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Advise please. Transmission took a dump

U

ugly

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I have a 72 blazer, 454 with th400/205, locked 4:56 14 bolt/Dana 44

The trans leaks everywhere. Stopped at my brothers house for an hour and left a quart of ATF on the ground. Time for a change. I would like to get the RPM down while on the highway and keep the off road capability. Any ideas?

I'm sure it has been discussed many times, if you can help me find a thead with the info, that would help too.

Cheers.
 
Manual = NV4500
Automatic = 4L80E

Both require a level of converting but both are stout in their stock form and have overdrive. I run the SM465 but that's because I don't have a NV4500!
 
As mentioned.. 4l80e for the auto would be the "I think" easier of the two. But cost is going to be higher and its a more technical piece in an otherwise simple rig.



A good 4l80 should cost you 1200-2000 bucks, and the higher HP.tq rated performance units seem to be around 2800.00.. and thats before you look at what it takes to actually control it being its a computer controlled trans. Last time I looked it was just under a grand or so for the stand alone set up but someone had posted a much cheaper option I just cant recall the manufacture.

Or a gear venders unit might actually work out to be easier and cheaper.

Another option.. more or less a can of worms is to swap in a low mile 4l80e and a 6.0 motor from a newer truck:D then you need to add in the standalone harness rework, tune, fuel system, adaptor to the 205, motor mounts and trans mount..

Nice part is you would maybe see a bit better mpg, gain the overdrive, loose some weight, add fuel injection, better throttle response ..but you would be looking at a solid 2500-3500 for the swap and parts.

-shawn
 
If he wants to spend the money and time, I say go for it, but I am a little puzzled.

Being primarily a F*rd guy, I'm not up on the latest GM stuff.

But, other than not having an OD, the last I heard, a TH400 backed by a NP205 was pretty damn good.
If the tranny is still in good shape, why not fix the leaks?

Unless he's knocked a hole in it, how many places could it leak? Pan gasket, cooling lines, output shaft seal?
The worst would be a torque converter/input seal.

I would throw a few bucks into some seals and a complete transmission service, stop all the leaks, and then drive it while I did the necessary research to determine costs and problems to do a conversion.

Take my time, get all the parts lined up, get the necessary input from folks here who have already done it, and then go for it over a week or so.

Otherwise, you may be down a month or two getting everything right.

J.
 
700r4 wouldn't work well in this situation since it is behind a big block. It will not live a very long life with that much torque being pushed through it.
 
lectric80 said:
700r4 wouldn't work well in this situation since it is behind a big block. It will not live a very long life with that much torque being pushed through it.
Click to expand...

Really? i was going to use a 700R4 for my 400CI 6.6l and the shop i was talking to about it said it would handle it with ease? I woulda thought a 700R4 would handle it perfectly. Did you have a bad experience with the 700R4 behind a big block?
 
I plan to use a 700r4 behind my 383, but it will be a BTO stage 2 or 3 built to handle the torque. Most 700r4's will not live long because they are not designed for the torque of the big blocks. The 700r4 and later 4l60e were designed specifically for small block applications with much less torque. The larger th400 and 4l80e's were designed for the big block and diesel applications.

The other issue in this case would be the output of the 700r4 versus a 4l80e or th400, which is 700's use a 27 spline output, while the bigger transmissions use a 32 spline output. If he wants to keep his 205, and I don't know why he wouldn't, he would have to change the input on the 205 to the smaller spline count to use with a 700.

Finally, I have had bad experience with nearly all 700's. They are very finicky and can be damaged too easily with an improper adjustment of the TV cable. The 4l80e is entirely electronic so there is less chance of major failures because of something as simple as a cable. Right now I am in the process of rebuilding my TH350 in Krusty, and it appears very likely it is the first time it has ever been done. This means that an unknown amount of miles and 30 years have elapsed, while most 700's don't last more than about 150k before needing to be rebuilt. Some may have better luck, but in my experience the 700 is just not stout enough for what he wants here.
 
Fordum said:
I would throw a few bucks into some seals and a complete transmission service, stop all the leaks, and then drive it while I did the necessary research to determine costs and problems to do a conversion.

J.
Click to expand...

Thanks for all of the input. I like the idea of sealing the current trans as a short term, maybe long term, fix.

I'm not sure I would be committed to swapping the trans if it were not dumping fluid everywhere. I don't love driving it at hwy speed with the current set-up, but that is only necessary to get it to the trails/camping. Maybe a big trailer would solve that cheaper.

I haven't driven a standard shift for many years, and may consider that a good alternative.

Any other ideas?
 
you can get full man valve body for the 4l80 so no computer needed.

but still needs work .

and 4l80 is around 2" longer than th400 so drive shaft mods needed.

and the shift linkage wont work diffrent position and direction of movement. so custom shifter needed.


read this on 4l80 to 205 http://coloradok5.com/forums/showthread.php?t=166233&highlight=4l80+205
 
lectric80 said:
I plan to use a 700r4 behind my 383, but it will be a BTO stage 2 or 3 built to handle the torque. Most 700r4's will not live long because they are not designed for the torque of the big blocks. The 700r4 and later 4l60e were designed specifically for small block applications with much less torque. The larger th400 and 4l80e's were designed for the big block and diesel applications.

The other issue in this case would be the output of the 700r4 versus a 4l80e or th400, which is 700's use a 27 spline output, while the bigger transmissions use a 32 spline output. If he wants to keep his 205, and I don't know why he wouldn't, he would have to change the input on the 205 to the smaller spline count to use with a 700.

Finally, I have had bad experience with nearly all 700's. They are very finicky and can be damaged too easily with an improper adjustment of the TV cable. The 4l80e is entirely electronic so there is less chance of major failures because of something as simple as a cable. Right now I am in the process of rebuilding my TH350 in Krusty, and it appears very likely it is the first time it has ever been done. This means that an unknown amount of miles and 30 years have elapsed, while most 700's don't last more than about 150k before needing to be rebuilt. Some may have better luck, but in my experience the 700 is just not stout enough for what he wants here.
Click to expand...

Well thats dissapointing since i was planning to get one pretty soon. Guess ill look at some others. Guess we all learned somethin here :)
 
One thing to remember, is that the transmission did not leak when new, and did not do so for thousands and thousands of miles.
So it can be fixed.
Whatever transmission you are thinking about putting in its place may leak someday too.
So, a leak by its self is not a good reason to replace the whole transmission.

I can remember when GM announced that they were dropping the TH400. There were howls from all the off road guys, and a lot of the dealerships.
Sure enough, GM had to eat a lot of warranty repairs on the TH350s they tried to put behind the big blocks over the next few years.

So, you have a very stout designed transmission there.
The first thing to do is to get the oil off of it. I'm sure there are several guys here who will post ideas.
You need to get it fairly clean so you can see where the leaks are coming from, but I would not use a highpower pressure washer. It can tear things loose, and drive soapy water into places you don't want it.

I had a friend of mine climb under his with a big comforter/blanket. It had several holes and was going to be tossed anyway, so he just reached up and wrapped it all around the transmission.
Used it like a giant shop towel.
Worked, he was able to see where the leaks were.
I'm sure others will chime in, but the first thing you want to check on, is the hole in the bell housing between the transmission and the engine. If you are losing transmission fluid out there, you will have to drop it to find out where the leak is. If you have to go that far, you might want to re-evaluate the situation.

Otherwise, hopefully its a pan gasket and maybe a cooling line fitting.

J.
 
Fordum said:
So, a leak by its self is not a good reason to replace the whole transmission...

you have a very stout designed transmission...

Otherwise, hopefully its a pan gasket and maybe a cooling line fitting.

J.
Click to expand...

Great insight.

Not sure I would scrap it for the sole reason that it is leaking. If the cost of repairing the leak is high enough, I would consider investing in a different trans which may lower the rpm on the highway. It's not that bad, but it does scream at about 2700-3000 rpm going 65-70 mph.

I did replace a valve seat after driving back from moab. Maybe it was not related to excessive RPM, but a faulty rebuild. In either case, repairing the leak makes me think about the "best bang" for the buck.

What issues will I face if I swap to a manual trans? Clutch linkage? Peddals? Mating a 205 to the trans? Etc?
 
You are seriously asking the wrong guy about swapping. But fortunately you are in the right place to get answers. Its almost certain that someone here has done just about anything you are thinking about.
As for the rpms throwing a valve seat, I suppose its possible, but my truck runs right at 3K at 65.
And I regularly ran it 70+ for many many miles.

I put 300K plus on the original engine, probably most of it highway miles. The only reason I swapped it, was a head gasket going bad and I was afraid to do a head job on an engine with that many miles without doing a complete rebuild.

Oil pressure was 40 at idle measured on a good mech. gauge, compression was good on all cylinders except for the bad gasket, and it didn't use oil between changes.

I really hated to send it back as a core, would rather have just rebuilt it. But I needed the truck quicker than that so I went with a name brand rebuilt long block.

So, in my case, I can't say that the high rpms shortened the life of the engine.


But, then again, its a Ford.....
So you have to expect things like that.......<G>.

Had to throw that one in there.

J.
 
Im not sure about the TH400 tranny but on my 700R4 it was leaking 2qrts a night and it was caused by the detent cable (TV cable on the 700R4) it wasnt sealing and mating to the tranny case right had to make an oring among other things to get it seald right. So i would check the detent cable area, pan gasket, front oil seal, and were it mates with the transfer case. Along with the cooling line connections.
 
use a can of oven cleaner, spray everything down and spray it off with the slight pressure from a sprayer on the hose, i did this to mine when i had leaks and works great, either that or spend about the same amount of money per can on brake cleaner, but usually need more than one :crazy:

definately check around the filler tube area too, i just had a trans rebuilt about 3 years ago, and just recently found it to be leaking from there, couldn't really pinpoint where it was coming from until i had to pull the trans out from a catastrophic failure while PULLING A FORD :crazy: :doah: :D :p:

gaskets are notorius for leaking too, can be difficult to get them to seal right.

i can't remember right, but i'm pretty sure the th400's don't use a cable setup, i thought they were vacuum activated, damn it sucks getting old, i just had my dually not more than 6 months ago and cannot remember what it used, but don't remember a detent cable.
 
Correct, TH400's use a switch on the gas pedal to activate passing gear. They don't use a detent cable at all.
 
So here is the skinny...

The pan gasket is leaking, the rear trans seal is leaking inside the adaptor for the 205, and the oil cooler lines are crushed. A lot of fluid was coming out of the vent.

And, the transmission had clearly overheated.

I'm going to have the shop pull the pan and check for damage/metal chunks and then decide what to do.
 
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