My tranny seems to slip into gear on all gear shifts. If I use the tow haul mode it seams fine... The truck does a bunch of towing in the summer and I am woried that I am going to have to rebuild it. It has 70000 miles on it and I just had the transmission filter and fluid changed. Everything looked fine. The slip was there before the change but is now more frequent. Whats the deal!!!! When I bought the truck they said it was the slip yoke because it was some kind of bad metal... Only it keeps getting worse.

 

Elaborate on "slip into gear on all gear shifts" for me.

How much are you towing?

 

I tow about 12 times a year a 26' camper maybe 100 miles round trip each time. The slipping occurs on acceleration or from a rolling take off like turning a corner. It's only a brief slip but the engine revs like its in neutral for just a bit. After I posted the original message I went for a ride. I noticed that it was almost not there when the truck is cold, but showed up more when it warmed up. So far I haven't had any problems towing but the seasons begining for camping and I want to try and fix any problems before hand. Thanks for any help!!

 

Sounds like the clutches are slipping...

 

How heavy is that camper?

Does this slipping occur with or without that load?

I'd have to ride in it to tell you exactly what's up but it sure don't sound like a "Slip Yolk" problem to me at all.

Now you said this problem is gone when you have the "Tow/Haul" mode on correct?

If the problem is corrected with Tow/Haul which boosts line pressure you could have a few things I'd look at...

Put a pressure gauge on it and see what it is. Should be like 55psi low. You could have a bad pump or bad pressure control solenoid.

Test the shift solenoids next

If that checks out, I'd consider tossin' in a TransGo shift kit. Just set it up for the HD/Towing shifts. Use the 'Vette apply servo and the Fairbanks billet OD one. That will increase the fluid flow to the forward clutch, 2-4 band, and the 3-4 pack.

 

Yeah perhaps the 3-4 pack is going also, I highly doubt it's the forward pack as even in HiPo situations those are usually never effected. When you shift from P or R into D or OD the forward pack in engauged...

 

Thanks for the places to go. I'll check it out as best I can before taking it anywhere. I hate going to get something worked on I know nothing about. It seems the people around here that work on transmisions only want to do rebuilds and not fix individual problems.

 

It just seems that you've hurt that tranny and may be able to get it to last to 100K mi, maybe. Test it out and if all is well... I'd try a TransGo...

 

I would bet on the band/drum and the 3/4 clutches.

The band is applied in 2nd and OD. In first, you low gear clutches are applied, when it shifts into 2nd, the low gear clutches are still applied, but the band applies and stoped to drum from tunring. That's where the vette servo comes in to play, applying the band. When it shifts to 3rd, the low gear clutches are released as well as the band, and the 3/4 clutch pack is applied. When it shift to 4th, the band is applied as well as the 3/4 clutches.

Does it slip on the 1-2 shift? 2-3? 3-4? Does it slip in any specific gear without shifting?

If the tow/Haul button does fix it, you might could band aid it for a little while by installing a transgo kit.

 

I could have sworn the Forward pack was always engaged in 1-2-3-OD? My Ford trannies do release the Forward pack once in 3rd but I thought the GM 4L60E always kept engaged?

If you do indeed have to rebuild the 3-4 pack (prolly) I'd go with that Red Eagle 9 pack and run 8 in there to keep the shifts more mild in your tow vehicle. I'd run 9 but that may be a lil harsh for ya. If you tranny guy says the stock pack is enough... do an aboutface and leave there ASAP. The Altos are much better frictions than I thought, once I read into them they are very nice and trick pieces. They are slightly thinner like .063 vs .074 I think but with the addition of the 9th clutch they have more capacity than that Blue Plate Special setup.

8 or 9 is still more than GM has. I can get you the clearances if need be on the 8 and 9 pack...just lemme know...

GM also has a revised 3-4 pack found in the 4L65E AND I think Raybestos now has a 14 clutch pack of single sided frictions called the Z pack I believe. Your choices are more optional now.

You could run a Kevlar band or that Alto Red, either are great choices. Stick with the stock width so you can keep the included drum. Also go ahead and get the input drum renforcement setup and the HD Sun Gear Reaction Shell.

....this is all of course if you have to go through it...