then anywhere else in cyber world. You wrote " All the V6's had lockups." That is not correct. Certain V6 RVs may of only had lockup with automatics but you did not state that. In regard to the GM 700R4/4L60 - the transmissions were horrible with no known good fixes until 1986. That's why so many were converted to TH400s and also why changeover kits were available along with mechanical modulators so the TH400 could be hooked to the 700R4 TV cable. The lock-up cycling on and off was a minor issue and easily fixed - even on the first year of production. Many got manual toggle switches wired in. Much more problematic were things like the too small front pump blowing out seals, inadequate 3-4 clutches, inadequate brake-band servo, piston-seal failures, over-running clutch failures, planet pinion failures, thrust washer failures, etc. There were over 50 GM service bulletins with attempts to repair in the first four years. After 1986, the entire trans was redesigned. Different case, different valve body, different drums. By 3001 when the 4L65E was in use - it was a good trans. A good rebuilt for a HD 700R4 usually requires a 1987 or newer case and many of the piston seals and the planet pinions from the 4L65E. I just got done doing one in a 1986. I used a 1991 4L60 and 4L65E planet pinions and unitized piston seals. The reality is though that the 700R4 or 4L60 is just a reworked TH350 and never intended for a heavy GVW. The TH400 or when reworked -the 4L80E is the auto trans of that vintage suited for RVs. Funny though to think the TH400 was first designed for a car (Buick Riviera). I still have one in my scrap yard. TH400 with a two-range torque converter and a Dana 60 rear axle. Pretty amazing that cars were once built that heavy. Quote Link to comment Share on other sites More sharing options...
McG. Posted August 7, 2023 Share Posted August 7, 2023 Hello, I just stumbled across this website. I hope I'm doing this right. I'm 71 and thinking about making a 90's Toyota Rv. My last and only transportation. So much more I'd like to ask later. Thanks Quote Link to comment Share on other sites More sharing options...
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