poor fitting sun tube to direct drum
Thread Starter
Joined: Nov 2013
Posts: 6,389
Likes: 558
From: Portlandia
poor fitting sun tube to direct drum this is a fellow racer i met at the track last night who lost third. I figured he did a 1-2 burnout and rolled the sprag. pull it apart and everything looks decent. the CS bushing was flaking apart which is odd.
anyways i took this video to show the shitty fitment of the sun tube splines into the direct. even a stock drum is nicer fitting.
is this BTE drum supposed to be used with a different sun tube?
other details: stock case, JW bell, TCI Iron RVMB brake, billet fwd hub. tolerance were in the ballpark for endplay and such. nothing special but nothing terrifying.
anyways i took this video to show the shitty fitment of the sun tube splines into the direct. even a stock drum is nicer fitting.
is this BTE drum supposed to be used with a different sun tube?
other details: stock case, JW bell, TCI Iron RVMB brake, billet fwd hub. tolerance were in the ballpark for endplay and such. nothing special but nothing terrifying.
Teching In
Joined: Aug 2021
Posts: 29
Likes: 7
The intermediate sprag comes on in second gear, not third. The direct clutch comes on in third. How did the clutches look? How did the direct drum air check?
FYI, I see there's scarf cut rings on the CS. Air checking the direct drum can be difficult with those rings. You may have to add some ATF to the lube hole in order to get them to air check.
I'd change the CS bushing if it's coming apart.
In your video you really aren't checking the "sun tube" fit you're checking the fit of the drum on the CS. The drum will rock back and forth like that. Pull the tube out and stick it into the drum and try to turn it back and forth to check the fit. It should be tight. I can't comment on the BTE drum as I've not used one. Looks like a nice piece.
FYI, I see there's scarf cut rings on the CS. Air checking the direct drum can be difficult with those rings. You may have to add some ATF to the lube hole in order to get them to air check.
I'd change the CS bushing if it's coming apart.
In your video you really aren't checking the "sun tube" fit you're checking the fit of the drum on the CS. The drum will rock back and forth like that. Pull the tube out and stick it into the drum and try to turn it back and forth to check the fit. It should be tight. I can't comment on the BTE drum as I've not used one. Looks like a nice piece.
Thread Starter
Joined: Nov 2013
Posts: 6,389
Likes: 558
From: Portlandia
right and without being able to check function or pressures i could only rely on his description "its bound up in 3rd" to hazard a guess.
clutches fine, air tested good with trans goo on the rings
ive never seen a direct drum with that much play in the splines. certainly not in an aftermarket peice...usually they are damn near press fit.
in the video the sun tube is held damn near stationary to the CS axis (obv got a new bushing) and the rock you see is all in the splines
clutches fine, air tested good with trans goo on the rings
ive never seen a direct drum with that much play in the splines. certainly not in an aftermarket peice...usually they are damn near press fit.
in the video the sun tube is held damn near stationary to the CS axis (obv got a new bushing) and the rock you see is all in the splines
Teching In
Joined: Aug 2021
Posts: 29
Likes: 7
I'm actually working on a 400. Done quite a few lately. They come in waves they say.
If I take the drum and turn it upside down and stick the tube in and pull it one way and push it the other. I'd say it's rocking about 3/16". With the gear train assembled and the drum on the CS I'd say the drum is moving pretty close to the same as yours.
He may want to double check how his linkage and shifter are adjusted. I've had guys have shifting problems and one or the other had been a problem. You might not be able to duplicate the problem unless the car is under a load.
If I take the drum and turn it upside down and stick the tube in and pull it one way and push it the other. I'd say it's rocking about 3/16". With the gear train assembled and the drum on the CS I'd say the drum is moving pretty close to the same as yours.
He may want to double check how his linkage and shifter are adjusted. I've had guys have shifting problems and one or the other had been a problem. You might not be able to duplicate the problem unless the car is under a load.
TECH Junkie
Joined: Jun 2008
Posts: 3,203
Likes: 1,391
From: Nitro Alley
The intermediate sprag comes on in second gear, not third. The direct clutch comes on in third. How did the clutches look? How did the direct drum air check?
FYI, I see there's scarf cut rings on the CS. Air checking the direct drum can be difficult with those rings. You may have to add some ATF to the lube hole in order to get them to air check.
I'd change the CS bushing if it's coming apart.
In your video you really aren't checking the "sun tube" fit you're checking the fit of the drum on the CS. The drum will rock back and forth like that. Pull the tube out and stick it into the drum and try to turn it back and forth to check the fit. It should be tight. I can't comment on the BTE drum as I've not used one. Looks like a nice piece.
FYI, I see there's scarf cut rings on the CS. Air checking the direct drum can be difficult with those rings. You may have to add some ATF to the lube hole in order to get them to air check.
I'd change the CS bushing if it's coming apart.
In your video you really aren't checking the "sun tube" fit you're checking the fit of the drum on the CS. The drum will rock back and forth like that. Pull the tube out and stick it into the drum and try to turn it back and forth to check the fit. It should be tight. I can't comment on the BTE drum as I've not used one. Looks like a nice piece.
TruckDoug mentioned a Burn-Out Shifting 1st to 2nd Gear, because doing so will commonly hurt the Intermediate-Sprag.
It is generally recommended to start the Burn-Out in 2nd, and Shift to 3rd in order to save the Intermediate-Sprag.
So yes, the Direct-Drum is being fit to the Center-Support, but it is also being fit to the SunGear-Shaft.
I personally have been only using Press-Fit (slightly shorter) SunGear-Shafts on these builds.
TECH Junkie
Joined: Jun 2008
Posts: 3,203
Likes: 1,391
From: Nitro Alley
right and without being able to check function or pressures i could only rely on his description "its bound up in 3rd" to hazard a guess.
clutches fine, air tested good with trans goo on the rings
ive never seen a direct drum with that much play in the splines. certainly not in an aftermarket peice...usually they are damn near press fit.
in the video the sun tube is held damn near stationary to the CS axis (obv got a new bushing) and the rock you see is all in the splines
clutches fine, air tested good with trans goo on the rings
ive never seen a direct drum with that much play in the splines. certainly not in an aftermarket peice...usually they are damn near press fit.
in the video the sun tube is held damn near stationary to the CS axis (obv got a new bushing) and the rock you see is all in the splines
I do like that the center is Steel (for the Sealing-Rings).
Have you experimented with any Press-Fit SunGear-Shafts?
It aids in reducing the Direct-Drum wobble, and helps the Intermediate-Sprag life.
Teching In
Joined: Aug 2021
Posts: 29
Likes: 7
Trust me, TruckDoug knows his THM400s.
TruckDoug mentioned a Burn-Out Shifting 1st to 2nd Gear, because doing so will commonly hurt the Intermediate-Sprag.
It is generally recommended to start the Burn-Out in 2nd, and Shift to 3rd in order to save the Intermediate-Sprag.
So yes, the Direct-Drum is being fit to the Center-Support, but it is also being fit to the SunGear-Shaft.
I personally have been only using Press-Fit (slightly shorter) SunGear-Shafts on these builds.
TruckDoug mentioned a Burn-Out Shifting 1st to 2nd Gear, because doing so will commonly hurt the Intermediate-Sprag.
It is generally recommended to start the Burn-Out in 2nd, and Shift to 3rd in order to save the Intermediate-Sprag.
So yes, the Direct-Drum is being fit to the Center-Support, but it is also being fit to the SunGear-Shaft.
I personally have been only using Press-Fit (slightly shorter) SunGear-Shafts on these builds.
I am aware on burn out box recommendations for the 400.
Where are you getting press fit shafts? I learned a trick with loctite years ago on this. I had my doubts. But on the first job I tried it on I've had that unit back apart 3-4 times since for refreshes and the shaft is still tight like it's pressed into the drum.
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Thread Starter
Joined: Nov 2013
Posts: 6,389
Likes: 558
From: Portlandia
i'm a big fan of green locktite myself, am just unsure how it would have worked here...it was incredibly loose.
chello, yes I have seen the press fit sun tube just recently in a reid case 80e from jakes i was fixing on. very cool piece.
I am unsure who stocks them. Next time i have my unit apart i'll add one. Right now it's got your CS to direct roller modification and has been fantastic.
did a fluid and filter change and zero metal in the oil..which is a first for me and transbraked 80e's haha
chello, yes I have seen the press fit sun tube just recently in a reid case 80e from jakes i was fixing on. very cool piece.
I am unsure who stocks them. Next time i have my unit apart i'll add one. Right now it's got your CS to direct roller modification and has been fantastic.
did a fluid and filter change and zero metal in the oil..which is a first for me and transbraked 80e's haha
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Thread Starter
Joined: Nov 2013
Posts: 6,389
Likes: 558
From: Portlandia
well the fella took the trans home, reinstalled and still no third gear. he's working on getting a gauge on line pressure and some numbers to me.
I reckon it's something in the VB itself. I have zero experience with the converted iron valvebody type brakes. This is is from TCI (yuck)
anyone with knowledge on these, please let me know what you think
I reckon it's something in the VB itself. I have zero experience with the converted iron valvebody type brakes. This is is from TCI (yuck)
anyone with knowledge on these, please let me know what you think
Thread Starter
Joined: Nov 2013
Posts: 6,389
Likes: 558
From: Portlandia
ok got more clarification. its not actually a loss of third, but rather when shifted to third its put into a bind.
to me it sound like the reverse band is applying. i'm not sure where to look for cross leaks that could cause this.
the original builder lapped the case flat around the CS bolt. I could not put a .001 feeler under a 1-2-3 block layed across that area.
to me it sound like the reverse band is applying. i'm not sure where to look for cross leaks that could cause this.
the original builder lapped the case flat around the CS bolt. I could not put a .001 feeler under a 1-2-3 block layed across that area.
TECH Junkie
Joined: Dec 2012
Posts: 3,618
Likes: 1,328
From: Iowa
Need to know which VB was used.
If it is a Valve body that puts intermediate oil behind the servo to keep the band from applying in 3rd, then you need to find the source of the issue in the intermediate circuit that isn't keeping the band off
as for the spline fit...check a stock drum...they will have rock.
The drum rests on the shoulder of the sun gear tube.
This rock is part of why I cut a bearing into the center support and use that as a means to assist in squaring up the geartrain.
If it is a Valve body that puts intermediate oil behind the servo to keep the band from applying in 3rd, then you need to find the source of the issue in the intermediate circuit that isn't keeping the band off
as for the spline fit...check a stock drum...they will have rock.
The drum rests on the shoulder of the sun gear tube.
This rock is part of why I cut a bearing into the center support and use that as a means to assist in squaring up the geartrain.
Thread Starter
Joined: Nov 2013
Posts: 6,389
Likes: 558
From: Portlandia
to my best knowledge its TCI #221500. the orifice in the bottom of the accumulator bore is plugged with a 1/4 checkball and air tests good.
I called BTE and they say that direct to sun fit is within spec. I check every stock drum to sun and i've never seen one that loose. Just caught me off guard. I'm not sure which direction to go. I feel like it's so sloppy radially that rollerizing the CS wont help much. I may try one of CK's press fit sun tubes.
The customer would like to simply have me replace the VB with a known quantity like a Jakes or Lonnies, but I'm unsure if those can be used as this case is modified at the area where the Vacuum modulator valve was.
Customer is in a pickle, original builder is incommunicado
I called BTE and they say that direct to sun fit is within spec. I check every stock drum to sun and i've never seen one that loose. Just caught me off guard. I'm not sure which direction to go. I feel like it's so sloppy radially that rollerizing the CS wont help much. I may try one of CK's press fit sun tubes.
The customer would like to simply have me replace the VB with a known quantity like a Jakes or Lonnies, but I'm unsure if those can be used as this case is modified at the area where the Vacuum modulator valve was.
Customer is in a pickle, original builder is incommunicado
Thread Starter
Joined: Nov 2013
Posts: 6,389
Likes: 558
From: Portlandia