727 upshift mystery

DKindley

DKindley

Member
Hello Gentlemen its been a while since I posted up. You guys were such a big help that my scout has been running great for a while. New issue though I'm hoping someone can help me with. So for a little back story my teenage boys have been taking turns daily driving my 75 SII to school for the last couple years. Suddenly they came home saying the scout is making noises. Long story short, they were doing nuetral drops to spin the tires!! I know right. We tore it apart and the sprag was toast and the cluthes were all shot. We completely rebuilt it with new bolt in sprag, and a shift kit. Put it back together and test drove it.
Problem is now it will stay in 1st gear when the throttle is applied. If i let off the throttle and coast it will shift into 2nd and direct. But once its in 2 and 3 it slips. Any ideas? I'm suspecting the governor circuit, but it does go into 2-3 when coasting?
 
Just for clarification, I've tried the following:

Warmed it up, checked fluid idling in nuetral- at full mark
Adjusted the kickdown linkage- 1/4" gap at idle, 1/16" left on
shaft at WOT per MR. Mayben's previous posts
I used the Munroe book by the letter when I rebuilt it, so I know the bands are correct. Torqued to 72 in lbs, backed off 2 1/4 turns on the kickdown band and 2 turns on the low/reverse band
 
Seems like I’ve stumped everyone? Here’s my plan of attack, let me know if it’s a good one. I’ll hook up a gauge to the governor port and test pressure. If that checks out I’m going to pull the valve body and check all the valves to see if one is sticking. I feel like I just don’t have enough line pressure to lock the clutches in 2 and 3? If anyone has a better suggestion please let me know.
 
Did you bench test with compressed air applied to the assorted ports to make sure servos and clutches were applying/releasing properly?
 
Scoutboy, thanks for replying I thought maybe I scared everyone off. Yes I did air check the clutch packs and I could hear them popping closed. The servo ports moved the servos also. I was re-reading the shift kit instructions and I did fail to replace an oem spring with a kit spring. I seriously doubt that’s the issue though.
 
Not skerrd. Just didn't see this until a little bit ago. I don't think there are that many active members who've had their hands inside a slushbox lurking about here either. Will this trans downshift from direct to 2nd when you goose it at say 40 mph? Does manually bumping the lever up from 1-2-D as you accelerate make any difference?
 
I’m sure your right, I’ve only been into mine out of necessity. Well it won’t upshift at any speed if it’s under throttle. Goofy thing is if I let off the throttle and coast, it will shift into 2 then 3. But if I give it throttle it slips or kicks back down into 1 depending on speed and amount of throttle.
 
I was thinking that at first but I talked myself out of that because it slips once it gets into 2/3. I guess I won’t know until I get a gauge hooked up?
 
Do you think too much line pressure would prevent the clutches from holding? Kind of seems bass akwards to me but I may be over thinking this
 
I wouldn't think so either. You've got some pressure readings to take. Don't just do the governor. Take line pressure as well as front and rear servo readings. Refer to the Munroe book as the procedure is well explained there. My WAG is something went wrong with your VB assembly.
 
Ya it seems most likely that I jacked up the vb somewhere along the way. I had a nightmare last night that the input shaft sealing rings may have broken when I air checked the clutches. I’m thinking that would also cause 1st to slip and I didn’t hear an air leak when I was checking them. Thanks for the input and letting me bounce ideas off ya
 
So I hooked up two gauges tonight. One to line pressure and one to the front servo port. Oh boy, here we go. Line pressure read 90psi at first! Did drop down to a steady 75 but that’s still way over the 54-60 the book shows. Also I didn’t get any pressure from the front servo port? I stopped there for tonight because that’s clearly no bueno. The shift kit might explain the higher pressure but not the front servo not pressurizing. Has anyone seen this situation before after installing a shift kit?
 
That LP reading was at idle right? In what gear selector position? Were you driving or did you have the rear wheels off the ground so you could put the thing in gear for the front servo reading?
 
I had it on jackstands. I disconnected the kick down linkage and shifter linkage. Set rpms to 1000 and put selector in high(3). I got under there and took the readings. I forgot to mention the best part. Moving the throttle pressure valve did nothing to increase pressure.
 
Haha yeah no doubt. I could pretend like I know what I’m looking for but really I’m just gonna start at the beginning of the vb tear down section. Then work step by stinkin step through again. Hopefully something jumps out at me. I really don’t think it’s an internal problem so at least I don’t have to pull the tranny again. I do think I’ll tell the wife (Mrs Hayek too) that I need a new SO 1/4” drive ratchet to do the job right. She loves the Scout too so I should be good! Thanks again Scoutboy
 
Whoa. Well, you're a lucky man in spite of the slush box woes. Any shmootz that wasn't removed from the passages, mismatched springs or check balls in the wrong places. There's a lot that can go wrong inside that damn brain.
 
So I took the vb off and went over it again with a fine tooth comb. I did have the wrong spring from the shift kit on the governor pressure regulator valve so who knows. I air checked the clutch packs again and I’m hearing air from inside? How much of a leak is acceptable?
 
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