slipping trans - help!

[turf]

hey folks,

the last day of my 3600 mile bus travels, the transmission started to noticeably slip. it was worse cold, and got better as i drove. i kind of limped home and.... now im looking into the problem.

it hard to read the stick, i filled about a gallon of atf in there this morning and tried to drive it. it drove better with the atf, less slipping, but it didnt want to change gears, and when you revved it, it slipped.

i pulled the plug on the pan to see whats going on. dark, thick, fluid came out at first, but when it slowed down, maybe it looked like a bit of the new was dripping thru.

it was full of fluid before i dumped in the extra gallon. when i drained it, the fliud came close to the top of my large oilpan. the drain plug magnet was covered with metal, both real fine shiney bits and larger flakes.

so now, do i try to flush with more fluid? do i drop the pan and clean it out?

do i line up a new trans?

what would you do?

[cadillackid]

that looks like a lot of clutch material.. is it slipping gears or do you think the lockup clutch bit the dust?



if in fact it did get low on fluid and started slipping.. it doesnt take long at all to glaze a clutch pack and that clutch will never hold right again..



while the 545/1545 has an external spin on filter there is also one in the pan.. the spin on is in the cooler lines so it isnt getting all the fluid so it is indeed possible for the pan filter to clog up,. there are 2 different kit numbers.. 1 for shallow pan 1 for deep.. since the AT545 and MT643 use the same filter kit.. id venture a guess that the 1545 would too..



and it would be worth changing it.. although in my experience it would be a temporary fix..



if you got home id probably drop the trans and get it built at a local shop vs find another one.. you get another used unit and now you are in thye same boat.. how long will it last? if you get yours rebuilt then you know what you are starting out with..



I honestly dont know if the 1545 can use a 545 rebuild kit for clutches or not.. the converter would be my biggest concern sionce it was specialized application.. maybe its the similar to an MT643 converter..

[turf]

it doesnt seem to shift.

maybe i get to 2nd, but then it slips. if i keep pushing, i gain speed, but get further from my driveway. i've driven it a mile, to the corner, where i can turn around and head back home.

shifting manually doesnt seem to do anything different the "drive".

i had no indication of problems until the last morning. i woke up and tried to leave the truck parking area, and it didnt want to.
i got it up to speed and made it the last 100 miles home.

i changed the spin on, external filter before my trip. i was surprised that it was under pressure at the time, but it blew a good amount of fluid out after i pulled the filter. but i remember thinking the fluid looked good. today was not the case.

the day before it failed, i was thinking how well it all worked. i was pushing 70mph thru utah and nevada. my usual speed is 67. i went up the continental divide in wyoming without much noticing it. pulled over, slept and then she didnt want to work anymore.

maybe that 101 coast was a lot harder on the trans than i thought.

[cadillackid]

long slow grades are the hardest on any transmission.. gears are inherently inefficient.. the harder they are worked the more heat they make even with a lockup turned on.. .. if the fluid was low at all.. things would go real bad real quick.. as line pressure might run low.. or if engine rpm was low but load was very high.. even a small slip would make a ton of heat.. which could boil the fluid out the vent..



I boiled a bunch of fluid out on I84 in wyoming with my super ior and its AT540.. I started to smell warm trans fluid and pulled over to find fluid coming out the vent.. I got lucky I never sucked any air so the clutches didnt burn up..

[Albatross]

In my experience, those symptoms are usually indicative of a dead tranny. I would say that it's better to go ahead and park it and budget and plan for a rebuild or replacement, because you're going to need it sooner than later. Servicing a tranny that hasn't been taking care of is a good way to kill it earlier than it should have died; but the result is usually one that can be rebuilt better than one that hasn't been touched. Or cheaper/easier at the very least. Once you've got a refreshed drivetrain, you can feel free to service it as recommended, but if you don't, then trying to play 'catch-up' at a later date will likely repeat what you're experiencing now.

[turf]

dang, that is disappointing.


i replaced the trans a few years back. it was a at545 swapped to its bastard brother the at1545. i'm guessing i have about 50k miles on this trans. most of those, towing 5-7000 lbs

it was new old stock, still in it shipping container when i purchased the trans.

ima drop the pan, change the internal filter, finish the flush, and fill it back and see where its at.

im ready to swap to a better trans..... something with overdrive and more towing/hp capacity. what do i need to start looking for?

i have a '93 all mechanical 6bta looking for fuel mileage and better highway cruising with my 4.7 rear dif. allison 1000? 2000? 3000?


tuning side note here - anyone ever pull their fuel plate? im considering it now. seems that is the limit when you're on the highway, foot to the floor.

[magnakansas]

545 kit is supposed to work. 4l80e direct clutch parts supposedly interchange for the Allison 545 fourth gear clutch, This means - supposedly - by using thinner steels, fiber rings, clutch piston, instead of 5 plate, you might be to get 7 plates. There is supposed to be a steel clutch piston with a more effective seal. Place called DACCO seems to be able to rebuild converter.


In addition to the 545 rebuild kit there is a converter seal you will also need - it is not in the kit.

Double check all this information from at least two other sources.

I might be full of bad/ misleading information

Turf call me 7852077600

William

[s2mikon]

Excessive heat kills the vast majority of automatic transmissions. If you don't have a transmission temperature gauge how do you make driving adjustments as you drive? Most of us would not drive a large vehicle without a water temp gauge, yet we have no problem with running an Allison without a temp gauge. Most school districts buy buses on cost. Add on's are looked at in alphabetical order. A as in A/C comes before T as in transmission temperature gauge. Most of the responsible people in purchasing have no business ordering buses. Transmission temp gauge? My Lexus doesn't have one, so must not be needed. V8 engine? Has to be better than a 6 cylinder right? 20-30 years ago the person that ordered these vehicles knew the business well and ordered accordingly. So now it is up to those of us to do those adds that were really needed. I glad that you got home with it and it didn't leave you stranded in bumb deal Egypt. I personally would not waste my time and money changing the fluid, filter ect. It is wrench time now. You have some choices to make now so get out the calculator and see what fits your budget. The 5.9 makes it a lot easier to make swaps with than some other power plants.

[turf]

i doubt it got hot.

i have a temp gauge, however it isn't functioning. the wires have come loose from the sensor in the pan and i havent fixed it yet.

i also have a big trans cooler i installed a few years ago. ever since i got the cooler, i don't think i've ever had the trans hot. im lucky to get up to operating temps. 160-180 would be normal pan temps, after i installed the cooler. more 160s than 180s

i'll drop the pan tomorrow and post some pics, i bet its full of clutch material.

[turf]

if im replacing......

i'd rather not rebuild what i got. i jerry rigged this one to work, rebuilding it just kicks impending doom down the road.

i also want better fuel mileage! right now im at 7.5mpgs, getting up to 12mpg or so would pay for the trans in fuel savings pretty quickly. i've heard that peeps with overdrives get that kind of mileage.

on my last trip, 12mpg would have saved 180 gallons of diesel.

3600miles/7.5mpg =480 gallons
3600/12mpg = 300 gallons.

cali diesel was ~$5.50 *180 gallons - i could have saved $990, with 12 mpg.

[Albatross]

Originally Posted by turf

if im replacing......

i'd rather not rebuild what i got. i jerry rigged this one to work, rebuilding it just kicks impending doom down the road.

i also want better fuel mileage! right now im at 7.5mpgs, getting up to 12mpg or so would pay for the trans in fuel savings pretty quickly. i've heard that peeps with overdrives get that kind of mileage.

on my last trip, 12mpg would have saved 180 gallons of diesel.

3600miles/7.5mpg =480 gallons
3600/12mpg = 300 gallons.

cali diesel was ~$5.50 *180 gallons - i could have saved $990, with 12 mpg.

Best I ever got in my 6.2L w/ 4L80E in my 24' Minibird was around 11-13 mpg; and I suspect that most of that was because I was driving downhill the whole way out of the Ozarks down into the Texas Gulf Coast. Most of the time I remember averaging around 9 MPG while weighing in at around 13K lbs.

[s2mikon]

When you changed the spin on and it was under pressure that was because the cooling circuit was plugged at the filter. When that happens you are not getting fluid through the cooler so the transmission will get hot. Very hot. If your coolers went through a previous transmission failure then they were compromised. You can flush them till hell freezes over and they will still have trash in them. I don't know the particulars on your bus, weight, what are you pulling behind you and driving speed ect. but I don't think that you will see 12 mpg. Would be nice but I don't see it happening.

[cadillackid]

Originally Posted by s2mikon

When you changed the spin on and it was under pressure that was because the cooling circuit was plugged at the filter. When that happens you are not getting fluid through the cooler so the transmission will get hot. Very hot. If your coolers went through a previous transmission failure then they were compromised. You can flush them till hell freezes over and they will still have trash in them. I don't know the particulars on your bus, weight, what are you pulling behind you and driving speed ect. but I don't think that you will see 12 mpg. Would be nice but I don't see it happening.

good call on the pressurized cooler lines.. makes 100% sense.. the symptoms that trans has indicates it was hot..



I do have to wonder what the engine RPMs were climbing the hills.. the original AT545 had a bad pump issue.. and that is it didnt make full line pressure until you were over 2200 RPM at the pump.. which is the engine.


typically Loose converters on these meant you were almost always revving above 2000 RPM and putting the maion line pressure into the range where you get good holding pressure on the clutches..



I wonder if the lockup converter on this actually prevents the pump from spinning fast enough esp on accelerations in 3rd / 4th to build enough pressure to hold all of the clutch packs..


lots of material in the pan in a short time is again something that indicates slipping.. a blown internal seal can reduce fluid pressure (and cooler flow) as well as holding power on the converter clutch as well as the main clutch drums.. if you are pulling a long hill and the RPM starts dropping back yet the unit stays locked up and doesnt downshift.. its a prime situation to create a small slip.. a small slip will build Big heat and fast.. the hotter the fluid gets the lower the pressure will be and less holding power.. and well you can see where this leads.. you may not even know as it slips a little more and the engine revs a bit.. makes you assume the converter unlocked when in reality its burning itself up..





what do you change it with?


if you want overdrive and are planning to haul heavy loads / pull long grades with a heavy bus, you have a couple options..


1. have a 1000/2000 Built to do the job.. a used transmission will be another worn out unit from school service that would last most people but not those with high demands... this optrion is obviously not cheap.. I had my allison 1000 Built heavy in 2017 and i can hnestly say your wallet wont be happy esp in 2023 to have one built..



2. go with a reasonably fresh 3000 series.. the 3000 series is a much heavier transmission.. everything is Bigger.. its an SAE2 bell (there wasnt an SAE3 option) so alot depends on your housing and ability to get / make new spacers for the hiub and the right flexplate for a 6BT (that has the fuel turned up). the 3000 is a beast but may be what you need for the use case of your bus..

[turf]

i'll probably get a price for rebuilding this at1545 and compare it to an allison 1000 swap.

a used 1000 is my budget.
is it the redbyrd thread that has this swap? i got some reading to do.

i havent done much to the 12v as far as horse power. the afc mods i've done say ~30hp. i have a 190 pump +/- 30hp. the bus is 19k lbs + 5k towing.

if i can support the bus at 80mph with my 4.7 gears, i'll stop playing with the 12v.

i havent pulled the pan yet, maybe tomorrow. i got a feeling its full of sludge.

the pressure comment from s2mikon is probably dead on. thanks for that insight.

heat wise, i was driving off the info from the egt gauge.

[s2mikon]

Here is something to look at that I have found to be very accurate as far as how much horsepower it takes to go 60 mph vs 70 mph and the fuel use to do the same. It works out on my bus and my sons crown. https://www.prevostcommunity.com/PDF...%20economy.pdf

[turf]

what a great guide!!! thanks

the quick read says 300hp will get me 80mph, 400-450hp will climb hills like i like.

ima have to read it a bit slower and take it all in.

[s2mikon]

If you tow a car or jeep behind you just add the automobile curve and the coach curve and it is about right.

[cadillackid]

redbyrd transformation is my swap thread.. its a bit different than yours..



if in fact a clogged cooler triggered the failure it bodes well for a rebuild (with updates) of the 1545.. and maybe install an external cooler with a fan and have longevity..


rebuild shops can do some purposing of the valve body, clutch packs and even shift schedule (lock up in 2nd perhaps).. to better handle your horsepower and use case.



a used 2000 series will be an easier find with an SAE3 bell to match your engine.. you would simply reinstall the bits from your 545 to the engine and an SAE3 1000/2000 series will bolt right up..



your electronics would be simpler than mine as your engine is purely mechanical so you would get a throttle box from one of the swap companies.. if your 6 BT max revs in the 2600-2700 rpm range most TCMs from diesel school busses will give you decent shift patterns right off..



most used allison 1000s found online are GMC duramax and use a GMC bell / tail setup which is different than a bus/truck.



I went the route I did knowing I was going to tune the motor in the future to push 325-350 Horsepower.. a stock 1000 / 2000 without SEM on a heavier vehicle really doesnt handle a ton of torque / power.. the way the modern units take so much power is by way of SEM (essentially when the trans shifts it tells the engine computer to back off the power and when the shift is completed the trans releases the power hold).. transmissions are most vulnerable to failure during their shift process..



just like a manual trans.. people who stomp on the gas too quick before the clutch is out all the way tend to burn up their clutches quickly vs those who stomp after the clutch is engaged fiully.. of course on mechanical diesels there is no such thing as SEM.. (it didnt really come along until 07/08 )

[La Camioneta]

Originally Posted by turf

dang, that is disappointing.


i replaced the trans a few years back. it was a at545 swapped to its bastard brother the at1545. i'm guessing i have about 50k miles on this trans. most of those, towing 5-7000 lbs

it was new old stock, still in it shipping container when i purchased the trans.

ima drop the pan, change the internal filter, finish the flush, and fill it back and see where its at.

im ready to swap to a better trans..... something with overdrive and more towing/hp capacity. what do i need to start looking for?

i have a '93 all mechanical 6bta looking for fuel mileage and better highway cruising with my 4.7 rear dif. allison 1000? 2000? 3000?


tuning side note here - anyone ever pull their fuel plate? im considering it now. seems that is the limit when you're on the highway, foot to the floor.

Coupla things you can do.

First is retorque head bolts.
Injector pump timing to 16*
#8 fuel plate
Killer Dowel Pin kit
3K governor spring kit
Mack rack plug
Wire wastegate shut or pinch boost reference line.
Boost/pyrometer gauges.

I swapped in a used 2000 series from a 6.0 PSD bus. Had to add a TPS, sent tcm to transmissiontuner.com and a custom low-stall converter to match the 5.9. Pretty satisfied and I think a bigger turbo with more bottom end will clean up the hunting it does for lack of power.

Averaging 8.5mpg interstate running 75+ as much as I could.

Didn't want to put any more into the bus before the Guatemala trip so haven't changed turbos, but that's next. At 13000# 4.11s on 11R22.5 she will run mid-70's but struggles with bottom end torque. Going to go with whatever the Power Driven Diesel guys recommend, don't care if it runs out of boost at 3k, that's well over 80mph.

[turf]

Originally Posted by La Camioneta

Coupla things you can do.

First is retorque head bolts.
Injector pump timing to 16*
#8 fuel plate
Killer Dowel Pin kit
3K governor spring kit
Mack rack plug
Wire wastegate shut or pinch boost reference line.
Boost/pyrometer gauges.

I swapped in a used 2000 series from a 6.0 PSD bus. Had to add a TPS, sent tcm to transmissiontuner.com and a custom low-stall converter to match the 5.9. Pretty satisfied and I think a bigger turbo with more bottom end will clean up the hunting it does for lack of power.

Averaging 8.5mpg interstate running 75+ as much as I could.

Didn't want to put any more into the bus before the Guatemala trip so haven't changed turbos, but that's next. At 13000# 4.11s on 11R22.5 she will run mid-70's but struggles with bottom end torque. Going to go with whatever the Power Driven Diesel guys recommend, don't care if it runs out of boost at 3k, that's well over 80mph.

wow, better mileage, higher speed!!!

i have a #100 fuel plate now. it was stock. my understanding is the next size up is a 0 plate, or none at all.

ima try and pinch off the turbo and see what happens, i never get over 15psi.

3k spring kit makes sense if i want to go faster. im considering it.

my biggest trouble is high egt climbing hills. im in the low lands of colorado and all i do is climb big grades.

i wanted to upgrade my front suspension, but transmission looks to jump line.

the cat guide from the earlier post makes me think i need to up the hp, to make it a happy hill climber.

maybe bigger injectors? try and boost from ~200 to 300 territory.

i''ve got the gauges.

on my trip i tried tuning my afc. i'd make a change first thing in the morning and run it all day. after about day 4, i think i have it dialed in pretty close.

the smoke screw gets you off the line.
the star wheel takes you thru the gears.
the fuel plate seems to limit top end cruising, kinda why im ready to try and pull it to see how it behaves.

if i rebuild the 1545, then maybe i'll do the 3k gsk. dont think i'll need to with a trans swap to overdrive.