Northstar Engines and System Technical Discussion Discussion, 4T80E 3.11 to 3.71 swap in Cadillac Engine Technical Discussion; Originally Posted by Maxb49
Is there a significant improvement in acceleration?
Yes, on the order of .3 to .5 tenths ...
I am well aware that the 99 and prior needs the correct trans calibration to shift correctly. The 00+ is much easiers to swap that part of the program so now I have to work that out of my 99 program. It bounces of the revlimiter about 10 times before it will shift
Could this swap be done with from 3.11 to 3.71 without a computer modification? I have a 94 so I OBDI, I'm just thinking an inline resistor of some sort could modulate the signal to the computer and fool it, though I really dont know how the signal works. I have my trans apart and the differential at hand, I'm just not sure how I could get the computer to co-op with me. Any ideas? or electronics wizards?
From what I have experienced you will need to change the PCM program on 93 to 99 cars. the 00 to 03 may not require it. I am not sure.
Originally Posted by BlackCaddy87
What all is needed to do this swap and how much money would it take?
You need 3 parts + fluid
Carrier #24205233 List $659.60 Trademotion.com $379.73
Sun gear #08678825 List $144.56 Trademotion.com $83.22
The Extension Case to Case Seal $??
Fluid about 6 quarts
96 to 99 PCM tune for this $200
$700 or so. New
Yep, been running around with the gears for well over a year now, threw in a stall while we were doing it. Love it!!! Should have been the first thing I did was get rid of those 3.11's. I personally think the 3.71's work real nice with the "base" cams. Why they didn't come from the factory that way, I'll never understand, they do stick the higher gear with the base N* finally but only in Pontiacs, go figure. God the Corsa's cackle on the highway from the extra rpms, I love that too!
I Gonna be doing this swap, to wake up my SLS, MY question are the indicated tools Necessary, I don't see them refered to in the Procedure?
Also I have a 2001 STS Computer, since this swap is being done with a 2001 SLS, Is it better to swap the computers to have the Shift points match up but throw the fuel/timing tabels off or is it better to leave the SLS PCM and have the shift points off?
Originally Posted by AJxtcman
2000 to 2005 Devilles and Sevilles.
Case Extension Replacement
• J 8001 Dial Indicator Set
• J 25025-7A Dial Indicator Mounting Post
• J 28585 Snap Ring Remover
Raise and support the vehicle. Refer to Lifting and Jacking the Vehicle .
Support the vehicle with safety stands.
Remove the right drive axle. Refer to Wheel Drive Shaft Replacement .
Remove the wiring harness.
Remove the vehicle speed sensor. Refer to Vehicle Speed Sensor Replacement .
Remove the right transmission to engine brace. Refer to Transaxle Brace Replacement .
Remove the ground wire from the case.
Remove the following parts from the case extension:
• Five 13 mm bolts (128, 129)
• One 15 mm stud (127)
Remove the case extension (134) and the seal (126).
Remove the roller thrust bearing (132) and the selective washer (133).
Remove the 8 mm scavenge tube bolt.
Remove the scavenge tube by prying on the differential.
Remove the scavenge tube seal.
Final Drive Assembly Replacement
Remove the case extension. Refer to Case Extension Replacement .
Rotate the manual shaft (16) counterclockwise in order to place the transaxle in Park (P) and prevent the differential from rotating.
Remove the 4 bolts (119) from the differential housing to transaxle case.
Remove the differential carrier.
Push on the output shaft in order to expose the left side differential gear snap ring. Remove the left side differential gear to output shaft snap ring (56).
Remove the differential side gear (118) and thrust washer (117).
Remove the final drive carrier (100) and the thrust bearing.
Remove the final drive sun gear (121).
Install the sun gear (121) with the bushing and the seal side facing differential.
Install the final drive carrier (100). Turn the unit until it meshes with the sun gear and the internal gear teeth.
Install the left thrush washer (117).
Install the left differential side gear (118).
Install the snap ring (56).
Use the manual shaft to place the transaxle in park.
This will lock up the final drive unit. The actuator rod will move up.
Notice: Use the correct fastener in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use paints, lubricants, or corrosion inhibitors on fasteners or fastener joint surfaces unless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems.
Install the differential housing and the four bolts (119). Hand tighten, using a star pattern.
Tighten the bolts to 76 N·m (56 lb ft).
Install the case extension. Refer to Case Extension Replacement .