tranny question

M

Matthew Little

New member
My tranny does not engine break. When you shift my truck down it free spins and does not slow the truck down. You can give it gas enough to make it start pulling. Stock tranny,don't know if it has been rebuilt, but shifts very nice and has a kb 3000 stall converter,did the same thing with the stock one. Any guesses?
Thanks, Matthew
 
B

Blake

Guest
Overrun clutches burnt or overrun clutch piston seal damaged.
 
B

Blake

Guest
Won't cause a failure unless you are racing it as driveline integrity is at its best when in D and this is because the overrun clutches would normally be applied.

Overrun clutches burn up for the same reason any other clutch burns up. Fluid gets cooked, viscosity breaks down, clutch hits the steel, burns up.

Later.
 
Tooky

Tooky

Serious about performance
My original tranny has worked flawlessly for 60,000 miles and over 1000 quarter mile passes. However I just lost engine braking a few weeks ago exactly as you described. I have every cooling mod you can do (largest custom B&M cooler you can get, remote filter, frequent fluid & filter changes, Mobil 1 ATF, deep pan). My temps never got over 180 drag racing, and never over 140 cruising. Once I lost engine braking my shifts stopped being as good and my TCC Lock was weaker.

I drained the pan last night and the fluid was totally cherry. I unbolted the pan (what a bitch with the Derale tubes blocking access to the bolts hidden by the rear tranny crossmember) and found lots of metal debris. The magnet was like a porcupine filled with "fool's gold". Whatever controls engine braking evidently shattered.

I cleaned the pan and put new filters (tranny & remote) in and new standard Dexron III (not Mobil1) fluid. Now the tranny shifts better and the TCC lock is much improved. My engine braking is still gone and I expect the tranny to fail within the next month, counting on a rebuild over winter. Since I put the new fluid in last night, I went drag racing tonight and set a new record for fastest Syclone on stock turbo. So it is possible for the tranny to last a while yet.

Hope this helps,
 
S

skata

Donating Member
TookyCat said:
Whatever controls engine braking evidently shattered.
Click to expand...
your over-run clutch hub probably broke. thats the problem with driving in drive, the over-run clutches are applied and that puts pressure on the hub, mainly during shifts. the result is firmer shifts, but that part of the hub is a weak connection. breakage can easily occur if the forward sprag slips at all.
 
M

Matthew Little

New member
tt

tt

Well glad to see I am not the only one, but sorry for your tranny. I am also losing some trans fluid from somewhere too, seems like it's only under heavy load and is from oil pan to rear cross member under xfer case, but tranny and xcase looks dry, stop running at the track because of that, but my intakes are off right now and thinking of putting the l35's on since I am this far in it. I put leak finder from GM in it and it seemed to be everywhere, so wtf?
 
B

Blake

Guest
There's a new design sprag out that takes care of many of the failure issues regarding that problem.
He lost engine breaking though to some extent. I'm leaning toward overrun clutch piston seal. It very well could be a bad sprag component though as much as those fail but those normally result in additional drivability problems as well.
Blake
 
S

skata

Donating Member
hey blake,
when i said his over-run hub broke, i didnt particularly mean the sprag.
there is the main part of the hub(with the sprag inside) and then there is the other piece that indexes with the over-run clutches, that part has teeth on it that match with the main part of the hub and is held on with a c-clip.
if you look at figure 122 in the atsg manual and look at part#639, those teeth on the inside diameter are what probably sheered in tooky's trans. since tooky said he found lots of metal debris when he changed his fluid that would be my guess. that connection there is pretty weak and will easily break if the forward sprag slips for a little. (been there done that)
as far as matthew littles trans, i'd say to change fluid and filter to see if there is any metal debris. if not then its more likely a seal went bad.

HTH
 
B

Blake

Guest
I'm with you brother. When I refer to the sprag, I mean the whole assembly. Inner and outer races, overrun clutch hub, snap ring, element, and front sun gear.
The part you refer to as sprag I just call the element.

A little side note is that you can no longer get just the overrun clutch hub from GM. You must buy the new sprag. GM calls it a Hi-Torque sprag.

The sprag assembly I was talking about is a new unit that GM started making. It was completely made over with tighter tolerances of the overrun clutch hub and inner and outer races so that the element would run perfectly true to the rest of the drive line. They also started press fitting the sun gear into the inner race. I have a complete old style and a new style. When comparing the two there is a LOT of slop in the old style.

Something I do in addition to the new sprag is take the single cage SKF element out and put in the BW dual cage element. The BW held up under the old style very well where as the SKF would fail. So putting in the new style BW in the new sprag increases its safety factor even more. This is due to the dual cage element as well as the squared edged "washers" that the "dogs" of the element ride against. In the SKF, they are rounded.

Skata knows this stuff already, this is just for others reading this conversation that I may have confused. I'll take some pics of a sprag assembly taken apart and show where everything fits and where the problems were as well as compare the two elements, if you guys want to know. I'll also point out where the different clutches ride on the sprag. It's amazing how much the tranny relies on this part. 99% of the rebuilds out there just have the element replaced and not the whole assembly so it may be of interest.

I'll do a little quicktime video(my camera can do 30 sec shots) of proper rotation of the sprag when assembled correctly as well.
George
 
M

Matthew Little

New member
tranny

tranny

So,I changed fliud a few weeks ago and there was some buildup on the pan, I thought it was some clutch mat. Are you guys saying this is a first sign of tranny failure? Got the heads off doing l35's and dp,roller rockers,etc. This is going to suck to get that done and have the teranny go out. Any ideas on my fluid leak? My buddy does his gn tranny and I am thinking of doing mine,if I have to. What do you order tranny parts for a 4l60 or 700r? I have seen guys calling them 700's, but gm calls it a 4l60 non e.
Thanks, Matthew
 
B

Blake

Guest
THM700/700r4/4L60
All the same thing.
4 speed,longitudinal mounting,60 strength rating(ie. 4L80 is one step stronger than the 4L60).
4L65 is slightly stronger than the 4L60.
 
B

Blake

Guest
Not to sound like a dick but do a search.
You will find many entries.
Too many to list here.
 
B

Blake

Guest
Sprag

Sprag

Here's the sprag lineup. This is the same kind of sprag you will find in stock Sy's and Ty's.
aaa.thumb.jpg

Left to right: Overrun clutch hub/Outer race/element/inner race/sun gear
(snap ring not pictured)
Fullsize
http://huryde.station180.com/albums/album09/aaa.sized.jpg

The overrun clutches(2 of them)ride back and forth on the overrun clutch hub.
The forward clutches(5 of them)ride back and forth on the outer race.

Here's the element
aab.thumb.jpg

This is a BW element and notice the little square notches over each "dog" pointed up. This is the correct arrangement for proper function.
Fullsize
http://huryde.station180.com/albums/album09/aab.sized.jpg

Here's a comparison of BW(Left) and SKF(Right)
aac.thumb.jpg

Fullsize
http://huryde.station180.com/albums/album09/aac.sized.jpg

Here's the 2 problem areas in the element itself(washers removed).
#1 Single cage of the SKF doesn't keep each individual element aligned as well as the Dual Caged BorgWarner.
aad.thumb.jpg
aae.thumb.jpg


Fullsize SKF
http://huryde.station180.com/albums/album09/aad.sized.jpg
Fullsize BW
http://huryde.station180.com/albums/album09/aae.sized.jpg

#2 SKF uses washers that are rounded where the BW has squared washers to engage the inner and outer races more securely.
aaf.thumb.jpg

BW with the square edge
Fullsize
http://huryde.station180.com/albums/album09/aaf.sized.jpg

aag.thumb.jpg

This shows the rounded edge of the SKF.
Fullsize
http://huryde.station180.com/albums/album09/aag.sized.jpg

Many failures resulted from putting the new SKF in the old sprag design. Don't do it.

I have a new design sprag coming in Monday and I'll show the areas they improved it.

If you go back to the very first picture of the lineup, you will find the overrun clutch hub on the far left.
Skata was referring to this part.
What can happen is either the little tabs that engage the inner race can break off, the inner teeth of the overrun clutches themselves can shear off, or the overrun clutches' teeth can scrape metal off of the overrun clutch hub's teeth. All of these can result in metal in the pan and a wasted element.

Later
 
M

Matthew Little

New member
tranny

tranny

Yeah I just haven't searched yet, hoping not to have to do the tranny thing,but 90k+ stock tranny, may be coming soon.
Thanks, Matthew
 
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