Specifications Comparison: 2021 GMC Sierra 3500 vs 2015 GMC Sierra 3500

Headroom

Trim	Eng.	Drive train	1st Row Headroom (in)	2nd Row Headroom (in)
HD Crew Cab	6.6L V8	RWD	43	40
HD Crew Cab	6.6L V8	RWD	43	40
HD Crew Cab	6.6L V8	4WD	43	40
HD Crew Cab	6.6L V8	4WD	43	40
HD Crew Cab AT4	6.6L V8	4WD	43	40
HD Crew Cab AT4	6.6L V8	4WD	43	40
HD Crew Cab Denali	6.6L V8	4WD	43	40
HD Crew Cab Denali	6.6L V8	4WD	43	40
HD Crew Cab SLE	6.6L V8	RWD	43	40
HD Crew Cab SLE	6.6L V8	RWD	43	40
HD Crew Cab SLE	6.6L V8	4WD	43	40
HD Crew Cab SLE	6.6L V8	4WD	43	40
HD Crew Cab SLT	6.6L V8	RWD	43	40
HD Crew Cab SLT	6.6L V8	RWD	43	40
HD Crew Cab SLT	6.6L V8	4WD	43	40
HD Crew Cab SLT	6.6L V8	4WD	43	40
HD Extended Cab	6.6L V8	RWD	43	39
HD Extended Cab	6.6L V8	RWD	43	39
HD Extended Cab	6.6L V8	4WD	43	39
HD Extended Cab	6.6L V8	4WD	43	39
HD Extended Cab SLE	6.6L V8	RWD	43	39
HD Extended Cab SLE	6.6L V8	RWD	43	39
HD Extended Cab SLE	6.6L V8	4WD	43	39
HD Extended Cab SLE	6.6L V8	4WD	43	39
HD Regular Cab	6.6L V8	RWD	43
HD Regular Cab	6.6L V8	RWD	43
HD Regular Cab	6.6L V8	4WD	43
HD Regular Cab	6.6L V8	4WD	43
HD Regular Cab SLE	6.6L V8	RWD	43
HD Regular Cab SLE	6.6L V8	RWD	43
HD Regular Cab SLE	6.6L V8	4WD	43
HD Regular Cab SLE	6.6L V8	4WD	43

Trim	Eng.	Drive train	1st Row Headroom (in)	2nd Row Headroom (in)
HD 3500 Crew Cab Denali	6.0L V8	RWD	42.8	40.5
HD 3500 Crew Cab Denali	6.0L V8	4WD	42.8	40.5
HD 3500 Crew Cab SLE	6.0L V8	RWD	42.8	40.5
HD 3500 Crew Cab SLE	6.0L V8	4WD	42.8	40.5
HD 3500 Crew Cab SLT	6.0L V8	RWD	42.8	40.5
HD 3500 Crew Cab SLT	6.0L V8	4WD	42.8	40.5
HD 3500 Crew Cab Work	6.0L V8	RWD	42.8	40.5
HD 3500 Crew Cab Work	6.0L V8	4WD	42.8	40.5
HD 3500 Extended Cab SLE	6.0L V8	RWD	42.8	38.7
HD 3500 Extended Cab SLE	6.0L V8	4WD	42.8	38.7
HD 3500 Extended Cab SLT	6.0L V8	RWD	42.8	38.7
HD 3500 Extended Cab SLT	6.0L V8	4WD	42.8	38.7
HD 3500 Extended Cab Work	6.0L V8	RWD	42.8	38.7
HD 3500 Extended Cab Work	6.0L V8	4WD	42.8	38.7
HD 3500 Regular Cab SLE	6.0L V8	RWD	42.8
HD 3500 Regular Cab SLE	6.0L V8	4WD	42.4
HD 3500 Regular Cab Work	6.0L V8	RWD	42.8
HD 3500 Regular Cab Work	6.0L V8	4WD	42.4

Trim	Eng.	Drive train	1st Row Headroom (cm)	2nd Row Headroom (cm)
HD Crew Cab	6.6L V8	RWD	109	101
HD Crew Cab	6.6L V8	RWD	109	101
HD Crew Cab	6.6L V8	4WD	109	101
HD Crew Cab	6.6L V8	4WD	109	101
HD Crew Cab AT4	6.6L V8	4WD	109	101
HD Crew Cab AT4	6.6L V8	4WD	109	101
HD Crew Cab Denali	6.6L V8	4WD	109	101
HD Crew Cab Denali	6.6L V8	4WD	109	101
HD Crew Cab SLE	6.6L V8	RWD	109	101
HD Crew Cab SLE	6.6L V8	RWD	109	101
HD Crew Cab SLE	6.6L V8	4WD	109	101
HD Crew Cab SLE	6.6L V8	4WD	109	101
HD Crew Cab SLT	6.6L V8	RWD	109	101
HD Crew Cab SLT	6.6L V8	RWD	109	101
HD Crew Cab SLT	6.6L V8	4WD	109	101
HD Crew Cab SLT	6.6L V8	4WD	109	101
HD Extended Cab	6.6L V8	RWD	109	99
HD Extended Cab	6.6L V8	RWD	109	99
HD Extended Cab	6.6L V8	4WD	109	99
HD Extended Cab	6.6L V8	4WD	109	99
HD Extended Cab SLE	6.6L V8	RWD	109	99
HD Extended Cab SLE	6.6L V8	RWD	109	99
HD Extended Cab SLE	6.6L V8	4WD	109	99
HD Extended Cab SLE	6.6L V8	4WD	109	99
HD Regular Cab	6.6L V8	RWD	109
HD Regular Cab	6.6L V8	RWD	109
HD Regular Cab	6.6L V8	4WD	109
HD Regular Cab	6.6L V8	4WD	109
HD Regular Cab SLE	6.6L V8	RWD	109
HD Regular Cab SLE	6.6L V8	RWD	109
HD Regular Cab SLE	6.6L V8	4WD	109
HD Regular Cab SLE	6.6L V8	4WD	109

Trim	Eng.	Drive train	1st Row Headroom (cm)	2nd Row Headroom (cm)
HD 3500 Crew Cab Denali	6.0L V8	RWD	108.7	102.9
HD 3500 Crew Cab Denali	6.0L V8	4WD	108.7	102.9
HD 3500 Crew Cab SLE	6.0L V8	RWD	108.7	102.9
HD 3500 Crew Cab SLE	6.0L V8	4WD	108.7	102.9
HD 3500 Crew Cab SLT	6.0L V8	RWD	108.7	102.9
HD 3500 Crew Cab SLT	6.0L V8	4WD	108.7	102.9
HD 3500 Crew Cab Work	6.0L V8	RWD	108.7	102.9
HD 3500 Crew Cab Work	6.0L V8	4WD	108.7	102.9
HD 3500 Extended Cab SLE	6.0L V8	RWD	108.7	98.3
HD 3500 Extended Cab SLE	6.0L V8	4WD	108.7	98.3
HD 3500 Extended Cab SLT	6.0L V8	RWD	108.7	98.3
HD 3500 Extended Cab SLT	6.0L V8	4WD	108.7	98.3
HD 3500 Extended Cab Work	6.0L V8	RWD	108.7	98.3
HD 3500 Extended Cab Work	6.0L V8	4WD	108.7	98.3
HD 3500 Regular Cab SLE	6.0L V8	RWD	108.7
HD 3500 Regular Cab SLE	6.0L V8	4WD	107.7
HD 3500 Regular Cab Work	6.0L V8	RWD	108.7
HD 3500 Regular Cab Work	6.0L V8	4WD	107.7