Today after having two days of rain, i took the blazre out in search for some mud, but only a few small puddles, after about an hour of trail riding, nothing hard at all, my tranny started to slip, after climbing a hill i stopped, then when i went to take off again it wouldnt shift into gear, i turned it off and let it cool down thinking maybe i overheated the tranny, after cooling it shifted into gear and got me back to civilization but after 2 miles on the highway it was slipping paired with a nice whine that sounded like a supercharger and started to smoke and you could smell burnt atf. Pretty sure its fried, odometer stopped at 196000 mi and i have no idea when it was serviced before i got it. Now i come to my question, how hard is it to rebuild a th 400? Do i need any special tools? Thanks.  

not really any special tools, just a spring compressor to get the pistons out of the drums for the lip seal replacement. they wine when the filter is pluged and or low on fluid, also if the filter tube came loose from the case. be sure the spacer under the filter is in place to keep the filter on the botton of the pan. I'd imagine a cooler line or something was spraying/leaking fluid on the exhaust making it smoke.  

i checked and it wasnt leaking, i few drops out of the inspection cover over the torque convertor.  Im going to drop the pan and change the filter and refill and see what happens.  

Prolly smoked a band or clutch. What a bummer!  

the 400's don't have a smokin band problem like the torqs and fords do.

be sure to make sure the tube is push all the way up. they kinda flop around but generally don't have problems.  

use some of that lucas treatment stuff. i had almost the exact same thing happen to my 400 years ago and like mud said it was a filter issue. give it a new filter and run b&m trick shift fluid in it less one quart for the lucas oil and i'll bet it's fine.  

I suspect it fried. Big tires and stock gearing can be tuff on a tranny. Also, they never came with TH400's either so if it has one, someone swapped it in.  

today after towing it home, i fired it up and was trying to back it into my garage, made it up my steep yet fairly short driveway, but as i reached the top it started slipping and kind of shuttering, i stopped and then it wouldnt go back into reverse.  I am going to drop the pan in the next couple days and replace the filter and fluid and hope that fixes it.  Also I put that lucas transmission treatment in it a few months back, and today someone was telling me that additives and stop leaks will sometimes plug up the filter and it wont be able to pump enough fluid, any truth behind that.  

yeah, it depends on the additive though. as long as there isn't a whole pile of black gritty crap in the pan I might be ok, some small metal particles is normal, but large chunks isn't. you could fire off some pics of the pan when you get off. then we all can pick on ya some more,LOL I never use a stop leak type stuff just a seal softener occasionally for someone who can't afford a rebuild kit.  

i stand by all lucas products. so    

I thought lucas made good products, i dont think it caused it.  I think what happened is, i had to change radiators, and the one i got from a friend was damaged, the bottom tranny cooler inlet on radiator was stripped, so i am running 2 medium size inline air cooled coolers, and i probably overheated the tranny and burnt the fluid and it plugged the filter, or that is what i hope happened. One thing for sure now is i will be putting in a temp gauge for tranny, and will go major overkill for cooling it, was thinking of mounting up this small radiator i have out of an old volvo and capping the lower and upper hose ports, and using it strictly for the tranny cooler, tranny fluid would be cooled by water that isnt heated to 200 degrees from the engine.  

Nothing is gained by over cooling a tranny. There is a lot of misconceptions here. What cause a tranny to fry is when you ride stall a lot as it is a big heat maker and with a THM400 below about 2300 RPM under heavy load you are riding stall. (it has two stall speeds one at a stand still and another when moving which is usually about 300 to 500 RPM higher) Sounds like you rig is running stock gears and cooking tranny and trying to super cool oil is not going to fix it because not that much oil flows thru that line to cool it right riding stall hard a lot. Deeper axle gears get it off stall quicker and require less torque across converter when stalled (so there is less heat) to provide same ground effort as taller gears. The PROPER way to cool it is to run fluid through radiator tank cooler first rhen a aux cooler. This provides max cooling and a more stable tranny temp. desired temp range for a warmed up tranny is about 160 to 200F with 180 being ideal. Running it cold can shorten life and increase power loss in tranny. Your tranny is likely toast and any efforts and resources spent to try to revive it would be better spent on replacing it or rebuilding it. If you what to cure this problem for good too, regear you axles as well and just stay in this loop.  

I wasnt looking to the cooler as my solution for tall gears. I am just going to stick to the radiator cooler and aux cooler. If the tranny is shot, i may pass up rebuilding it and look for a 700r4, that way with od I can gear even lower like 5.13 and with the 700's lower 1st i will get a better crawl ratio plus decent highway rpm. Snoman, if i go for the 700r4 will the np208 that i had with a th350 work with it. if not what is the typical t-case found with the 700.  

the 208 then after 87 the 241  

#19  
mudb8
Registered User


Member: 106114
Location: Estacada,Or.

 the low 3.06 and the .7 OD plays a large advantage for wheeling hwy cruising and crawling, consider how low you can get in the differentials and still haul down the hwy at 25 or 2800 rpm like the desired ratio using a 350- 2.52 1st, 400 and the 4l80-2.48, the advantage is healthy, even the reverse gear- 2.29 vs a 2.07 of the 350/400. then there's the standard 465 reverse for comparison.....6.09 what good is that in the muck? awesome crawler though.

with 5:38 gears in OD the crawl ratio is 3.77, gees....you could get into the 6's for the axles and still haul down the hwy and think about what that'll do for the off road ability and crawl ratio. It is 62.56 using a 3.8 in the t-case, and 5:38 gears.........using a 5.1 t-case it's 83.96.

all this means is at 70MPH with dinky 35" tires, 5:38 gears, in OD the rpms will be 2,530 RPM's, in that rpm range the overdrive is not going to be stressed and/or creating the disastrous heat from riding the stall regardless of horsepower. O' I know it was distputed, elswhere mostly by opinion, He say's/she say's, I did that he did this blablabla type of crap.

yep i was lazy and copied and pasted from another forum, I had figured the crawl ratio on....