Rebuilt transmission issues (reverse)

[dgoodhue]

My 700r4trans was rebuilt by me with a Typhoon Core. I have only put about a one mile of driving the truck on the street plus may may 2 dozen back & forth in/out of the garage. It also has about 6-7 miles on jackstands. It has good pressure in idle (150 psi, 250 psi 1st/2nd) and full TV (300 psi) I tried swap VB with a known good one. I am using Synthetic Type F trans fluid and one bottle of lube guard.

My truck doesn't move very well in reverse. I have to give it gas to move in reverse and the tires turn only couple mph on jackstands (ever other position is about about 10mph idling). On the ground, it will not move in reverse if I give it gas. It will also drive froward neutral (yes the trans cable is setup properly). It kind of feels like reverse is fight with the foward gear.

I pulled the Servo and verified its moving freely and seemingly work properly (thinking its engaging the 2-4 Band), the servo cover seems to push in a similiar amount to my working stock Sy Transmission (maybe slightly tighter)

I was told that maybe the tight forward clutches clearances, maybe causing this problem. Do I drive it some amont of miles and see if I still have these issues? I am just worried something might be wrong and don't want to ruin the trans. I don't feeling like R&R the trans a bunch of times, but I don't really know where to look next either.

 

[jwaller]

Re: Rebuilt transmission issues (reverse)

sounds to me like you cut a lip seal on the piston in the Rev input drum. whats your line pressure in Rev? that will tell you a lot.

if you also had issues with 1st I'd say you might have issues with your low/rev clutches but you don't so I bet your problem is in the rev input drum.

did you install a reduction plug in the rev input drum piston?

you can almost always bet a 700 will move in 1st and rev even with major internal damage. for rev or 1st to not work something is wrong inside.

to fix it your going to have to R&R again and see whats going on inside.

 

[dgoodhue]

Re: Rebuilt transmission issues (reverse)

sounds to me like you cut a lip seal on the piston in the Rev input drum. whats your line pressure in Rev? that will tell you a lot.

did you install a reduction plug in the rev input drum piston?

My pressure in Reverse is 160psi (at idle). Yes, I am pretty sure I did.

 

[dgoodhue]

Re: Rebuilt transmission issues (reverse)

Your pressures seem high. Idle should be 50-65. Full TV in Neutral, 150-ish. Full TV in Reverse 275-325+. Your idle line press seems high.

My pressures are higher because I have .525 TV Valve and stiffer spring in the pump. This wasn't a stock rebuild.

You say it moves forward in neutral. Only thing that can do this is Fwd clutch too tight, or being applied, or O-Run clutch too tight, or being applied. You indicate you know it's tight. This could be the whole problem. If you let it idle in Neutral, with the wheels blocked, the Fwd clutch should loosen up fairly quickly, if it is going to. This will build a lot of heat quickly, if it is tight but slipping. Don't over-do it.

Good idea. Brian Hartman recommended that I drive it for couple miles, then check the fluid smell/color for burning, check it again at 10 miles and 50 miles and put it back on jackstands. My input drum clutches were set approx to .015 and the OD Clutches 0.010 which Hartman recommended.

I have to get some gas anyways, it's really and it's been a long time since I have filled her up at the gas station. (4 years, yikes)

Low/reverse clutch has two pistons. Both are applied in reverse, but only one is applied in Manual Lo. (This clutch is NOT used for 1st gear, so the fact that it moves forward in 1st is not an indication that this clutch is OK. It is used for braking in L1 only. The lo-roller clutch is used for acceleration in first gear). If you have engine-braking in L1, 1st gear, the lo-rev clutch is probably OK. The best way to ascertain lo-rev clutch health with the trans installed is to air-check it with the valve body removed.

As I mentioned, I have only drove it about 1 miles on the road. (two 1/2 mile drives around the block) I have not really figured out if I have engine braking in 1st Gear. At the time I drove it was stalling at low RPM intermittently and I had a bad battery, so I didn't spend much time at those speeds. The first time I probably didn't even have a license plate. In addition to rebuilding the trans, I swapped motors and started running code $59.

 

[dgoodhue]

Re: Rebuilt transmission issues (reverse)

I'm not being critical here, just inquisitive: Why the so-tight tolerance on the Fwd Clutch?

It's applied in all forward gears, so it's not critical, or even pertinent as to how long it takes to engage. But if it drags, it affects Neutral and Reverse. Dragging (too little clearance) is much worse than slow-engagement (higher clearance).

His reasoning is that it will wear through out the whole clutch life. If it's too loose it will slip at the end of the clutch life. I am just going off a recommendation.

 

[rockclone]

Re: Rebuilt transmission issues (reverse)

That is a valve body problem trannys is what i do for work.

 

[dgoodhue]

Re: Rebuilt transmission issues (reverse)

That is a valve body problem trannys is what i do for work.

I doubt it. I tried using a known good valve body out a perfectly function Syclone transmission and it acted the same.

I drove my truck for a few miles today and it no longer drives in N and Reverse is working much better,

 

[cloneman315]

Re: Rebuilt transmission issues (reverse)

put it in a box and ship it to john.

 

[turbodig]

Re: Rebuilt transmission issues (reverse)

I doubt it. I tried using a known good valve body out a perfectly function Syclone transmission and it acted the same.

I drove my truck for a few miles today and it no longer drives in N and Reverse is working much better,

I suspect the uber-tight clearance was a large share of the problem... keep driving it, and an eye on temps.

I have similar not-quite-right after rebuild issues with my trans as well. About the same amount of downtime, too.

 

[dgoodhue]

Re: Rebuilt transmission issues (reverse)

My TCC lock up isn't working and I can keep the trans in 1st gear or get 1st gear braking. (I have second gear/braking) I think the linkage is slightly off. It doesn't quite seem to fully engage 1st.

I am going to have to drop the pan to check the wiring an/or TCC solenoid.