INTENSE™ Street/Strip Performance Shift Pak®

INTENSE™ Street/Strip Performance Shift Pak®


Part Number: TSP-651

Shipping Weight: 3.00 pounds

5 out of 55 out of 55 out of 55 out of 55 out of 5 5 Customer reviews
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  • 2000-Current Impala
  • 1998-current Grand Prix GT
  • 1998-current Monte Carlo
  • 1998-current other applications using the 4T65E (non -HD) transaxle
  • 1997-current Grand Prix GTP
  • 1997-current Regal GS
  • 1997-current Bonneville SSEi
  • 1997-current other applications using the 4T65E-HD transaxle
The INTENSE™ Street/Strip Performance Shift Pak® is designed to give you crisp shifts under light to medium throttle positions, and very firm shifts at wide open throttle. It is not designed to rip your dashboard out, break your input shaft or destroy your transaxle drive chain.

The INTENSE™ Street/Strip Performance Shift Pak® is installed by removing the transaxle pan, then the accumulator cover. The accumulator housing contains the 1-2 and 2-3 pistons that control the rate at which fluid pressure gets applied to the clutch packs during upshifts and downshifts. Our kit contains custom springs and spacers to create the ideal shifts for a mix of street and strip use. Shorter shift cycle times mean less time when the PCM retards ignition timing during each shift to protect the transaxle.

Shortening the shift times serves to increase clutch life, due to less slippage between gears. Less slippage equates to less heat, and less heat can extend overall transaxle life.

There are two basic settings, depending on whether you have a 245 mm. (stock in 4T65E transaxles) or 258 mm. (stock in 4T65E-HD transaxles) torque converter. This kit is by far the most comprehensive performance shift pak on the market for our transaxles. Every kit includes:
  • 5 custom accumulator piston springs
  • 3 custom flat spacers
  • 8 custom cylindrical spacers
  • sandpaper to smooth accumulator gasket surface for improved mating
  • new accumulator gasket
  • abrasive pad to scuff accumulator bores for increased oil on bore walls
  • 2 new piston seals
  • new transaxle filter
  • transmission assembly lubricant
  • extremely detailed installation instructions with full color images explaining how to inspect your transaxle pan contents, and properly prepare the accumulator cover, accumulator pistons and piston pins.

- Unfortunately this kit will NOT fit 4T60E transaxles.

- Installation should average one to two hours depending on your skill level.

- No special tools are required other than an inch-pound torque wrench.


Transaxle components fail - especially in cars modified for increased power outputs. Transaxle failures occur in completely stock transaxles and ones with performance shift paks too. Your purchase and installation of this product constitutes your acceptance of any and all liability with regard to this product. INTENSE Enterprises, Inc. will not be held liable for any transaxle or other damage that occurs due to the installation, misinstallation or use of this product.

Average Customer Review: 5 out of 55 out of 55 out of 55 out of 55 out of 5 Based on 5 Reviews

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5 out of 55 out of 55 out of 55 out of 55 out of 5 Good kit

Joe Fair (Columbus, IN) 11.26.2021

Just installed this in a 2011 Buick Lucerne 3.9. It took some time to get it all done, and the three hard lines were a pain to get all right and the mounting screws lined up. Obviously, that's not a product problem. The parts all went together right, and installed seven quarts of trans oil afterwards. It's still a tick low, but nothing that I'm going to worry about, probably a quarter quart. It does exactly what it claims. Light throttle shifts ARE a little firmer, and wide open very firm. Overall, the instructions were excellent, and the parts installed exactly as expected. If you're using this hardware to firm up a shift instead of PCM tuning (not an option for the Buick), I think you'll like the results.

5 out of 55 out of 55 out of 55 out of 55 out of 5 Buick Century (1811 hardshift)

William Blackburn (Cynthiana, KY) 4.21.2019

I had a 2000 Buick Century. Great car but had the 1811 hardshift sickness. Had it at a transmission shop 9 times, transmission rebuilt, oil cooler, new computer, 2nd rebuilt transmission, still hardshift. Bought a 2004 Buick Century, had the "Intense" shift kit installed 8 months after I bought it for it would also go into code 1811 hardshift occasionally. I love this car even more now. It has NOT once had hardshift. It has a nice shift now, just perfect. This is one company you can trust. Great people, great products. Thank You!!

5 out of 55 out of 55 out of 55 out of 55 out of 5 2006 Impala LTZ

Branden (Hopkins, MN) 3.29.2013

I just wanted to add a little zip to the car and this kit is PERFECT. Much firmer shifts under light to medium throttle as it says, much less "slack" in the transmission under normal driving conditions. When under full throttle she performs beautifully....I even get a little chirp into 2nd! I would recommend this kit to anyone!

5 out of 55 out of 55 out of 55 out of 55 out of 5 GREAT KIT

Pete (Toronto, ON) 4.22.2012

I installed this kit because of a steady code of 1811.Slipping shifts betweem 1-2 and 2-3. Now it shifts BANG on! Under heavy load it clicks in nice and tight.The Alternative was to rip apart the drivers side cover and remove the axle and replace the pressure valve.Easy to install the tranny shop really liked the looks of the kit with the good instructions. Thanks Again Pete Canada

5 out of 55 out of 55 out of 55 out of 55 out of 5 2000 Pontiac Bonneville SSEI hard shifting

Barry (Kirkwood, PA) 3.12.2012

Your shift kit resolved my hard shifting problem after the transmission warmed up. It was easy to install and the car shifts fine.

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