automatic transmission questions

[jimk]

Not being a huge fan of automatic transmissions I do believe that Maby a automatic might be good for me IF I could use it to pull my trailer.

I don't drive like I stole it or am I going to. I need second gear lockup, maby even first, as I was told that it is possible.

When I drive the truck I have to feather the throttle to give me rpm ( for oil pressure to make the clutches hold) more than 1800. I have a stock transmission and a loose fluid coupling. If the convertor was good in fluid coupling it would drop and so would the RPM. IF I have a heavy load on my trailer and only have 1200 or 1300 RPM the volume in the frount pump does not give the needed pressure to make the clutches hold with a lot of load. The reason to reduce all leakage for sure. I have to go to 2500 or so to make sure I don't drop the RPM to much when I change gears. I would like to know how much torque each clutch pact will hold with a given psi. I could do the math but I am sure that knowledge is all ready out there. Example forward clutches at 65 psi, at 75, 85 etc lock up in the converter at 120, 150, 175, There must be a general rule for how much psi for a given torque for each clutch pack. The torque being limited to the weakest clutch pack.

I would like to go to lock up at 1500 if it were possible. In my opinion the transmission needs more oil pump volume to do what I wont. It might seem like a lot of bs but even a engine mounted oil pump to charge the transmission with enough volume to provide good lubricating and oil pressure at lower RPM than 1800 in overdrive and lockup when towing.

It will probably never happen or cost 6k dollars and I will be rid of the automatic for good. It would be good to have a transmission that would keep the turbo spooled up, as that is the only reason to own a auto for me. jimk

 

[Reb.B]

sometimes its hard to have the best of both worlds. Let me throw out a couple of numbers and advise, and u can take it for whats its worth. Stock VB in a stock transmission is 60-65 psi at idle and 90-95 psi at WOT. Trans go VB kit is 90 psi at idle and 120 WOT, Dunright kit and some others 75-90 psi at idle and 140-165 at WOT. Also the kit provides converter fill up in park and lets u lock up in any gear position.

As far as coverters go, the stock one will work when u apply enough lock up pressure to it, but when pulling loads not locked up the transmission temps get up there quick. I like to have a stockish stall to get the rpm up and the turbo spooled up and then lock it up. Some converters won't let u do this. pulling a load at 1500 locked up might not work. 2000 rpm is a lot better rpm to run your motor at. When doing a transmission rebuild keep these things in mind, make sure u have a 5 pinion, 15 degree rear planet, always change the sun gear, . . all of this is in the OD, and yes u use the OD section in all forwards gears. There is OD and OD direct. OD direct is all forward gears. Ten clutches would be nice in the OD direct. If u have a 94-95, need to go the the late model 15 degree rear planet. Hopes this helps a little

 

[98rammer]

Originally posted by Reb. B

Stock VB in a stock transmission is 60-65 psi at idle and 90-95 psi at WOT. Trans go VB kit is 90 psi at idle and 120 WOT, Dunright kit and some others 75-90 psi at idle and 140-165 at WOT.

on a stock auto with the transgo, 90 psi is a lot. doesn't that leak by the front seal or whichever ones will blow out (like i'm not suppose to go more that 3 1/2 turns on the line pressure to be safe)?



Tom

 

[Snow man]

The last trans go kit I installed came with the 3rd gear seals,and said transmossion removal was necessary to install the seals.

 

[98rammer]

Originally posted by Snow man

The last trans go kit I installed came with the 3rd gear seals,and said transmossion removal was necessary to install the seals.

if you're going to disassemble the transmission for the kit anyways, then why not do all the updates, right?

 

[Jim Fulmer]

98rammer



Your right, you have to pull it apart to do the seal upgrade so when your there why not do the front half update, then you will ask why not just do the O/D section also. Some folks just get the updated front half because of money or there transmission only has a few miles on it and there just looking for something better and there power is not real high, depends on the transmission and how it's been driven. I've said on here before that a wanted James N. to go through my whole transmission when he did the rebuild (Feb 02') and it's a good thing as the direct clutches were slipping and the O/D clutches were Blue, I thought it was the converter slipping but... . nope!



Jim

 

[jimk]

throttle angle

Another problem to overcome for me would power increases, like bigger injectors use less throttle angle. Less line pressure. I don't intend on pulling the hitch of off my trailer to get it up to speed.

How do you change the the ratio of pressure to throttle angle. I have thought that the AFC housing might play a part in helping control the low pressure problems. I cheated a little and made a bracket to hold up the throttle lever so it wont go to the original position when released. I don't have any more wide open throttle pressure, but I have extended shifts and more pressure at low throttle angles. It is just a get by thing any way. So far with 92k miles it is working good.

I have ridden in some trucks that have good shifting transmissions, but never ones that have a 15 to 20 k load in tow. When towing with lighter loads with 3. 54 gears third gear lockup if a little to slow but when I shift the rpms are to slow for 1750 or 1800 ( required pump speed to have good pressure) to go forth gear lock up? thanks for any insight jim

 

[98rammer]

Originally posted by Jim Fulmer



Your right, you have to pull it apart to do the seal upgrade so when your there why not do the front half update, then you will ask why not just do the O/D section also. Some folks just get the updated front half because of money or there transmission only has a few miles on it and there just looking for something better and there power is not real high, depends on the transmission and how it's been driven. I've said on here before that a wanted James N. to go through my whole transmission when he did the rebuild (Feb 02') and it's a good thing as the direct clutches were slipping and the O/D clutches were Blue, I thought it was the converter slipping but... . nope!



Jim [/B]

jim, good points



if i remember right, bill k says that the converter clutch is 40% stronger than any other clutch inside the transmission, however, it gets a bad rep due to internal leaks being present. i can slip the converter clutch and/or bands when in lock up (hence i have the switch and will not use lock up on hard acceleration, too low of rpms, well... basically at the wrong time). i still have the stock converter, but the transmission doesn't slip with my power in fluid coupling (or if the internal clutches are "slipping", it's certainly so little that i don't feel it). maybe it's because of the stall speed not transferring much torque in the lower rpm range that the internals aren't slipping in a major sense.



btw jim, did your transmission slip only in lock up like mine, or did it do it in fluid coupling too?



DTT in the future! constantly learning about what i can get away with now



Tom Pulyak

 

[Jim Fulmer]

Tom, here is something to chew on! James built my transmission for the HP that I was at and to date I have only changed the base pressure and the TV spring for higher shift points. I pulled the pan today to change the TV spring and the was clean! I'm at about 650 HP as a guess on the same transmission and converter and yes I lock it up at 65-70 lbs of boost after the 3-4 shift with no problems.

 

[GLASMITHS]

jimk

If you are just looking for higher line pressures during light throttle why not look at BD's pressure-lock. That is it's purpose, and ofcourse it's intended use is to increase line pressure during e-brake operation. Or maybe just put an old choke cable on it.

 

[jimk]

Originally posted by 98rammer

jim, good points



if i remember right, bill k says that the converter clutch is 40% stronger than any other clutch inside the transmission, however, it gets a bad rep due to internal leaks being present. i can slip the converter clutch and/or bands when in lock up (hence i have the switch and will not use lock up on hard acceleration, too low of rpms, well... basically at the wrong time). i still have the stock converter, but the transmission doesn't slip with my power in fluid coupling (or if the internal clutches are "slipping", it's certainly so little that i don't feel it). maybe it's because of the stall speed not transferring much torque in the lower rpm range that the internals aren't slipping in a major sense.



btw jim, did your transmission slip only in lock up like mine, or did it do it in fluid coupling too?



DTT in the future! constantly learning about what i can get away with now



Tom Pulyak

I have no problems slipping the converter or clutches, But I am very care full. I manual shift when I tow and raise the rpms to 2500 an ease off the throttle and shift to the next gear. I use the lock out button also. The whole thing is just a get by thing. I can make 30 lb boost but I sure don't use it when towing.

I am willing to listen to reason if you have a better way as long as it does not cost 4k . Not for 4 gears any way. jim