Transmission Overheating

[danpemby]

We have an 86 Sunrader. I have owned her for almost 3 years and the last 2 weekends are the only trips the Wife and I have made in her. Loaned it to my son right after I got her and he blew the HG, so she has sat for awhile. I have many other questions that i will post in the proper threads later.

Ok so trip one. We drove about 65 miles through part of the Mark Twain NF across winding roads with ever changing grades. She had some troubles on the ups (Maybe 500 - 600 feet accents) doing maybe 20MPH with passing gear kicked in. I noticed the temp gauge never reached half way (I think it may need attention) but we started smelling something. When we finally saw a service station we pulled in. checked under the hood and radiator fluid was fine, oil was 1/2 QT low (added) and tranmission fluid was fine but dark and smelled burnt. Also it appears the fuel gauge need attention as it showed 1/2 full, i put in less than 5 gallons and it was full. Fuel gauge still read 1/2. We were only 5 miles from our destination of Meremac Caverns so we went on down and parked her. On the way home we decided to take a more level route. On acceleration from a stop, she would "Chatter" really bad until she was rolling and then ran fine. Got her back to the drive way and she did not make it all the way up before smoke strated pouring out.

Changed the tans fluid and filer, replaced with synthetic.

Second Trip. We decided to go nat as far but again we have to go through the mountains. (Yes I know the Ozark Mountains and not that big) This time she was tooling along up the grades without much difficulty. We even hit the highest point in MO at 1700 ft. On the way to the campground, she started the "Chattering" again from a stop. I checked the fluid and it looked fine this time. She rested a couple days and we started our trip home. Well when i put her in reversed to leave the site, she hesitated, no the engine, the trans. Gave her some gas and she started rolling. Same thing from every stop. Going back up the grades we started smelling the trans fluid again, so this time i stopped for a while to let her cool. 2 stops later i put her in gear and she was slipping really bad. i could only muster 35 MPH before the engine would rev and no more power tranfer. I looked back to see a line of cars way back because of smoke pouring out. Pulled into a station that was closed but they had a hose. I hosed down the trasmission radiator for a while and then felt it. It was cool to the touch. Got underneath and hosed off the transmission, she cooled down. Got back in and started for home, 15 miles or so. Still slipping. Oh and now no Speedo. Got her home and parked her.

While this is a long drawn out story, my question is: Could the ports to the radiator be clogged and no fluid getting in? If so how can I check to see if there is fluid passing trough? If it is working, what else can i do to try to remedy this?

Thanks

Dan

[Shoprat]

Howdy Sir.

I hate to say this, but it sounds to be that your tranny needs to be rebuilt. Just my opinion.There's a fella on here, I think he goes by the nick Mineah, that is a ol' tranny man from way back, if I remember correctly. Maybe he can jump on this one.

[danpemby]

I was kinda afraid that was the case, I found paperwork showing it was rebuilt maybe 8 months before I got it. I started calling the local Trans shops here in town, and have ran into the same problem that kept her off the road with the HG. Nobody wants to mess with a motor home. Looks like I have to yank it out myself and take it in :-(

[Maineah]

Sure sounds cooked to me, where was the smoke coming from? If it was rebuilt by a reputable shop they may stand behind it. Most likely the forward clutch pack is bad if it chatters from a stand still also the converter is suspect if it was getting that hot. I guess what I’m saying you need a complete overhaul. There were some issues with the surface in the rear of the transmission where the governor rings ride so who ever does the work for you ask them to be sure to have a good look at the case. There was an after market bushing kit made for those transmissions where the governor fits so you would not be faced with buying a new case to repair it.

[danpemby]

I never really saw the source of the smoke, Just the effects. The rebuild was done in Florida, i live in small town Missouri. I am going to have a rebuilt trans put in as no one here will even look at it (no way to lift it)

Ok so next question: Is there a stronger transmission i can just bolt on in place of the A43D? I know I will be adding a trans temp gauge before she rolls again. Anything else i should consider before I make the purchase?

Thanks

Dan

[turtle]

Get a transmission oil cooler installed when you get the transmission put in.

The 4 cyl autos are very weak for use in motor homes.

Late model manual gearboxes seem to hold up better though some people are on their original automatic after more than 20 years of use.

[danpemby]

It does have a cooling unit. I assume anyway the thing that looks like a radiator, that sit in front of the actual radiator is what your speaking of. I was wondering if oil was actually pumping through it because when the trans was still hot, and the motor running, the unit was not hot to the touch. Is it possible the trans oil pump stopped working (Does it even have one?).

Ok, quotes are coming back in the 1250 -1500 dollar ranges for a rebuilt. I did get a quote from Midwest recyclers for 500. but I am sure that is just used, not rebuilt. I think it does have a warranty thou. Guy stated that the unit has 78K on it. Got me to thinking that My rig has 107K and if i could get 25-30K out of it I could start looking for a rig with a manual Transmission. Yeah i know, i am being cheap but the check for the head gasket and timing chain still has wet ink. LOL

[Maineah]

Probably not a bad price. Have you tried a truck garage they should have the head room to lift your Toyota. If it was moving the pump was working. You probably have a small cooler mine did and it has been replaced with a larger Hyden cooler. They are looped into the radiator cooler as will it just gives the unit more area to the shed heat. Basically the fluid is from the line pressure circuit and it just dumps back into the transmission pan so there is little or no pressure only the resistance of the coolers and the pipes. Once you get the transmission repaired you will need to clean the coolers and the lines they will have metal in them from the old trans. The best method would be a flush but you can do it with solvent and air pressure. Check in the phone book and call a few transmission shops and ask if they are set up to do motor homes many are.

[danpemby]

There are good and bad things about living in a small Midwest town:

1. We are in Ford Country, meaning there was only one shop that worked on them there foreign cars. (He would not even touch my motor home when the HG went)

2. Called every Transmission place in the phone book, closest place that will work on a MH is 50 miles away.

3> New mechanic in town did finally agree to fix the HG, and although he did not want to, reluctantly agreed to replace the tranny if i get one. (pitfalls of having a new business I suppose)

I will look into the larger cooler

Thanks everyone!

[Maineah]

Wow too bad no one is interested in fixing it. I guess a Toyota is a scary thing if you only work on Fords! What the hey it maybe a great experience for them to see what it’s like to work on the best selling vehicle in the world. Well good luck be sure to clean the cooler lines out. I guess it’s pretty much the same thing here in Northern Maine if you have a skidder you’re are golden they know how to work on them!

[danpemby]

Well I believe i have found the root cause of the problem. I started looking though all the paperwork i have on the MH. Last two owners kept all receipts. Transmission was replaced twice in the last 5000 miles.

Upon the first replacement, they installed the cooler. I went to look it over and noticed they bypassed the radiator all together. This is a small cooler and should be a supplement to the radiator, not a replacement!

I think i am going to install a larger cooling unit either a Hayden Transaver plus 1678 or a Long Tru-cool 4589 and route it back through the radiator.

That should solve the problem.

[Maineah]

Agreed, hook the radiator cooler back up and add the biggest cooler that will fit. You also might also notice where it is shifting when you get it fixed if it is shifting too soon that will make it run hotter. It all so sounds like some one did not do a real good job on the first overhaul.

[DanAatTheCape]

I would hook up the radiator AND the cooler - also since you have had so much trouble, I would consider adding a temperature gauge for the transmission.

Since you have smelled burnt transmission fluid, at a mimimum I would change the fluid. You may have to get a transmission overhaul - I would definetely spend the time to find a real transmission man (not your average tranny shop) - you will have to talk to a lot of people in the car business to seek him out - many dealers have a real tranny man who they farm work out too - good luck getting them to open up and tell you.

I bet the parts people know who really is good - (if you can find real parts people).

[beehaven]

Whoa, dude! I am having my 1986 automatic tranny rebuilt. The mechanic alluded to the inadequate cooling system for the tranny inside the radiator. (The outside fins are for the air-conditioner). Toyota just about used up all the space in the radiator area, but the mechanic found he could squeeze in a small transmission cooler to pre cool the fluid before the radiator.He also installed a stronger torque converter . The only thing I know about these automatic transmissions is that it sure gives you a sick feeling when they fail.My experience with Japanese radiators is that they can partially fail because the water galleries are so small. Only a hand held heat detector can reveal that flaw.

Edited November 22, 2008 by beehaven

[Maineah]

These transmissions are not ultra complex the only thing unusual about them is they are all clutch transmissions (no bands). They were used in a number of cars and trucks Volvo, Jeep, etc. as well as all rear drive Toyota's. We as motor home users are asking a lot due to the weight and wind load so it’s best to take care of them add coolers, flush the old fluid at least every 30K not just drain the pan and use synthetic fluid. They should last 100k with proper care but I can’t stress the added cooler ideal more, the bigger the better. It’s converter slip that makes them hot and it is not just Toyota's all motor homes are subject to huge wind resistance an arrow goes a lot better then a brick. Years ago when I was in the transmission biz I would not guarantee a motor home rebuild 10 feet unless we added a cooler most did not have one.

[nibs]

I'm gonna jump in here, everything said has been accurate as far as I know, but I would like to offer some experience gained from having to rebuild my 740 Allison $15,800.

When climbing, shift down using the shift lever, & if you have overdrive, only use it on the flat, Maineah might give the best speeds to shift down for each gear (I have a standard).

Auto tranny/s are stupid, all they know is to get into the highest gear they can. If you do the thinking you can out smart them and keep them much cooler. If you have an ect control engage it, it makes the shifts at a higher rpm. If the tranny is shifting back and forth shift down, if the engine is pulling really hard shift down, that helps both tranny and motor. If my gas pedal is floored and we arent accelerating I shift down, even if it means slowing down a bit to stop overreving, You are pushing a small rig really hard, so help it out if you can.

Tony

[Maineah]

I'm gonna jump in here, everything said has been accurate as far as I know, but I would like to offer some experience gained from having to rebuild my 740 Allison $15,800.

When climbing, shift down using the shift lever, & if you have overdrive, only use it on the flat, Maineah might give the best speeds to shift down for each gear (I have a standard).

Auto tranny/s are stupid, all they know is to get into the highest gear they can. If you do the thinking you can out smart them and keep them much cooler. If you have an ect control engage it, it makes the shifts at a higher rpm. If the tranny is shifting back and forth shift down, if the engine is pulling really hard shift down, that helps both tranny and motor. If my gas pedal is floored and we arent accelerating I shift down, even if it means slowing down a bit to stop overreving, You are pushing a small rig really hard, so help it out if you can.

Tony

Yes you are right down shifting when the engine is laboring will make the trans run cooler because the converter can keep up with the load. The shift points are adjustable via the control cable on the Toyota transmission and if it shifts too quick in needs to be adjusted. If the trans is shifting back and forth from OD to direct it's time to turn it off until it will stay in OD (usually a nice flat road) Like nibs says slow down on the hills a use a lower gear just grab the shifter and crank it back a notch. Too bad about your Allison that's more then I payed for my car!

[fire362]

OK, even though I can't afford it, I need to put a tranny cooler on. I have 109K on mine. Can I get suggestions on what kind / size of cooler, where to mount it, and what type of trans. temp gage to get. I'm no mechanic and need "directions for dummys" suggestions please. Can you give me a cost that you think I'll have to pay. Yes, someone else will be putting it in.

Ken

1986 Toyota Sunrader 4X4

[Maineah]

Most auto parts stores have cooler kits if you can get it between the grill and the A/C condenser put the biggest one in you can. I have even put them in front of the fan on the inside of the radiator (if there is room). The parts store should have temp gauge also, the electric ones are the easiest ones to put in. You'll need to look at you cooler lines the highest one on the trans is the hot side (pressure side) follow it to the radiator cooler then remove the return hose (the one that does not come from the pressure side) from the cooler and return line and put your new cooler in between. The kits come with a hand full of parts needed to install the cooler.

[Supurcar]

Yes you are right down shifting when the engine is laboring will make the trans run cooler because the converter can keep up with the load. The shift points are adjustable via the control cable on the Toyota transmission and if it shifts too quick in needs to be adjusted. If the trans is shifting back and forth from OD to direct it's time to turn it off until it will stay in OD (usually a nice flat road) Like nibs says slow down on the hills a use a lower gear just grab the shifter and crank it back a notch. Too bad about your Allison that's more then I payed for my car!

I have an automatic/OD in my 1987 Sunrader, if I am on the freeway in say third gear I can get it up to maybe 65-70 and it will go into OD, but fails to pull in OD and will gradually slow down thus forcing it to go back into third. Very rarely can I have it pull in OD, I am not sure if this is common or if OD is for downhill or very flat roads. What I do is if it is shifting a lot I will stay in third and turn the OD off, along the lines of what you both suggested, let it rev rather than bog.