TH400 Help - Hot Rod Forum : Hotrodders Bulletin Board
Hotrodders.com -- Hot Rod Forum



Register FAQ Search Today's Posts Unanswered Posts Auto Escrow Insurance Auto Loans
Hot Rod Forum : Hotrodders Bulletin Board > Tech Help> Transmission - Rearend
User Name
Password
lost password?   |   register now

Reply
 
LinkBack Thread Tools
  #1 (permalink)  
Old 11-03-2003, 02:29 PM
Registered User
 
Join Date: Nov 2003
Location: Buffalo, MN
Posts: 8
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
TH400 Help

Hello,
I am fairly new to tranny, but not engine work. I searched through posts and knowledge base but nothing directly related to my problem.
I have a 90 suburban 2500 4X4 that had a rebuilt tranny one year ago. I bought it with a cracked flexplate.

The th400 took a dump on me on the highway first slipping, then heating up. I checked fluid and it came up way over full. I believe the pump gave out.
I have had this tranny down but not out 3 times now and Im gonna give up soon.
I replaced the flywheel, TC with reman, and then the pump central drive - because the tangs were broken.
When I put the flywheel in with the new TC I noticed there was a huge gap between the TC and flywheel like over 1/2 inch or so. When I replaced the pump I spaced out the gap with washers.

Now - I have very little pressure in the lines, I shot them out with air, and replaced the filter, cleaned off all I could get to.

Now I can get the truck to move at about 2K or so of revving. If I give it more gas, it reacts as a stall converter and slams into gear. I also have a mean shudder going.
I dont know if I should look to the pump again, I just replaced the inner drive gear, into my pump. I did clean out the pressure reg.

BTW after the initial failure there was very little metal in the pan, alot of sludge. The fluid was burned initially

I just dont know where to go with it. How can there be little pressure with a pump that should work? Unless I put something in wrong.
I appologize that this post is so long but I wanted to cover all the bases.
Thanks in advance for your help.

    Advertisement
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
  #2 (permalink)  
Old 11-03-2003, 03:30 PM
New Member
 
Join Date: Oct 2003
Location: Rockledge Fl
Posts: 19
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
The sludge that was in the pan is one of the problems. Due to the low line pressure from the broken pump, the clutches have burned (which is causing the shuddering problem). This clutch material has moved to the valve body and is most likely causing valves to stick, causing more problems. When you replaced the pump, did you surface the stator side, or just replace the gears? The next issue that I would look at is the spacing between the flexplate and the converter. When you align the converter correctly into the pump and onto the input shaft, there should be a gap between the pads of the converter and the flexplate. This gap should be 1/8 to 3/16 of an inch. You should have to pull the converter bnack out this distance to bolt it up to the flexplate. Over 3/16 of an inch and there will not be enogh engagment with the pump and the gears will fail. Under 1/8 and the converter will be engaged too far into the pump and the gears will wear into the stator side and loose pressure.

I hope that this helps.
Reply With Quote Quick reply to this message
  #3 (permalink)  
Old 11-03-2003, 03:32 PM
BstMech's Avatar
NYOFP4RJ3CHRIS
 
Join Date: Sep 2002
Location: TN. In the corporate states of America
Age: 41
Posts: 1,552
Wiki Edits: 0

Thanks: 0
Thanked 1 Time in 1 Post
Re: TH400 Help

Quote:
Originally posted by droptop50
there was very little metal in the pan, alot of sludge. The fluid was burned initially
That sludge is clutch dust, the dust is caused from the friction material being burned off from the clutch discs. Lot's of heat is caused from the clutches slipping. The more you try to drive it, the more costly repairs are going to be.

You should never space the converter away from the flywheel. The pilot hub needs to be centered in the rear of the crank, or you can cause premature bushing wear in the pump, as well as crack the flexplate among other things.

Sounds like rebuild time and I would carefully inspect things to see what caused it to go out again in such a short time. Maybe just driving habits or heavy towing?
Reply With Quote Quick reply to this message
  #4 (permalink)  
Old 11-03-2003, 03:46 PM
Registered User
 
Join Date: Nov 2003
Location: Buffalo, MN
Posts: 8
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Thanks for your help on this.
The flexplate wasnt replaced on the first rebuild. This is what lead to problems to begin with it cracked in a circle around the crank bolts.
I thought the TC was to be seated the full 3 clicks onto the shaft. This left me with the 1/2 inch gap or so.

Should I attempt to take out the washers so the TC comes back out a bit? I assume there should be no washers between the TC and the flexplate. How do I know it hasent come off the drive tangs of the pump?

With the gap specifiations - you do mean between the flywheel and TC? What do I put in the gap? nothing? I am confused, again. How do you tighten the flywheel to the TC if there is a gap between them?

And no I didnt resurface the stator side. I just replaced the gears. I havent driven this at all, its just been sitting.

I was worried that the first time I had this out that the TC wanst seated all the way - and thats what wrecked the tangs. This is what made me use the washers to space it out.

Last edited by droptop50; 11-03-2003 at 03:55 PM.
Reply With Quote Quick reply to this message
  #5 (permalink)  
Old 11-04-2003, 01:39 PM
club327's Avatar
Member
 
Last photo:
Join Date: Nov 2003
Location: australia
Age: 49
Posts: 334
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Check the pressure regulator valve. Sounds like uv'e done as much as any mortal can do. There should always be some freeplay between the f/plate and the torque convertor, but not half inch. Usually about 1/8 to a 1/4 is what's expected. So the tran's is slipping. Does it also slip when held manually in the lower gears? Does it also slip in reverse? It would be unlikely that all the clutch plates and bands have burnt out. Like I said, try the p/regulator valve. You should have decent line pressure and it's very rare for a pump to be at fault. The only fault pumps tend to give is a whirring noise when there's something wrong there. I hope you can solve this one
Reply With Quote Quick reply to this message
  #6 (permalink)  
Old 11-05-2003, 09:51 AM
Registered User
 
Join Date: Nov 2003
Location: Buffalo, MN
Posts: 8
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Ok,
I have finally dedicated a day to take a look at this again.
I measured the gap that the washers are taking up and its exactly a 1/4 inch. So I can assume that by putting these in here I may have damaged the pump.

I will take them out and see what happens. Then if the same I will have to remove the pump AGAIN.

I thought the distance was greater than that. Hopefully by not running it much - starting and moving it in the driveway I havent damaged it too bad YET. We will see.

Any input would be appretiated.
Reply With Quote Quick reply to this message
  #7 (permalink)  
Old 11-05-2003, 12:58 PM
Registered User
 
Join Date: Nov 2003
Location: Buffalo, MN
Posts: 8
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Well, after removing the washers, I now get movement of the vehicle with litte revving. Its still seems a bit not to grab or Bite right away. I put a new vac mod in it - maybe I should look to adjust that.
The symptoms are in all gears - and all the same.
Thanks
Tim
Reply With Quote Quick reply to this message
  #8 (permalink)  
Old 11-08-2003, 02:47 PM
Registered User
 
Join Date: Nov 2003
Location: Buffalo, MN
Posts: 8
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Update:
For those that are learning like me. The pump gear did grind itself into the stator side pump housing. I will up load a pic later.
Luckily the gear still measures out.
DONT EVER SPACE OUT YOUR TC FROM FLEXPLATE.. I shouldnt have listened to some *******.
Reply With Quote Quick reply to this message
  #9 (permalink)  
Old 11-08-2003, 06:59 PM
krp's Avatar
krp krp is offline
New Member
 
Join Date: Nov 2003
Location: Regina SK. Canada
Posts: 16
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Sounds to me like your pump support is cut in from your pump gear. With any more than .002 or at most .003" side gear clearance your pump efficiency is going to drastically decline. The sludge may be caused by some clutch material, true enough, but my guess is a lot of it is from the material ground off your pump support. You need to get the unit out of the vehicle and replace the support. With that much metal you might be wise to freshen up the whole unit or you could be looking at stuck valves in the valve body and or govenor which is going to give you more grief.

Oh, and btw, the reason you have so much convertor to flexplate clearance is because your pump gear moves back into the cover where it has been machined out. Absoluet max. clearance from convertor mount pad to flexplate mount pad is 1/4'' with less prefered.

One more thing. With a stack up of tolerence it is possible to have too much clearance between the pads of the convertor and the flexplate. It is acceptable to shim the converter slightly if you run into this stack up, BUT, all shims have to be EXACTLY the same thickness, and no more than .100 to .125" max. If you need more, you've got other problems.
Reply With Quote Quick reply to this message
  #10 (permalink)  
Old 11-09-2003, 10:57 AM
Registered User
 
Join Date: Nov 2003
Location: Buffalo, MN
Posts: 8
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
I dont want to realize it - but im sure the clutches or something are gone.

I got this all back in - pump pressure is good. Replaced pump housing got fluid levels back and now:
I have a hard reverse
Gotta rev to get movement in any drive gear, kinda floaty, if given too much gas its a hard grab - then no shift out of first at all.

Seems when the time comes to shift into second the trans makes a funky noise like something heavy being slid across a concrete floor - kinda like a beaten dog!

I dont know and Im getting frustrated. I didnt expect much to begin with but the damn thing should just bust or work not this in between stuff.

Could this be the governer? These symptoms are the same in all forward gears.
Reply With Quote Quick reply to this message
  #11 (permalink)  
Old 11-09-2003, 12:37 PM
krp's Avatar
krp krp is offline
New Member
 
Join Date: Nov 2003
Location: Regina SK. Canada
Posts: 16
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
I hate to be the bearer of bad news, but I think you already realize there is some kind of internal problem. I don't know what the noise is that you hear. What I would like to ask you is when you changed the pump cover/stator support, did you put the sealing rings on it? Were they teflon or metal rings? Any trouble installing it into the case? Those two rings supply the sealing for the forward clutch drum. If missing(probably wouldn't move at all) or damaged, creating a leak, it's possible that could be your engagement into drive problem. Your harsh reverse could be a stuck PR valve, or modulator valve causing hi line. The no upshift could also be stuck modulator, govenor or even shift valves from the metal in this unit. You are going to have to remove, disassemble and thoroughly clean and inspect this unit. Make sure no more damage has ocurred to the clutches and hardparts, and check all valves for cleanliness and free movement. Good luck.
Reply With Quote Quick reply to this message
  #12 (permalink)  
Old 11-11-2003, 05:16 PM
Registered User
 
Join Date: Nov 2003
Location: Buffalo, MN
Posts: 8
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Thanks for your help. They were metal rings on the pump. I put in a new vac mod, I havent checked the Governer yet.
As of right now it still does the same thing. Just doesnt "grab" right away. You really dont have to race it. Just a small amount of gas and it grabs - it doesnt slip out of gear.
If on an incline in any forward drive you roll back until given gas.

I will look to completely dissasemble it, unless someone can think of anything else.
Thanks Again
Reply With Quote Quick reply to this message

Recent Transmission - Rearend posts with photos

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the Hot Rod Forum : Hotrodders Bulletin Board forums, you must first register.
Please enter your desired user name (usually not your first and last name), your email address and other required details in the form below.
User Name:
If you do not want to register, fill this field only and the name will be used as user name for your post.
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.




Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools

Posting Rules
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On



All times are GMT -6. The time now is 05:29 PM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0 PL2
Copyright Hotrodders.com 1999 - 2012. All Rights Reserved.