Write-Up: 4T80e Transmission Install

got a core 4t65 from the junkyard.
it got a complete overhaul with:
hardened 4th gear hub
raybestos blue clutch pack
trans go shift kit
high energy green forward band
new planet gear
master overhaul kit with all new solenoids
topped off with 245mm torque convertor with a 2500 stall

all the wiring is already run from the 4t80 project. hopefully I'll have this installed and tuned within a few days.

btw, there is a shift kit for the 4t60 and the clutch pack said that it would work in the 4t60 as well. So it may be possible to build it up some, but I didn't feel it would be strong enough for my current and future mods.

HD diff?

deekster_caddy wrote:

HD diff?

im not sure. the trans was supposed to be out of a 99 grand prix. Im assuming it was a GT and not a GTP, simply cause GTP's were alot less common.

now Im pretty sure my 4t60 wasnt HD differential. The axles look the same.

I don't suppose the case has any identifying numbers/letters, does it?

Off the top of my head, for H.D. look for MN7, 8FCB, 8FDB, or 8XAB...


I never thought of it before: Do the H.D. units use shorter half-shafts on the right?

well its in.

had to use gearing settings from a Grand prix GT bin to get rid of the incorrect gear ratio DTC. kept going into limp mode. 3.29 fdr i think in my trans vs. the 2.93 i had before.

cant seem to get TCC to lock (no 4th gear). think its a tuning problem.

still not as tough as a 4t80, but doesnt slip like my 4t60e.

Glad to see you're moving forward.

Your car has been down for awhile hasn't it?

dreww wrote:

well its in.

had to use gearing settings from a Grand prix GT bin to get rid of the incorrect gear ratio DTC. kept going into limp mode. 3.29 fdr i think in my trans vs. the 2.93 i had before.

Plus, they used (at least) two different sets of chain gears as well as differential gears, so there are Final Drive Ratios and Overall Drive Ratios... You might have 3.29 final drive gears with an overall ratio of 3.05. Got any radar-signs you can use to check the speedo now?

Karma wrote:

Glad to see you're moving forward.

Your car has been down for awhile hasn't it?

Yes, 18 months.

Eldo wrote:

dreww wrote:

well its in.

had to use gearing settings from a Grand prix GT bin to get rid of the incorrect gear ratio DTC. kept going into limp mode. 3.29 fdr i think in my trans vs. the 2.93 i had before.

Plus, they used (at least) two different sets of chain gears as well as differential gears, so there are Final Drive Ratios and Overall Drive Ratios... You might have 3.29 final drive gears with an overall ratio of 3.05. Got any radar-signs you can use to check the speedo now?

thx for confusing me more.

saga continues...
bought a new range switch to try to get 4th gear. while i got the shifter display on the dash to show overdrive, i never got 4th.

but that doesnt matter now, as i went to downshift from 2nd to 1st on a testdrive, something happened. the result, shattered passenger side axle.

consensus is the stall convertor built up torque as it 'stalled' and BAM. gonna replace with HD diff and axle.

ok, updates - but nothing positive. This piece of shit is driving me nuts

pulled out the 4t65 trans. It was leaking and no 4th gear. Apparently when the stock non HD axle blew out it cracked the transmissions housing...almost in two. The crazy thing is that the trans still drives!

The crack goes from inside next to the input shaft all the way to the outer edge of the drives side axle. No JB Weld is gonna fix this. So we need a new core. Also the stock input shaft is a little stripped but the 2500 stall convertor seems to be fine. So the fix will include an 4340 input shaft. Although a full rebuilt isn't quite needed, it must be done just to transfer the guts of the current 4t65 with broken housing to a new core. Also the rear trans mount bracket was stripped out of the trans housing so a new housing is pretty much a no brainer.

Anyone ever seen a trans housing crack yet the trans still worked?

pics below:

Mine cracked in a different place, still worked but leaked fluid all over the place... as long as it has enough pressure it will keep working. Crazy huh?

I've heard of it before - cracked case and still driving. I don't like the fact that the case is cracking before other hard parts snap though. The splines on the input shaft wearing out is pretty much a given if you're running an aftermarket stall converter with the stock input shaft. They usually have hardened splines hence why a hardened input shaft upgrade pretty much requires an upgraded torque converter with it.

deekster_caddy wrote:

Mine cracked in a different place, still worked but leaked fluid all over the place... as long as it has enough pressure it will keep working. Crazy huh?

was it your stock trans than broke? or your built trans?

turtleman wrote:

I've heard of it before - cracked case and still driving. I don't like the fact that the case is cracking before other hard parts snap though. The splines on the input shaft wearing out is pretty much a given if you're running an aftermarket stall converter with the stock input shaft.

yea makes me wonder whats to keep another case from cracking? Not like I can pickup new shells for a few bucks.

dreww wrote:

deekster_caddy wrote:

Mine cracked in a different place, still worked but leaked fluid all over the place... as long as it has enough pressure it will keep working. Crazy huh?

was it your stock trans than broke? or your built trans?

umm, it was my built trans, but was having rear mount issues and cracked it around the mount. (wrong case...) swapped all the buit parts into my correct case and didn't have any probems after that.

deekster_caddy wrote:

dreww wrote:

deekster_caddy wrote:

Mine cracked in a different place, still worked but leaked fluid all over the place... as long as it has enough pressure it will keep working. Crazy huh?

was it your stock trans than broke? or your built trans?

umm, it was my built trans, but was having rear mount issues and cracked it around the mount. (wrong case...) swapped all the buit parts into my correct case and didn't have any probems after that.

thats exactly what happened to me. We didnt have the back mount bolted in when we blew it out. We had a bracket rigged in there but all the bolts snapped off in the trans housing and it fell out when I barely put my foot down. Both of my housings have the 3 bolts holes but they dont bolt up to the rear trans mounting bracket very well.

What did you do to fix that problem? Custom fabbed the rear bracket? I looked at half a dozen 4t65's at the junkyard and they all had the same 3 bolt hole layout.

this is the core we got for $50. Were gonna gut it next week for learning purposes (cause we dont gotta put it back together) and take the core and blown trans to a guy for an internals swap.

Dreww what happened?

Wow, 5 years later... I missed the followup on this thread. What I ended up doing was bringing both transmissions to my trans shop and they rebuilt the Riv trans with all the good parts from the cracked one, plus a few additional pieces (hardened input shaft etc). I guess they did a good job because that build is still holding up almost 200,000 later with a number of 1/4 passes and many many many highway miles.

deekster_caddy wrote:

Wow, 5 years later... I missed the followup on this thread. What I ended up doing was bringing both transmissions to my trans shop and they rebuilt the Riv trans with all the good parts from the cracked one, plus a few additional pieces (hardened input shaft etc). I guess they did a good job because that build is still holding up almost 200,000 later with a number of 1/4 passes and many many many highway miles.

Deek, you put a 4T80e in your Riv?

Oh, sorry. No, we used a 4T65. I saw the last question was directed at me but not the thread title.

deekster_caddy wrote:

Oh, sorry. No, we used a 4T65. I saw the last question was directed at me but not the thread title.

Ah, gotcha. I wonder if dreww is still around and if the 4t80 ever worked out for him.

I did some research and it looks like a bitch to squeeze in and GMR chain may be more rare than eibach lowering springs.

I may have to settle for a safe 400whp end game..

Go peek around the Grand Prix forums. There's some people messing with them there.