Hey guys,

I'm trying to come up with a plan of attack for my C6 transmission. It's never been overhauled or gone through since I've owned the truck. It's always seemed to hold up with no major issues and there were far more pressing things that needed attention.

I have a 460 that runs really strong. RV cam, edlebrock performer intake, holly 750 carb. The transmission is from a 75' truck I believe, I remember looking up the numbers from the tag that's on it.

I let the truck warm up a bit before I drive it and until it gets warmer it seems like the gears have a hard time shifting, especially from 2nd-3rd. This has kind of been the case since I bought the truck but lately it's been annoying me since I've made this my daily ride. I'm not sure if the gearing is wrong for the motor, maybe I need a shift kit, tranny rebuilt etc. I'm not looking for an exact answer to the problem but maybe a direction to go in. I recently booked a job (I'm a freelance web guy) and have a few extra bucks to spend on trying to fix this. Between 1st to 2nd, and 2nd to 3rd it just seems like it revs to high before it shifts into that gear. 3rd to 4th has no issues and it cruises on the freeway like a dream. It's just the city traffic that is an issue and forget flooring it and trying to peel some tires. It revs high then dumps into the next gear and takes a bit for it to get it's pickup again....

 

It might be time to have it serviced and cleaned. Also - stupid question - have you checked the fluid level - warmed up (like driven for 10 miles), run through each gear then placed in park, engine running at idle?

There's no forward 4th gear on a C6 btw, are you sure that's what it is?

 

It almost sounds like it might be slipping, but that particular sensation is a bit difficult to describe. I think that the first thing I'd do is drain the transmission and converter, replace the filter and modulator, and fill the whole thing with fresh fluid and see what you get. That's the easy stuff and what you should rule out first. If it still doesn't seem right, then you can move forward from there.

 

It does feel like it's slipping and yes it is hard to explain because I haven't experienced that in an automatic before. On imports I've had that were 5speed you can easily tell when the gears are slipping.

Yes, it had fluid and I've checked it after warming it up, driving it etc. I was going to drain the fluid and all that but have been ultra strapped for time lately with all this work coming in. I bought a rebuild kit for my carb a week ago and it's still sitting there in the box. I'm a little leery of taking it to a shop since everything else I did myself but didn't want to let it go to much longer. I know these are pretty bulletproof but the slipping or just how it's shifting into gear was a concern.

On a good note... a client of mine who has wired a lot of old cars is going to help me with my truck. So all new wiring in another few weeks. I just gave him a discount on a website I am building for him. So I get paid for the site, and get to learn how to wire up my truck .=)

 

So I finally got around to checking out the transmission pan and all. I was planning my attack and just checking things out. There is no drain plug so I'm assuming this is going to be a very messy job.

How do you drain the converter? I've been trying to find stuff online with no luck yet. Just very general information. I have the gasket, and filter but what is the modulater?

 

most convertors but not all have a drain plug on the front of them. you have to remove the front inspection plate and then rotate the engine until the drain plug is at the bottom.

a lot of the transmission pans have a rubber plug on them that you can remove to drain the fluid without having to drop the pan. if you don't damage it too much you can re-use it or buy another one if damaged.

rgds
Mike

 

Look on the bottom of the front side of the transmission bellhousing right behind the engine oil pan. There should be two bolts holding on an access cover. Remove that cover to expose the flexplate. Use a screwdriver on the ring gear teeth to rotate the engine. At some point, you will see the torque converter drain plug. It actually sticks through the flexplate. Turn the engine until the plug is at the bottom and pull it out to drain the converter.

The modulator is a small canister mounted at the passenger's side rear of the transmission case. There will be a vacuum line going into it. Try replacing this only if the fluid and filter change doesn't help.

 

Do not be surprised if there is no drain plug in either the trans pan or the converter.

 

Yeah ,I didn't see any sort of drain plug on the pan and I'm hoping there is something to drain the converter like someone else here mentioned. I've never really touched much on this type of transmission but I'm ready to see whats up under there.

I was going to just drive my truck up on the ramps I have so I can get under there and take off the pan and go from there. I have 4 quarts of Type F but am assuming I'll need more if I drain the converter too. I'm assuming this is pretty much like changing my oil with the exception of putting on a new gasket. Drain it, new gasket, new filter, fill it up and turn on the truck to let it cycle a bit.

I'm really hoping the helps out a decent amount. I'm still saving to get an IFS set up.

 

Have a BIG bucket ready when you drain that. There's 24 pints of fluid in the beast (at least there should be). That's 3 gallons!

 

Gulp...

Well I have a ton of shop rags handy and two pans to catch fluid.

 

Soooooooo, I broke down and took the truck into a transmission shop.

I was getting ready to start working on it and was grabbing my tools and just didn't get the good feeling I usually get when I start on something. So I did some research on Yelp.com and found a shop nearby where the guy was awesome. He let me hang around the shop and showed me the in's and out's of what they were doing. Took me on the test drives, and had me stand underneath the truck to point out what was being replaced and what was what. I asked to hang around so I could learn some things. I have ramps for the truck but it seemed like a better idea to take it to a place that specializes in that as opposed to me testing it out.

Drained the converter and pan and I saw a handful of metal shavings in the pan. He said it was probably due for a rebuild and gave me an awesome rate. Although he said "Lets do this and see how much life and performance we can get out of it". He actually filled it up and drained it twice to help wash out any contaminants that might have been stuck. Replaced the filter and gaskets and he ordered a new modulator but before putting it on said "This other one doesn't look bad, let's see if we can't adjust it to save some money". I didn't know the bands? inside them were adjustable with a screw like on the power steering box or carb. So he tweaked it a few times, tested it, then adjusted again. It runs awesome now. I feel like it's a lot faster and more powerful but this is probably because it wasn't shifting like it should have and I was loosing a lot of power. Now it's really strong through the gears and sounds and feels great. At the end he said to me "Does $100 seem fair to you? we got it running well, you learned a bit and if you bring it back we'll just take 100 off the build." Even better...I called him at 8am brought it in at 10am and had it ready to go by 3pm.

Great experience and I'm glad I listened to my gut and took it in. Just one of those "feelings"

 

It's always nice to deal with folks who that auto repair is an environment where folks need to be treated with respect. This sounds like a great find.

I had to cringe when I heard the part about the metal chips. But maybe he got you a few extra miles before the rebuild.

I'm not sure how much your quote was but I had my C6 rebuilt about 3 years ago an it needed everything - was all burned up. I had it completely rebuilt and new torque converter for $1100. I had it out of the truck already and reinstalled it after my engine rebuild! I thought that might be a little high but I guess it depends on who does it. Apparently that's about average for SoCal.

 

Hey there,

Yeah it was a good find indeed. I drove her around town today to run some errands, hit the gym, go get lunch and I was still surprised how much more efficient she runs. It's just nice to have something working as it should again.

He quoted me $1000 to rebuilt the entire transmission "a level above stock" meaning he would beef it up a bit for my truck. He said it would take two days and minus $100 that I paid for the service. So $900 to have it rebuilt, them take it out and reinstall, and in less that 1/2 of a week is a pretty phenomenal deal. I'm hoping some clients pay me sooner then later so I can just do it and move onto the next thing...wiring.

 

Hang on to that guy! That's a great price on the rebuild.