99 front differential in a 97 - The 1947 - Present Chevrolet & GMC Truck Message Board Network

pwdcougar · 12-03-2023, 08:07 PM

Anyone here put a 99 front differential in a 97?

b454rat · 12-05-2023, 06:39 PM

Why? There isn't a difference. In less your talking the NBS diff....

**special-K** · 12-06-2023, 07:11 AM

Should be a straight swap

pwdcougar · 12-06-2023, 10:01 AM

The issue is that the 97 has a pigtail for the actuator and a pigtail for the 4wd engagement light. The 99 diff uses the mechanical actuator and has only one pigtail. Physically the differential bolts right up.

It took a few days of research and modifications to the wiring harness but I’ve got it sorted out.

**special-K** · 12-07-2023, 09:08 AM

Is the mechanical actuator aftermarket? Glad you worked it out

pwdcougar · 12-07-2023, 01:18 PM

Quote:

Originally Posted by special-K

Is the mechanical actuator aftermarket? Glad you worked it out

The mechanical actuator was stock 99 and up for this particular front differential. Chevy got complaints about the thermal actuators slow engagement in cold weather. To upgrade to the new style there is a service bulletin and a wiring harness from GM.

**special-K** · 12-08-2023, 08:37 AM

I know about the slow actuators, the reason for the aftermarket conversions. I didn't realize GM changed that in the last GMT400s. Took them long enough. Obviously only concerned with the next trucks being better in that function.

b454rat · 12-08-2023, 07:59 PM

They had to make them quicker for the Autocrap t-cases. When in 4wd Auto, the t-case is in 2wd, but soon as it senses rear wheel spin, in engages the actuator instantly. Sorta. Best thing I did, was convert to an NP241.

12-03-2023, 08:07 PM	#1
pwdcougar Registered User Join Date: Oct 2013 Location: New Jersey Posts: 1,302	99 front differential in a 97 Anyone here put a 99 front differential in a 97? __________________ "You know that little thing in your head that keeps you from saying things you shouldn't? Yeah well, I don't have one of those" 1969 Mercury Cougar Standard 4 speed 1969 Mercury Cougar XR7 convertible 1970 4WD Chevrolet Suburban 1997 4WD Chevrolet Silverado Extended Cab Short Bed (purchased new January 1997)

12-05-2023, 06:39 PM	#2
b454rat Senior Member Join Date: May 2004 Location: Binghamton, NY Posts: 3,454	Re: 99 front differential in a 97 Why? There isn't a difference. In less your talking the NBS diff.... __________________ 2000 GMC CCSB 454/4L80 6” lift SAS 1999 Chevy CCSB 454/NV4500 6” lift 1999 GMC Yukon 350/4L60 4" SAS

12-06-2023, 07:11 AM	#3
special-K Special Order Join Date: Nov 2004 Location: Mt Airy, MD Posts: 85,862	Re: 99 front differential in a 97 Should be a straight swap __________________ "BUILDING A BETTER WAY TO SERVE THE USA"......67/72......"The New Breed" GMC '67 C1500 Wideside Super Custom SWB: 327/M22/3.42 posi.........."The '67" (project) GMC '72 K2500 Wideside Sierra Custom Camper: 350/TH350/4.10 Power-Lok..."The '72" (rolling) Tim "Don't call me a redneck. I'm a rough cut country gentleman" R.I.P. ~ East Side Low Life ~ El Jay ~ 72BLUZ ~ Fasteddie69 ~ Ron586 ~ 67ChevyRedneck ~ Grumpy Old Man ~

12-06-2023, 10:01 AM	#4
pwdcougar Registered User Join Date: Oct 2013 Location: New Jersey Posts: 1,302	Re: 99 front differential in a 97 The issue is that the 97 has a pigtail for the actuator and a pigtail for the 4wd engagement light. The 99 diff uses the mechanical actuator and has only one pigtail. Physically the differential bolts right up. It took a few days of research and modifications to the wiring harness but I’ve got it sorted out. __________________ "You know that little thing in your head that keeps you from saying things you shouldn't? Yeah well, I don't have one of those" 1969 Mercury Cougar Standard 4 speed 1969 Mercury Cougar XR7 convertible 1970 4WD Chevrolet Suburban 1997 4WD Chevrolet Silverado Extended Cab Short Bed (purchased new January 1997)

12-07-2023, 09:08 AM	#5
special-K Special Order Join Date: Nov 2004 Location: Mt Airy, MD Posts: 85,862	Re: 99 front differential in a 97 Is the mechanical actuator aftermarket? Glad you worked it out __________________ "BUILDING A BETTER WAY TO SERVE THE USA"......67/72......"The New Breed" GMC '67 C1500 Wideside Super Custom SWB: 327/M22/3.42 posi.........."The '67" (project) GMC '72 K2500 Wideside Sierra Custom Camper: 350/TH350/4.10 Power-Lok..."The '72" (rolling) Tim "Don't call me a redneck. I'm a rough cut country gentleman" R.I.P. ~ East Side Low Life ~ El Jay ~ 72BLUZ ~ Fasteddie69 ~ Ron586 ~ 67ChevyRedneck ~ Grumpy Old Man ~

12-08-2023, 08:37 AM	#7
special-K Special Order Join Date: Nov 2004 Location: Mt Airy, MD Posts: 85,862	Re: 99 front differential in a 97 I know about the slow actuators, the reason for the aftermarket conversions. I didn't realize GM changed that in the last GMT400s. Took them long enough. Obviously only concerned with the next trucks being better in that function. __________________ "BUILDING A BETTER WAY TO SERVE THE USA"......67/72......"The New Breed" GMC '67 C1500 Wideside Super Custom SWB: 327/M22/3.42 posi.........."The '67" (project) GMC '72 K2500 Wideside Sierra Custom Camper: 350/TH350/4.10 Power-Lok..."The '72" (rolling) Tim "Don't call me a redneck. I'm a rough cut country gentleman" R.I.P. ~ East Side Low Life ~ El Jay ~ 72BLUZ ~ Fasteddie69 ~ Ron586 ~ 67ChevyRedneck ~ Grumpy Old Man ~

12-08-2023, 07:59 PM	#8
b454rat Senior Member Join Date: May 2004 Location: Binghamton, NY Posts: 3,454	Re: 99 front differential in a 97 They had to make them quicker for the Autocrap t-cases. When in 4wd Auto, the t-case is in 2wd, but soon as it senses rear wheel spin, in engages the actuator instantly. Sorta. Best thing I did, was convert to an NP241. __________________ 2000 GMC CCSB 454/4L80 6” lift SAS 1999 Chevy CCSB 454/NV4500 6” lift 1999 GMC Yukon 350/4L60 4" SAS



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