TH 400 ,erratic reverse ?

G

gczarny

fast is cool !
Joined
Nov 13, 2005
Hi everybody ,my TH 400 started to act weird , MVB with trans brake , have very slow reverse engagement or no reverse at times at all , this will happen with trans shifted into reverse or in neutral with trans brake switch applied ,same thing !
In the morning when fluid is cold I may get slow reverse engagement bit it will always work but....... after it gets hot I usually have NO REVERSE , the only way to get it to go in reverse is to rev it up quite a bit and may have to continue to do this since it will not stay engaged , any ideas ?
...............fluid and filter has been changed with additive to clean up valve body , nothing major found in the trans pan at that time .......
Thanks
Greg
 
How well does the t-brake hold ? Direct (3rd) ? It sounds like the band may be worn but can also be direct.
AG.
 
turbobitt said:
How well does the t-brake hold ? Direct (3rd) ? It sounds like the band may be worn but can also be direct.
AG.
Click to expand...
Well , I took it for a ride to work today so partial highway driving ,out of my garage reverse goes in without a problem , got on it couple of times on the highway ....1,2,3 direct gears feel great , got to my work place ...no reverse ...tried T-brake in neutral , same ,tried T-brake up to my 4200 RPM current 2 stage settings couple of times , holds fine ?
Any more to try ?
Thanks
Greg
 
gczarny said:
Well , I took it for a ride to work today so partial highway driving ,out of my garage reverse goes in without a problem , got on it couple of times on the highway ....1,2,3 direct gears feel great , got to my work place ...no reverse ...tried T-brake in neutral , same ,tried T-brake up to my 4200 RPM current 2 stage settings couple of times , holds fine ?
Any more to try ?
Thanks
Greg
Click to expand...
Well reverse uses direct and low reverse band, T-brake uses direct, forward and low reverse band to hold. Considering it held on the T-brake I would say the ban and clutches are OK.

Does it require the t-brake button/solenoid to engage reverse ?

Problem sounds to possibly be elsewhere. You may just need to dig inside. Who's valve body is it ? Should see if it required a check ball. It is possible that the checkball is wearing the separator plate causing problems. Valve body bolt torque should be checked. Also seen many issues with bad factory case machining and most of the time overlooked when someone is doing a performance build and omitting the gaskets. The rough machine marks are OK when using the factory gaskets and low/modulated line pressure but create big leak paths with high fixed line pressure if not corrected.
AG.
 
turbobitt said:
Well reverse uses direct and low reverse band, T-brake uses direct, forward and low reverse band to hold. Considering it held on the T-brake I would say the ban and clutches are OK.

Does it require the t-brake button/solenoid to engage reverse ?

Problem sounds to possibly be elsewhere. You may just need to dig inside. Who's valve body is it ? Should see if it required a check ball. It is possible that the checkball is wearing the separator plate causing problems. Valve body bolt torque should be checked. Also seen many issues with bad factory case machining and most of the time overlooked when someone is doing a performance build and omitting the gaskets. The rough machine marks are OK when using the factory gaskets and low/modulated line pressure but create big leak paths with high fixed line pressure if not corrected.
AG.
Click to expand...
well , t-brake solenoid " on " does not help in anyway when this is happening ,however I noticed something ........... it seems to work in the morning when the fluid is cool but by the time I get to work I have no reverse .....on the other hand this happened 3 times now .....driving back from work home I pull in my garage and try reverse and it is there .......same driving distance and such .... the only difference ....on the way back home I have AC on so ....my engine /trans temps stay low .... under 200F ??????? what does this mean ? loosing line pressure when hot ? .....by the way , I have no idea what it is exactly in it ,bought it this way but I have been using / racing this trans for over 6 years and this just started ?
Thanks .
Greg
 
gczarny said:
well , t-brake solenoid " on " does not help in anyway when this is happening ,however I noticed something ........... it seems to work in the morning when the fluid is cool but by the time I get to work I have no reverse .....on the other hand this happened 3 times now .....driving back from work home I pull in my garage and try reverse and it is there .......same driving distance and such .... the only difference ....on the way back home I have AC on so ....my engine /trans temps stay low .... under 200F ??????? what does this mean ? loosing line pressure when hot ? .....by the way , I have no idea what it is exactly in it ,bought it this way but I have been using / racing this trans for over 6 years and this just started ?
Thanks .
Greg
Click to expand...
Could be just about anything. if its an internal leak than it makes sense that it gets worse when hot. Could also be valve body bolts loose. Time to start digging.
AG.
 
I wouldn't trust any of them. Those performance builds are just parts thrown at them without attention to detail. Plus they probably don't have converter feed modification to keep your thrust bearing intact. Where are you located? I'm sure there is a vendor close by.


Sent from my iPhone using Tapatalk
 
turbobitt said:
I wouldn't trust any of them. Those performance builds are just parts thrown at them without attention to detail. Plus they probably don't have converter feed modification to keep your thrust bearing intact. Where are you located? I'm sure there is a vendor close by.


Sent from my iPhone using Tapatalk
Click to expand...
Sarasota Florida ,moved here 4 years ago from Illinois ( Jimmys trans ..... http://jimmys-trans.com/ ) was my guy up there but here I am " new guy " !
 
If your mechanically inclined I would make an attempt at it and rebuild it yourself. If you get stuck there are enough people on the board to help. Chris (CK performance) just released a good manual and makes and supplies a lot of TH400 stuff. This way you get a trans that's more tailored to you needs. You can take the money you saved from buying that Jegs transmission and put it towards some good hard parts if it doesn't already have them.
If you do a search there was a decent TH400 build thread a while back.


Sent from my iPhone using Tapatalk
 
I have to agree. If you can pull it out and get it back in, an overhaul isn't any harder than that. Buy the ck manual and order some parts and get a five gallon bucket to set the trans in tail down to drain out the fluid. Take a lot of pix as you disassemble as it might(probably does) have some non stock mods for the trans brake.
 
hi greg, before pulling trans out I would throw 0-300 psi guage on pressure port left side of trans. first check cold and then hot might even drive around a bit I usually tape guage to wind shield so you can moniter without holding guage. reason its working pulling out of garage is fluid is cold and thick ie higher pressure as it warms up fluid thins out. reverse pressure should be about 100 to 150 psi at 1000 rpm with shifter in rev. and foot on brake. also check in drive pressure should be about 60psi to 90 psi again with foot on brake 1000 rpm. this test will at least give you an idea if you have hydrsaulic leak in one of the circuits. if pressure is low in both rev. and drive pullpan and check for loose valve body bolts if reverse pressure is low only in rev.pull rear servo cover [big round cover at right rear of trans.] pull servo out and check seals,if nothing either band is going away or direct cluthes. hope this helps.
 
by the way forgot to mention always check trans. fluid if low rev. is first to be affected. turbo bitt hit nail on the head jegs and most of these places sell junk Ive built quite a bit of performance trannys for guys in my area and torn down quite a bit from these big outlets and its amazing what ive found
 
gunzandgearz said:
hi greg, before pulling trans out I would throw 0-300 psi guage on pressure port left side of trans. first check cold and then hot might even drive around a bit I usually tape guage to wind shield so you can moniter without holding guage. reason its working pulling out of garage is fluid is cold and thick ie higher pressure as it warms up fluid thins out. reverse pressure should be about 100 to 150 psi at 1000 rpm with shifter in rev. and foot on brake. also check in drive pressure should be about 60psi to 90 psi again with foot on brake 1000 rpm. this test will at least give you an idea if you have hydrsaulic leak in one of the circuits. if pressure is low in both rev. and drive pullpan and check for loose valve body bolts if reverse pressure is low only in rev.pull rear servo cover [big round cover at right rear of trans.] pull servo out and check seals,if nothing either band is going away or direct cluthes. hope this helps.
Click to expand...
This is a trans brake VB so most likely fixed line pressure. I would expect to see anywhere between 160-220 PSI in all gears depending on pressure regulator set-up and springs. would still check it at high idle or maybe even 1500 RPM. Direct drum will have a bleed hole drilled in it and will create a noticeable pressure drop at low RPM and idle.
AG.
 
yeah that's right I was a little low on pressures those are factory pressures not for mvb. I would still pressure test to see if pressures change in rev compared to the forward gears. still sounds like clutches or band to me because its working when fluid is cold more pressure behind clutch or band goes away when hot.any way just trying to help.
 
Thanks everybody ,I will try to get the line pressure tested per your suggestions ,it may take few days but I will post back when I know the details .Thanks again .
Greg
 
You must log in or register to reply here.

Similar threads

T
200r4 KC VB governor modifications
Replies
19
Views
2K
77 cruiser
7
TIMINATOR
TURBO T LIMITED SHIFT LINKAGE
Replies
10
Views
952
TIMINATOR
TIMINATOR
VADR
Losing Power at WOT - No Codes
2
Replies
25
Views
2K
John Larkin
John Larkin
HalfDozIN
PTC converter ID
Replies
1
Views
1K
SCOOBY DOO
SCOOBY DOO
C
GN dead on the 1-2 shift
Replies
11
Views
992
TIMINATOR
TIMINATOR
Top