ok, I hope the experts chime in..

i rebuilt my 4r100 myself. 1st time i re-installed it, I had no 2nd gear.. All other gears worked fine.

drove it less than 2 miles.. slowly..

Took it back out, found i built the Intermediate Clutch wrong. Fixed. At the same time, found a stuck valve in the accumulator VB, Fixed that, at least i think I did. all the valves snapped back under spring pressure.

Put the trans back in, Drove forward, all forward gears work.

Drove 10 miles normally, w/ some time spent in all speed ranges. Temps good, outside temp was 73F



M1 = i get good engagement and engine braking

M2 = I get 1st and 2nd, seems normal

OD = Normal shifts, 4th is a little soft, but always was.. TCC lockup good

OD (Cancelled) = Normal 1-2-3, with lockup in 3rd Worked the button multiple times, shifts down, and back up normally.

N = No movement, no creeping.. Normal.. as far as I can tell.

R = No reverse, or is binding in reverse, not sure. worse when up to temp.

P = Normal, no learching or creeping.. No stalling.

the OD light never blinked, so I don't think it is electronic..

So, this is where I need some experts..



Obeservations and research done..

Since M1 works and holds with engine braking. L/R clutch and seals are ok.

Forward clutch is ok since i have ALL forward gears, No slipping that I can tell. no creeping in Neutral, so the clutches are not fried.. New fluid is still perfect. I'll have to re-pull the pan to see if there is anything on the magnet.

I think it could be some stuck valves in the VB also.


Any other suggestions I can look at without pulling the trans agian?

thanks in advance.....

 

Did you get the small metal plate with the three 8mm bolts at the bottom side of the valve body tight?

It seals the low/reverse circuit, its a common no or slipping reverse after repair issue.

 

Funny you should mention that.. My son helped me put it back together after i fixed the intermediate clutch. I supervised, and helped with torquing the VB's down. We left those three bolts a bit loose while installing the VB's. When we got the pan on, I asked him directly, 'did we torque those three little bolts on the retainer plate?" He said "yes" with a confident tone, but you would have to know my son. He is 16..

I will pull the pan tonight, and i bet that those are loose.. That would be a GREAT thing.

Thanks. I needed a break.. I hope thats it..

Edit for another symtom related to these : Say these bolts were left VERY loose would it cause a rattle, especailly at idle, in park?

 

Ok, so that is one thing.. they were only finger tight. torqued to spec.


But, once warmed up, reverse shudders and will not roll by itself in gear. It will move, but have to give it a bit of pedal, really just a bit, not floor it.


Tightening the plate made all forward gears better, shifts are firm, not hard, no banging. i liked how it shifts in the forward gears.


The only thing i got left is the O.D. roller clutch, which is in hold in reverse and manual 1. when i was building it, i tested by hand each roller clutch and sprag. all worked fine as far as i could tell.


Reverse is good when the trans is ambient temp, even as low as 120° i can't reverse normally.


So, any more things to check before i pull it for the third time?

 

So i went for another test drive. cold, reverse is good.


Drove for 15 minutes, got it warmed up, mind you, ALL forward gears are good, shifts are nice and firm, no banging, on time, TCC applies normally, holds power, downshifts to third normally under heavy throttle, OD cancel works normally, with engine braking when coasting in OD until i hit the brakes, then Coast Clutch un-applies and engine braking stops, like normal. never stalls at stops. Downshifts work just as good as upshifts.




Reverse, after warmed up, engages. You can feel it,but the apply is not as strong as when cold. in reverse with no brakes, the truck will not move by itself. Add Rpms (400-500), and you feel a bump, and immediately starts moving, but does not continue to roll once you start moving. you let off the gas, it quits moving. give it some more gas, you get the bump, and starts moving again. Will not roll in reverse, does roll normally in all forward gears.


Theoretically, if the forward clutch is packed too tight, would it continue to spin in park,reverse and neutral?

 

Ok. Have a new theory.


What if a return spring snap ring popped loose? if one did, it means that after the first apply,it would not fully release. Causing a bind up when i put it in reverse.


To test this theory, here is my test plan.


If you look at the apply chart in the ATSG rebuild manual, the clutches apply in a linear fashion, forward, intermediate,direct, then OD, and coast as needed..


So, this how i'm going to test.


The truck has sat all night, so any residual pressure has subsided, and no clutch has had pressure to apply. (this goes with my experience that i will have normal reverse, with what i thought was a cool/warm issue).


To start the test, i will shift to reverse to verify normal operation.


Then i will shift to drive, not moving the truck, with the brakes on, then shift back to reverse. if reverse still works normally, its not the forward clutch, as it is the only clutch applied for Drive -1st gear.


Pass that test, and i will drive the truck in drive until it shifts to second, and immediately stop, and go to reverse, pass that test, and it's not the intermediate clutch.


Then i will drive the truck again, until i reach 4th gear.Stop immediately,and test reverse again. Pass that test, and it's not the OD clutch.


Next, drive truck with TCS button on. (OD off), drive until i hit third, and fast enough that when i let off the gas i feel engine braking. This means the coast clutch applied. Again, stop immediately and test reverse.


What about third? (your thinking).


Reverse and third share Direct, so if reverse works, and Third works, direct is ok.


So, if my theory is correct, i should fail one of these tests. my money is on Intemediate clutch return spring being broken, or the snap ring came off.


Whats your opinion?

 

If it works normally when cold but starts to fail as the fluid warms, it's probably a leak. The fluid thins as it heats up making the effect of any leak more pronounced as the apply pressure for the affected clutch bleeds down and allows the clutch to slip.

 

I dont think it is slipping, i think i have a bind in reverse, third works great, reverse uses the same clutch.

 

I dont think its the intermediate return spring or snap ring.

It sounds like you may be dealing with a cross leak, meaning that oil pressure is leaking from one circuit to another. The most common spot on these is the center support area, the center support on these feed the forward and direct drum. How tight are the center support bolts that go through the case? These bolts can warp the case under the valve body if they are too tight, they should be torqued to 72 inch pounds and the case should be checked with a straight edge after the bolts are installed.

Other area that can cause reverse problems is the valve body, check the valves in the accumulator section of the valve body, especially the small valves and springs that are deep in the bores. Also there is a low/reverse modulator valve in the main section of the valve body, make sure its ok and check the small valve in the aluminum sleeve when you pull the valve train out.

 

Well, My theory was not correct.. I got inconclusive results from my experimental test.

I pulled the Trans, again..... Disassembled all the way. (left all the clutch packs and seals assembled that i did not have problems with).

Found my problem, inner seal on the reverse piston was installed upside down. the lip was facing the wrong way.. so when pressure was applied, the seal would collapse inward, creating the leak.

Reversed the lip seal, re-assembled all of it, got it back in the truck, but it got too late and dark to fill will fluid and test, so will do that tonight.

I'm getting better at this, as it only took me 18 hours to pull it, tear it down, put it back together, and re-install. (no lift, in my driveway, on jackstands.)