The stock 4.3 transmission is typically "worn-out" by the time most people want to swap engines. It may last for a while, but it will quit working, usually at the worst time.
If you are going with the 4.3 transmission, pull it out and have it rebuilt with performance parts.
LS-based 4.8 and 5.3 truck engines are available with either a 4L60E, 4L65E or 4L70E transmissions.
The LQ4 and LQ9 engines are available with either a 4L65E or 4L80E transmission. For S10 conversions, the 4L60-70 series transmissions are the easiest. The 6-liter TBSS engine comes with the 4L70E transmission.
F-Body engines have the 4L60E trans.
These transmissions have a torque rating of approximately 350-400 ftlbs. Keep this in mind once performance modifications
begin with the engine.
These transmissions require a transmission fluid cooler. This can range from an in-radiator (simplest) to an external aftermarket unit.
Some swappers use a cooler with a built-in electric fan, controlled by a temperature switch.
Remember, temperature is the killer of automatic transmissions. A cooler is manditory.
Common and prudent modifications to these transmissions include mild shift kits and Corvette servos.
Performance modifications to the engine may require high performance build-ups and/or a performance transmission.
(Phoenix transmissions in Weatherford TX, Monster transmissions, FLT Transmissions, and many others. Research this independantly)
For a stock drivetrain, it's easiest and most cost effective to retain the stock torque converter.
For performance applications, a higher stall converter may be appropriate for your drivetrain/useage combination. Research this independantly also.
New Torque Converter installation:
1. Flush out transmission oil cooler and lines. Add a quart of new transmission fluid to the torque converter. Using the aid of a helper, stand the transmission on the tail shaft and carefully install the torque converter onto the transmission. Spin the torque converter and listen for 3 distinct clicks as it drops into the transmission. The following are measurements you can make to insure the torque converter is all the way in the transmission:
4L60E = 1.125" from bellhousing to converter pads.
GM 4L80E = 1.030" from bellhousing to converter pads.
Distance may vary +/- .050".
2. Remove any debris in the crankshaft pilot hole and lubricate. Clean and lubricate the dowel pins. Check to see that dowel pins will be in the transmission bellhousing by more than .250".
3. Mount transmission to the back of the engine block making sure the bellhousing fits squarely against the block. If it does not, find out why! Is there something between the bellhousing and block or has the torque converter slipped out of the transmission? DO NOT PULL UP THE BELLHOUSING TO THE BLOCK USING THE BELLHOUSING BOLTS!!!!
4. After the transmission bellhousing bolts are tightened, check to see if the torque converter will turn by hand. Push the torque converter back into the transmission as far as it will go. Using feeler gauges or calipers measure the gap between the flexplate converter mounting pad and the torque converter mounting pad. If gap distance is between .060" and .187" it is OK to bolt up the torque converter using RED Loctite on the bolts. If the gap is greater than .187" install a .060" flat washer between the torque converter and flexplate.
5. Finish installing the cross member, exhaust, driveshaft, etc. Add 5 quarts of good quality transmission fluid. Start the engine and immediately add 2 more quarts. Check the fluid and finish filling the transmission to proper level.
The 4L80e Transmission is another option, but it does require additional modifications to fit.
LS-x trans to LS-x engine, no spacers needed
An older type trans to LS-x, either use a spacer OR long crank 6.0 (early, 99-01) with the flat flexplate, put the spacer between the flexplate and crank.
If it's a dished plate, put the spacer on after the flexplate.
Unless a custom built converter is used, keep the older type TCs with the older trans(s10 TC is for older type trans), TRAILblazer TC(I6) is for LSx trans
Dished Flexplate with Spacer:
There are a couple of variants of this transmission.
The LS Camaro
When installing the engine/tranny be sure to either trim or massage the lip from the firewall to the tunnel. It clears fine without trimming but makes clutch changes nearly impossible. You cannot access the top bell housing bolts with the lip in place.
A speed bleeder is also a must IMO. If you do a clutch change or have the typical loss of pedal pressure that is common in the T-56 hydraulics, it is nearly impossible to bleed the system without this. The bleeder bolt has very little clearance to get a wrench on it.
Also a great idea to replace the hydraulic fluid with a non-synthetic racing brake fluid to help keep the fluid from boiling during with spirited driving. (yes this even happens on the new C6Z06
The stock S-10 hydraulics are sufficient. This includes the master cylinder, line, fittings, and pedal. (I know some have used the stock 4.3 slave cylinder). I recommend changing the slave cylinder since this was an OEM issue and still is.
You can use the stock 4.3 5-speed tranny crossmember (modified), stock auto crossmember (modified) and/or BRP makes a T-56 crossmember.
It may be necessary to patch the existing shifter hole in the transmission tunnel and make a new one aprox. 4" to 6" back.
It's possible to use the stock F-body shifter, boot, knob.
A stock Blazer '95 to '97 console, that was originally a column shift truck, can be used. Cut out the the bottom of the cup holder and the insert. Wrap the stock F-body shifter boot around the insert and glue (or rivits and/glue.) This works really well and makes for easy access to the shifter mounting bolts.
On an extended cab truck, the 2-piece driveshaft will need to be shortened approximately 1.5" (measure twice and cut once!) Always install new joints, new carrier bearing, and have the shaft balanced.
T-56 with a GTO shifter knob in a '95-'97 Blazer console:
T-56 with a F-body shifter in a '98-'05 Blazer Console
(Nice Gen 3 Firebird seats!)
(Thanks for the pics Petro)
The newer 6L80e/6L90e transmissions have a larger physical casing and will not fit in the transmission tunnel without modification. In addition, only a couple of harness suppliers (Street & Performance, MAST, Speartech, etc) have products which will operate these transmissions. From a practical standpoint, these transmissions are not good solutions for S10 Conversions yet.
The Pontiac G8 with the 6L80E transmission uses a transmission fluid pan which is 3/4" shorter than the Cadillac version. This will help with ground clearance.
Gen I Automatics Behind Gen III/IV Engines
(Everything you wanted to know about mounting transmissions to LS engines: http://www.carcraft.com/techarticles/ccrp_0810_engine_transmission_swap_gen_3/torque_specs.html)
The same mismatch between the 0.400-inch-shorter crank flange position relative to the bellhousing is what makes matching up a typical TH350/TH400/200-4R, a 700-R4 or a "non-LS-engine" 4L60e to a Gen III/IV engine a bit different. The beauty of this swap is most of the mismatch situations can be solved with the use of a simple steel adapter.
GM actually faced an identical situation when bolting the 4L80E automatics behind 5.3L and 6.0L engines in larger trucks. The 4L80E automatic is basically a Gen I-style automatic, which required an adapter.
To compensate, GM created a simple steel spacer (GM PN 12563532 and 6 new flexplate bolts PN 12563533) that bolts on the Gen III/IV crank flange and combines with a flat flexplate. All this information is published in the GM Performance Parts LS1 engine swapping performance pamphlet.
The adapter and flat flexplate, along with longer metric bolts, are intended to be used together and will allow you to bolt any Powerglide, TH350, TH400, 700-R4, or 200-4R automatic to a Gen III/IV version engine. The part numbers for these pieces can be found in the parts list at the end of this story.
Unfortunately, there are also a few minor details that need to be addressed. For example, the flat flexplate used with the spacer is designed for a 300mm (11.8-inch) bolt pattern, while most Gen I transmission torque converters use an 11.7-inch bolt pattern. The difference between these two bolt patterns ends up being roughly around 1/8 inch. The 300mm bolt pattern holes can be carefully elongated with a file or die grinder to accommodate the smaller Gen I converter bolt pattern.
TCI makes a similar package that offers an SFI-approved performance flexplate and includes the adapter and bolts, all for an excellent price through SDPC. This flexplate bolts up to the Gen III/IV crankshaft and also features a dual converter bolt pattern that will accommodate both the early and metric torque converter bolt patterns, so no modifications are necessary.
FASTENER..............(ft-lb, unless specified)
Flywheel bolts.................15 (1st pass)
....................................37 (2nd pass)
....................................74 (final pass)
Pressure plate bolts, ARP...35
You can determine the type of transmission from the 4 large alpha-numeric characters on the transmission's ID tag. The 1st position is the Year Model of the transmission. The 2nd and 3rd positions determine the model of the transmission (4L60E) The 4th position determines what transmission family it belongs to. To the right is a sample ID Tag. ID Tag styles vary.
1. Model Year
2. Model Code
3. Transmission Family
4. Transmission Assembly Number
5. Julian Date
6. Sequential Serial Number
7. Source Code
8. Broadcast Code
9. Bar Code
10. Transmission I.D.
Below are some of the Transmission Broadcast Codes that are common.
Only Position 2/3/4 are listed because the 1st position changes with the year.
The number of Connector Pins is also listed.
2/3/4 Broadcast Code___Transmission Model__# of Connector Pins