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So I rebuilt my 1st engine (Olds 455) AND transmission (th400). The engine is running fine, but today is the first time I've shifted it out of park (procrastinated in fear of my transmission rebuild being unsuccessful). I have my '64 on jack stands with no rear wheels in these situations. I am using Slick Shift oil in the tranny.
I have two problems:
1. If I shift into Reverse and leave it in reverse the engine dies.
2. Shifting into Drive works, but once I bring the RPMs up over 2000 the axles immediately stop causing the engine to stall.
What is most likely screwed up?
***Because I feared this I did buy a backup th400 that does work.
Is this a stock rebuild? If not, what was done during the overhaul?
Make sure the sealing rings on the rear servo and accumulator piston are in good shape. Missing or misplaced check ball, valve body gaskets mispositioned or mismatched? Pressure regulator assembled incorrectly?
Need more info to help you troubleshoot on the net.
Basics first:
Fluid level and condition?
Pull the driveshaft and see if the problem goes away. If yes it's in the rear end...drums/brakes binding.
No, unbolt the converter and push it back into the trans and run the engine. Run ok? Yes... then its the trans.
What condition was the trans in before the rebuild?
Was the rebuild environment clean?
Did you fill the converter and properly seat it into the pump?
Did you presoak the frictions in trans fluid prior to assembly?
Did you replace all the bearings or no?
Did you struggle with any portion of the rebuild process?
Did you pull the valve body apart clean inspect and reassemble properly?
Any leftover parts?
Many things can go wrong being a first-timer. Its easy to roll or damage a seal which will cause a cross leak or not allow pressure to build.
The easiest way to test a transmissions health is by checking its blood pressure
We will need proper pressure readings in PRNDLSL to help you.
What kind of rebuild kit did you use? Was the band installed right?
Did the clutch pack stacks meet spec against the retainer snap ring?
Did you actuate things with compressed air as a bench test?
Shift kit?
Thank you for taking your time to helping me! I really enjoyed tearing down and building this transmission. I truly hope I can figure out and fix the problem as I'd love to be able to say that I rebuilt the trans in my pickup.
I know I won't be able to answer with the detail you probably need, but I'll do my best.
Would installing the 34 element sprag backwards cause this? I've had a couple of guys say this might be the cause.
Originally Posted by matt69olds
Is this a stock rebuild? If not, what was done during the overhaul? Yes, this was a stock rebuild other than a Transgo shift kit and upgraded to a 34 element sprag.
Make sure the sealing rings on the rear servo and accumulator piston are in good shape. Missing or misplaced check ball, valve body gaskets mispositioned or mismatched? Pressure regulator assembled incorrectly? I will be pulling the transmission and replacing it with the spare then opening this one up. I used a th400 rebuild manual and used YouTube videos and believe I installed everything correctly.
Do you have access to a line pressure gauge?
I don't have one. Can I rent one?
Originally Posted by droldsmorland
Need more info to help you troubleshoot on the net.
Basics first:
Fluid level and condition? All new fluid and the dipstick showed fine while in neutral.
Pull the driveshaft and see if the problem goes away. If yes it's in the rear end...drums/brakes binding.
No, unbolt the converter and push it back into the trans and run the engine. Run ok? Yes... then its the trans. I will be checking this over the weekend.
What condition was the trans in before the rebuild? Fluid looked and smelled good. It probably did not need anything done to it.
Was the rebuild environment clean? It probably could have been better, but it wasn't bad.
Did you fill the converter and properly seat it into the pump? Yes and yes.
Did you presoak the frictions in trans fluid prior to assembly? Yep.
Did you replace all the bearings or no? Replaced them all.
Did you struggle with any portion of the rebuild process? Only problem was the damn lip seals. I tore one then bought 5 more just in case. Once I got the hang of it they went in fine.
Did you pull the valve body apart clean inspect and reassemble properly? This is the most likely place of error. One guy on an Oldsmobile Facebook page said it sounds like the manual valve is messed up or there is a crack in the VB. I do have an extra in good condition that I will swap in.
Any leftover parts? Ha! No, thank goodness!
Many things can go wrong being a first-timer. Its easy to roll or damage a seal which will cause a cross leak or not allow pressure to build.
The easiest way to test a transmissions health is by checking its blood pressure
We will need proper pressure readings in PRNDLSL to help you.
What kind of rebuild kit did you use? Was the band installed right? I bought one off of ebay with green alto frictions. It had very good reviews.
Did the clutch pack stacks meet spec against the retainer snap ring? Using the feeler gauges I had they did.
Did you actuate things with compressed air as a bench test? I did and they worked like a couple of YouTube videos demonstrated.
Shift kit? Yep. Transgo.
Originally Posted by matt69olds
Another question, how is the tune of the engine? It runs fine, but I know it needs more tuning. I think I have a small vacuum leak. Haven't tried to find it yet.
Is the converter new or rebuilt? It was a barely used converter with a stall around 2400 rpms. Bought off from a member on this site.
Did you air test the clutch packs during overhaul? Yep, and all appeared to be working ok.
any oil pressure gauge that will read to at least 250-300 psi will work. The line pressure rap is the 1/8 pipe plug right above the shifter linkage. If your rubber tip on your blow gun won’t fit, use a short peice of 3/16 brake line. Wrap the end with several layers of electrical tape. Then you can bend the line and apply and remove whatever you need to make it fit into the hard to reach holes apply holes.
did you completely disassemble the valve body for cleaning? Did you have a book or diagram to show how the springs and valves go back together? Did all the valves move freely, and snap back under spring tension? If the clutches air tested ok on the bench, and you didn’t break or cut a sealing ring during assembly, your problem is most likely in the valve body. Did you use the valve body gaskets that came with the shift kit, and not the ones included with the overhaul kit? The shift kit requires the shift kit gaskets, stock won’t work.
Did you use iron rings or Teflon? It’s pretty easy to cut Teflon rings and not notice it setting the drum in place. You would really have to get rough to break the iron rings.
id get an exploded view of the valve body, and lots of break clean. Remove each valve,bushings, springs, sleeves, whatever, one at a time, and take detailed notes on how and in what order things came out. There are some different calibrations and design changes made over the years, so the diagram may not match your particular valve body exactly. Throughly clean the bore, a gun cleaning brush works well. Brake clean everything, then reassemble each valvetrain. Make sure the valves move freely before moving on the the next.
If the trans has to come back out, there are much easier and cheaper ways to firm up shifts besides spending money on a shift kit.
Ya, I agree Matt sounds like a cross leak or a separator plate isn't right on the worms.
jpayne do the pressure test before diving into it. A decent high-pressure gauge set won't break the bank.
It will help to narrow in on the problem circuit.
My hunch is you did something wrong in the trans and you have 1st and 2nd gears engaging at the same time locking the output shaft.
if first and second gear are applied at the same time, you have second gear. If you look at a gear range chart, 1st gear has the forward clutch applied, and the low roller clutch holding. To get second gear, the intermediate clutch is added. Third gear has everything for first and second still applied, then the direct clutch is added.
For reverse gear, the direct clutch becomes the diving clutch. The reverse band is applied, and the low roller clutch free wheels backwards. This is a very brief description of how the various gears are achieved. The reverse band is also applied in manual low to provide engine braking, the intermediate band provides engine braking in manual second gear.
For the output shaft to lock up, there needs to be a forward gear applied, and reverse at he same time. This is basically how a transbrake works. The most likely place for fluid to cross leak is the rear servo. The large piston under the servo cover applies the reverse band. The smaller inner piston is the accumulator for 2nd gear. If reverse fluid leaks around the large piston, it can cross leak into the second clutch passage, causing a bind up.
The TransGo shift kit adds another potential crossleak area. There are 2 hydraulic chambers in the direct clutch. One is for 3rd gear, the other is reverse. The TransGo plate allows the application of both hydraulic chambers to be used in on 3rd gear, basically tripling the piston apply area on the clutches. To do that, the spacer plate has to cover a couple holes, and re-route 3rd gear oil. Using stock gaskets with the TransGo spacer plate is a potential leak. Same thing with swapping the upper and lower gaskets.
if first and second gear are applied at the same time, you have second gear. If you look at a gear range chart, 1st gear has the forward clutch applied, and the low roller clutch holding. To get second gear, the intermediate clutch is added. Third gear has everything for first and second still applied, then the direct clutch is added.
For reverse gear, the direct clutch becomes the diving clutch. The reverse band is applied, and the low roller clutch free wheels backwards. This is a very brief description of how the various gears are achieved. The reverse band is also applied in manual low to provide engine braking, the intermediate band provides engine braking in manual second gear.
For the output shaft to lock up, there needs to be a forward gear applied, and reverse at he same time. This is basically how a transbrake works. The most likely place for fluid to cross leak is the rear servo. The large piston under the servo cover applies the reverse band. The smaller inner piston is the accumulator for 2nd gear. If reverse fluid leaks around the large piston, it can cross leak into the second clutch passage, causing a bind up.
The TransGo shift kit adds another potential crossleak area. There are 2 hydraulic chambers in the direct clutch. One is for 3rd gear, the other is reverse. The TransGo plate allows the application of both hydraulic chambers to be used in on 3rd gear, basically tripling the piston apply area on the clutches. To do that, the spacer plate has to cover a couple holes, and re-route 3rd gear oil. Using stock gaskets with the TransGo spacer plate is a potential leak. Same thing with swapping the upper and lower gaskets.
Great info! Thanks!
So, according to this diagram, should I be looking at
numbers 70 and 71 for damage?
Hats off Matt great explanation of the order of operation!
Root cause analysis is your friend if used properly.
jpayne I'm suggesting to start with simple troubleshooting techniques working towards systematic disassembly with basic pressure readings before its gets ripped out of the car.
In other words, don't rip into it until you see what's out of spec. You will possibly lose that root cause if you disassemble without baseline readings.
This can lead to tail chasing, a string of cuss words that make zero grammatical sense, hair loss, vaporizing money and missing tools due to being flung towards the floor at terminal velocity.
Wouldnt the gauge test show the "bad" circuit(s)..if the engine doesn't stall. He would see the excessive line PSI in D from idle to 2K where it locks up.
Id like to see PRNDSL pressure readings at idle and at 1000 and then at 2000 in D.
I have not installed a trans brake in 35 years and I can't remember what those readings would be off idle up to the controlled release RPMs.
The fact that it's doing this on its own points to a cross leak (you are on to it likely with the apply piston seals). Something is applying with increased line pressure. So it is not a large leak...yet
Another thought is to give TransGo tech a call. TCI has instant chat and a great tech line as well. They will want pressure readings.
What would max line pressure be in a th400? I want to make sure I get a gauge that will go high enough.
Originally Posted by droldsmorland
Hats off Matt great explanation of the order of operation!
Root cause analysis is your friend if used properly.
jpayne I'm suggesting to start with simple troubleshooting techniques working towards systematic disassembly with basic pressure readings before its gets ripped out of the car.
In other words, don't rip into it until you see what's out of spec. You will possibly lose that root cause if you disassemble without baseline readings.
This can lead to tail chasing, a string of cuss words that make zero grammatical sense, hair loss, vaporizing money and missing tools due to being flung towards the floor at terminal velocity.
Wouldnt the gauge test show the "bad" circuit(s)..if the engine doesn't stall. He would see the excessive line PSI in D from idle to 2K where it locks up.
Id like to see PRNDSL pressure readings at idle and at 1000 and then at 2000 in D.
I have not installed a trans brake in 35 years and I can't remember what those readings would be off idle up to the controlled release RPMs.
The fact that it's doing this on its own points to a cross leak (you are on to it likely with the apply piston seals). Something is applying with increased line pressure. So it is not a large leak...yet
Another thought is to give TransGo tech a call. TCI has instant chat and a great tech line as well. They will want pressure readings.
Needs to be an HD gauge with matching High(er) psi hose with a max of 300psi or more. Should come as a kit with a nipple assortment. Keep in mind this chart is for a stock TH400 trans and a stock converter. Note some of these are loaded pressure specs, brakes on and up on the converter.
Needs to be an HD gauge with matching High(er) psi hose with a max of 300psi or more. Should come as a kit with a nipple assortment. Keep in mind this chart is for a stock TH400 trans and a stock converter. Note some of these are loaded pressure specs, brakes on and up on the converter.
Most manual valves bodies and transbrake have fixed line pressure, meaning the only thing that controls line pressure is the pressure regulator valve. The typical stock blue regulator spring with 2 horse shoe shims will usually produce around 180ish psi, which is plenty for 700-800 hp. Most aftermarket springs bump the pressure up to around 200-220. You don’t want to run much more than that, the lugs in the case that retain the intermediate clutches can tear out of the case. The thick snap ring that TransGo includes with the shift kit helps with that, but its only a crutch. When the lugs break, it tears up the direct drum and center support.
Line pressure can go to about 250-280 in reverse under heavy throttle. If you have ever noticed the loop bent into the metal modulator line and wondered why it’s there, it’s to prevent condensation that might form in the steel line from draining into the modulator. If enough collects there and freezes, it can lock the modulator valve in place. Start the engine, fast idle, shift the trans into reverse, with the modulator valve locked line pressure is uncontrolled. It will most likely break the rear band, servo piston, shatter the direct clutch piston or drum. Those in readerland who have read some of my long winded transmission lectures might recall that the 4L80 trans is basically a 400 with a overdrive clutch in front of the normal 400 internals. The early 4L80 were well know for worn boost valves, resulting in the same potential damage. Luckily, in a cost cutting move, Hydromatic also made the pistons and servos a little thinner/weaker. Those usually break first, saving the more expensive parts.
Last edited by matt69olds; January 11th, 2020 at 07:37 PM.
My hunch is you did something wrong in the trans and you have 1st and 2nd gears engaging at the same time locking the output shaft.
if first and second gear are applied at the same time, you have second gear. If you look at a gear range chart, 1st gear has the forward clutch applied, and the low roller clutch holding. To get second gear, the intermediate clutch is added. Third gear has everything for first and second still applied, then the direct clutch is added.
For reverse gear, the direct clutch becomes the diving clutch. The reverse band is applied, and the low roller clutch free wheels backwards. This is a very brief description of how the various gears are achieved. The reverse band is also applied in manual low to provide engine braking, the intermediate band provides engine braking in manual second gear.
For the output shaft to lock up, there needs to be a forward gear applied, and reverse at he same time. This is basically how a transbrake works. The most likely place for fluid to cross leak is the rear servo. The large piston under the servo cover applies the reverse band. The smaller inner piston is the accumulator for 2nd gear. If reverse fluid leaks around the large piston, it can cross leak into the second clutch passage, causing a bind up.
The TransGo shift kit adds another potential crossleak area. There are 2 hydraulic chambers in the direct clutch. One is for 3rd gear, the other is reverse. The TransGo plate allows the application of both hydraulic chambers to be used in on 3rd gear, basically tripling the piston apply area on the clutches. To do that, the spacer plate has to cover a couple holes, and re-route 3rd gear oil. Using stock gaskets with the TransGo spacer plate is a potential leak. Same thing with swapping the upper and lower gaskets.
I was just kinda spitballing and hoping someone with good trans knowledge would pipe in. I wasn't sure if it would happen with two different forward gears engaged or not, but I didn't understand how the reverse clutch would get engaged while moving forward. Now I do.
I just purchased a transmission pressure gauge (300psi hose and gauge goes to 300 psi) online. I'll let you know what the pressures are for each gear when I get the gauge.
While waiting for the transmission gauge and since I already have my truck on jack stands, I decided to drop the pan to look at the rear servo. I don't see anything wrong with it. Should I replace the metal seals on the small piston with rubber seals?
Here is a picture of the parts:
***Could this be a problem from the rebuild: I did the dual feed direct clutch mod (removing lip seal in direct drum, leaving out second sealing ring in the center support, and block reverse passage with plug in the case) AND used the TransGo separator plate at the same time?
Last edited by jpayne_80@hotmail.com; January 12th, 2020 at 06:07 PM.
If you left the 2nd sealing ring off the center support, and left the center seal out of the drum, get rid of the TransGo plate. Get a 7/16 freeze plug (Dorman number 555-003) and drive it into the round hole on the drivers side of the center support bolt. I’ll take a pic tomorrow of a separator plate and show what holes to drill.
This is the check ball location I use for all my race or performance builds. You can use the same check ball locations outlined in the TransGo instructions if you prefer. These 2checkballs are the absolute minimum required for a automatic shifting build. Drill these 2 holes in your original spacer plate. Or you can follow the TransGo instructions if you prefer. If your using a stock or mild converter, drilling them to 3/16 will definitely produce a firm shift.
Lastly, remove the spring in the 2-3 accumulator. Tap the small round feed hole for a 1/4x1/4 set screw (I think that’s the correct size). Reinstall the piston without the spring, then install the setscrew. The spring was omitted on most heavy duty truck and all the W-30, Stage One Buick, Ram Air Pontiac performance cars. The TransGo shift kit plate restricts the feed hole to the accumulator, it’s the hole the describe in the instructions as accumulator feed. Obviously you can’t make the existing hole in the stock plate smaller, the setscrew does the same thing as making the feed hole smaller.
Other than replacing some of the thrust washers with bearings, this is the basic calibration and tips I use for most of my performance builds. I have many friend with 400 behind LS engines with well over 1000hp, other than the forward clutch hub the stock parts are pretty reliable up to about 1200. After that, it’s time to consider an aluminum direct drum and more clutches in each drum.
Hoping to get out to the shop to reinstall the valve body, pan, and oil and fire it up tonight. Between illness and cold weather I haven't had a chance to get out there. I do have an oil pressure gauge now so I'll record and post the results in each gear.
Good news, Fellas! I believe I got the transmission functioning properly. There were several places in the valve body that had some rust making a couple of the valves tough to move. I ended up using a different valve body I had. It was rust free but I removed everything and cleaned it really good anyway. Once I put it all back together and added oil, the transmission would go in reverse and not lock up. All other gears worked, too. I'm excited to get it on the ground to test it. Hopefully that goes without a hitch (with my luck there will be multiple hitches).
As for the oil pressure, each gear seemed to be in the proper range. The only question I have is should the pressure have dropped when I would rev the engine for a second or so?
I was not able to get the best oil pressure readings as my truck kept popping a fuse, shutting down the engine. Apparently I misread needing an 80 amp fuse (with larger) wire for a fuse rated at 30 amps. When I hooked up my two Viair compressors for air ride a 30 amp fuse was nowhere near enough, popping the small fuse. Doh!
I truly appreciate all of your advice!
Last edited by jpayne_80@hotmail.com; January 31st, 2020 at 04:11 PM.
Pressure should go up until the regulator hits its open limit...not down. Are you reading the PSI hot or not?
Not hot.
I failed to mention that I have a vacuum leak at carb/intake which causes my truck to idle around 2000 rpms. Getting ready to pull intake manifold anyway. Not sure if this will make a difference.
I have a vacuum leak at carb/intake which causes my truck to idle around 2000 rpms. Getting ready to pull intake manifold anyway. Not sure if this will make a difference.
Fix the engine first. When the engine runs right, maybe the trans will work OK.
There's nothing in the trans that can lock up and stall the engine...because the engine should be able to idle with the torque converter slipping. It does that at every stop-light.
I assume you put a freeze plug in the case to block reverse feed?
The stock plate drilled, with the reverse feed blocked is a much better setup than the TransGo plate. The TransGo kit is a ok setup if you don’t have the trans out for overhaul.
I assume you put a freeze plug in the case to block reverse feed?
The stock plate drilled, with the reverse feed blocked is a much better setup than the TransGo plate. The TransGo kit is a ok setup if you don’t have the trans out for overhaul.
January 7th, 2020, 05:13 PM
Once I got the hang of it they went in fine.
