type of transmission

[Lt.Del]

I know there was a diagram posted on this site some time back that displays what type of tranny you have depending on the pan shape. However, I need to know what type of tranny Ihave in my 91 GMC 4x4 5.7 suburban.

I beleive it may be a 4l60e or a 4l80e.....I don't know the difference.

I have quite a pan leak and need a new gasket.













Any help would be very much appreciated before I go to the autoparts store and get the wrong gasket/filter.


Also, can anyone tell me from the RPO codes whether I have an R2500, or V2500?



Mason Nation
 

[Blazin]

The 4L60E and 4L80E have a a good size wire harness on the drivers side, its what is called a pass through connector. They are know for leaks also. You sure it isn't that leaking. There is an update kit for the pass through connector. As far as between the two I am not sure.

[Lt.Del]

Yeah, it does have a large black round plug on the drivers side---and I am pretty sure it is leaking from the pan---I started it up yesterday and immediately dropped down to look up under the trans and the fluid was really pouring and dripping onto the bell housing.

I think I figured out that I have a 4L80E according to the Auto Zone website---a 17 bolt pan.

[eventhorizon66]

Here, this ought to help you as far as identification goes.  Automatic transmission identification page  Looks like you're right - if its got 17 bolts its a 4L80E.

[Lt.Del]

I am puzzled...I assumed it had 17 bolt holes because it looked like the pan from a 4L80E...but,upon counting, i have only 16 holes, but the pan still looks like a 4L80E pan.  I don't know....

[eventhorizon66]

Try measuring the case length to confirm what it is.  Or notice how the trans mount of the 4L60E is located on the main case while the 4L80E's is on the tail shaft housing.

Also, using the RPO, I found on another page that the MT1 means 4L80E.  A 4L60E would be an M30.  Here's the page: Truck engine codes.  Maybe you mis-counted the bolt holes?

[VileZambonie]

4L80E and the R is 2WD V is 4WD

[Lt.Del]

Thanks a lot for the replies.  I counted the holes for the pan 6 different times, always getting 16 holes.
The mount is kind of on the casing, because I will have to remove the mount to get to about three of the pan bolts---such a pain.

So, my rpo code says MT1, but, man, unless something is wrong, it does have 16 holes.

The only thing I can think of is either the info is wrong on the pages or the trans may have been swapped at some point----but still the pan resembles the 4L80E, except for the hole count.

[VileZambonie]

You should have 17 bolt holes. Can you take a pic of the bottom of the pan so we can see what's different?

[eventhorizon66]

No way the mount should be so close to the rear pan bolts if it's a 4L80E (sounding more and more like a 4L60E).  And if it does turn out that some knuckle-head swapped a 4L60E in place of the 4L80E, you don't have to remove the trans mount to get to the rear three bolts, it just takes a little dexterity, a closed-end wrench, and some patience.  I know because I've done it.

[Lt.Del]

I'll get some more pics in the next day or three.  I do have this one showing the tranny mount is right under a few of the pan bolts.







Mason plays Notre Dame Thurs

[VileZambonie]

All you have to do is unbolt the mount from the crossmember and jack up the t-case to gain access to the bolts.

[Lt.Del]

thanks vile, that helps...i have little experience working on a 4x4. I'm going to take some measurements and take some more pics to try to figure out the type of tranny.

I appreciate all the help here.






12 seed GMU vs. 5 seed Notre Dame Thurs.
March Madness

[eventhorizon66]

Oh, sorry, I forgot when I advised you on getting to those bolts and location of the trans mount, that you had a tranfer case where the tail shaft housing would normally be.  Wups, well you should be listening to Vile, not me, anyways.

[DnStClr]

The 4l80e is going to be  bigger than a 4l60e and it has 32 spline output shaft while the 4l60e has a 27 spline output shaft.
While the 4l60e can be swapped over for a 700R4 because it replaces the 700R4, the bigger 4l80e can't be directly swapped. It's longer and the driveshaft has to be shortened 3 1/4" to fit. so the crossmember has to be moved too.
 The oal of the 4l80E is 31". It's used in the 3/4 ton and one ton applications.