C4 reverse when cold, no reverse when hot

[biggercb]

I have a recently rebuilt C4 installed. When it is first started up, reverse works well. It's a solid shift, and it has plenty of power. During/after warmup, the shift to reverse gets "muddier" and eventually loses all power in reverse. When you rev the engine, it will have a sort of studder in reverse, but no real power. I have driven around the neighborhood and it does seem to have engine braking when I leave it in first. Manually shifting to second seems to work just fine. It will shift into drive just fine as well...but I haven't had it out on the highway to test and see how well it is shifting between the gears.

Fluid is correct, I am checking when warm, at idle, in park. I added about 10 quarts total between the initial quart or so in the torque converter.

I have been in touch with the guy who rebuilt it, but I have moved a couple hours away since I picked it up. I was hoping to avoid trailering it back up there if there was some knowlege on here I could tap into.

Thanks!

 

[DirtDonk]

I’m glad you detailed the method you use to check the fluid. That was going to be the first thing I suggested because it sounds like it’s low on fluid.
Do you have a mix of parts perhaps? Possibly the wrong dipstick?
That 10 quarts seems about right from my memory. But also may be a bit on the shy side, because my memory of C4’s is not so great.

Maybe one of the C4 gurus will chime in with the exact amount, since I am not near one of the charts at the moment.

What about any modifications, such as a deeper pan for example? And is it a stock original bronco transmission? Or one swapped in from another vehicle?

 

[biggercb]

I’m glad you detailed the method you use to check the fluid. That was going to be the first thing I suggested because it sounds like it’s low on fluid.
Do you have a mix of parts perhaps? Possibly the wrong dipstick?
That 10 quarts seems about right from my memory. But also may be a bit on the shy side, because my memory of C4’s is not so great.

Maybe one of the C4 gurus will chime in with the exact amount, since I am not near one of the charts at the moment.

What about any modifications, such as a deeper pan for example? And is it a stock original bronco transmission? Or one swapped in from another vehicle?

It isn't the original transmission to this Bronco...but it did come from another Early Bronco. THe dipstick was purchased from Tom's Bronco several years ago....same with the flexplate. This bronco came to me with an NV4500 in it. I swapped everything to a C4. It ran fine for around 3000 miles, then I destroyed the front pump climbing the neighbor's retaining wall. Stock pan as well.

 

[Broncobowsher]

How is engine braking in manual 1st gear? Mimic what reverse does?
I would do a band adjustment first. Mainly the low/reverse band. After that things are probably going to get a lot more invasive.

 

[biggercb]

How is engine braking in manual 1st gear? Mimic what reverse does?
I would do a band adjustment first. Mainly the low/reverse band. After that things are probably going to get a lot more invasive.

Engine braking in first is consistent. It seems strong without regard to temperature. It's only the reverse I am having trouble with. I'll likely load it up and trailer it to the original transmission rebuilder. Thanks for the help!

 

[DirtDonk]

Does the dipstick go into the pan, or the case of the transmission? Well, I guess it is probably the pan, since you bought a bronco dip stick and it fit.
Just that some swaps used car transmissions that had the case fill. That should be a completely different dipstick.

I wonder if the type of transmission fluid is enough to cause this kind of a problem as well?
I know they originally used type F, but if the clutches have been replaced with something that prefers Dextron, I wonder if it would act up.

Sounds like an adjustment is your good first step.
Good luck!