Trans Tunnel - The 1947 - Present Chevrolet & GMC Truck Message Board Network

68crum · 04-12-2006, 10:25 AM

I have a 68' with a I/6 and a powerglide, I'm getting ready to put in a 454 and a strong built th/350. The cab has a small trans tunnel. Am I going to have a trouble? Do I need to install a large tunnel? Would like to know before I acually try to put it in.

Longhorn Man · 04-14-2006, 02:24 AM

Stock would have comew with a high hump and my train of thought is that they did that for a reason.
With that being said there are quite a few ppl here that'll tell you it'll fit no problem as long as you have good cab mounts.

71/454 · 04-14-2006, 02:32 AM

I have a 454/t350 combo in mine and it fit ok. I swapped from a 350 and used 73 and later mounts. I may be wrong but I believe that you could not geta big block in these year of truck without a turbo400. I dont think gm ever made a big block t350 combo. I say this because I went looking for a kickdown bracket for my bigblock and found I had to make one or use an aftermarket because according to the old guys in the car club gm never made that combo and a t400 has an electric kickdown. Hope this helps and am interested to see what everyone else thinks

68crum · 04-14-2006, 08:22 AM

Just made a SWB out of it, put in new cabmounts, rockers, and cab corners. Hopefully it will fit no problem.

shifty · 04-14-2006, 09:20 AM

i don't know how the 454+350 measures up to an LS1+T56, but i had to swap to a high hump. it's actually not that hard of a process, i just can't figure out where to get the proper nut strips that are supposed to be on the underside of the cab to mount the hump to the floor.

with that said, if i would have had a 4L60E, i think i could have gotten by with no problems.

**breeh** · 04-14-2006, 01:41 PM

I think that the trans hump has more to do with the trans used than the motor used. I just pulled an untouched truck apart that had a TH400 in it. I assumed that it would have a high hump but it did not. I don't think that you will have any problems.

Longhorn Man · 04-14-2006, 01:51 PM

Has nothing to do with the trans when it comes to automatics.
The only way you could get a big block truck from GM with a low hump, would be with the 3 speed manual shift.
Small blocks with TH400's got the small hump.

All big block autos
All 4X4 trucks
All 4 speed trucks
and GMC V-6/auto (1/2 ton only)
came with high hump.

**breeh** · 04-14-2006, 03:07 PM

I remember at one time that someone posted that all TH400's got the high hump. It just goes to show that you have to take all of the info here with a grain of salt. I have seen many of these "rules" broken by the General too.

Longhorn Man · 04-14-2006, 04:16 PM

Yeah, the general did in fact break the rules back in the day... however, no, TH400 trucks did not automaticly get a high hump. By the rules, TH400 would have only gotten a high hump if it was a 4X4 (did they come with TH400's???) and if it was a big block, or a GMC V-6 motor.

04-12-2006, 10:25 AM	#1
68crum Proud owner of a P.O.S. Join Date: Oct 2005 Location: little rock, Ar Posts: 72	Trans Tunnel I have a 68' with a I/6 and a powerglide, I'm getting ready to put in a 454 and a strong built th/350. The cab has a small trans tunnel. Am I going to have a trouble? Do I need to install a large tunnel? Would like to know before I acually try to put it in.

04-14-2006, 02:24 AM	#2
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	Re: Trans Tunnel Stock would have comew with a high hump and my train of thought is that they did that for a reason. With that being said there are quite a few ppl here that'll tell you it'll fit no problem as long as you have good cab mounts.

04-14-2006, 02:32 AM	#3
71/454 Turbo Guy Join Date: Jan 2005 Location: Calgary Alberta Posts: 353	Re: Trans Tunnel I have a 454/t350 combo in mine and it fit ok. I swapped from a 350 and used 73 and later mounts. I may be wrong but I believe that you could not geta big block in these year of truck without a turbo400. I dont think gm ever made a big block t350 combo. I say this because I went looking for a kickdown bracket for my bigblock and found I had to make one or use an aftermarket because according to the old guys in the car club gm never made that combo and a t400 has an electric kickdown. Hope this helps and am interested to see what everyone else thinks

04-14-2006, 08:22 AM	#4
68crum Proud owner of a P.O.S. Join Date: Oct 2005 Location: little rock, Ar Posts: 72	Re: Trans Tunnel Just made a SWB out of it, put in new cabmounts, rockers, and cab corners. Hopefully it will fit no problem.

04-14-2006, 09:20 AM	#5
shifty Questionable Join Date: Mar 2005 Location: Atlanta Posts: 13,376	Re: Trans Tunnel i don't know how the 454+350 measures up to an LS1+T56, but i had to swap to a high hump. it's actually not that hard of a process, i just can't figure out where to get the proper nut strips that are supposed to be on the underside of the cab to mount the hump to the floor. with that said, if i would have had a 4L60E, i think i could have gotten by with no problems. __________________ If I've got anything up for grabs, it'll be here: 7-hole gauge cluster for a 67-72 p/u FREE (link) I can't check the forum daily. If I don't reply to you within 24 hours, drop me a PM! I'm (hopefully) still alive and will reply faster to a PM.

04-14-2006, 01:41 PM	#6
breeh Recovering 67-72 Addict Join Date: Oct 2000 Location: North Bend, WA Posts: 1,788	Re: Trans Tunnel I think that the trans hump has more to do with the trans used than the motor used. I just pulled an untouched truck apart that had a TH400 in it. I assumed that it would have a high hump but it did not. I don't think that you will have any problems. __________________ 68 Short Fleet 4x4; 427; BTO Level 3 700R4; NP205; Dana 60 front and rear; 4" lift with 35's; Disc brakes; AGR variable ratio steering; factory bucket seats; factory tach and tilt. "Friends call me cruzer cuz I like fast cars and fast women"

04-14-2006, 01:51 PM	#7
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	Re: Trans Tunnel Has nothing to do with the trans when it comes to automatics. The only way you could get a big block truck from GM with a low hump, would be with the 3 speed manual shift. Small blocks with TH400's got the small hump. All big block autos All 4X4 trucks All 4 speed trucks and GMC V-6/auto (1/2 ton only) came with high hump.

04-14-2006, 03:07 PM	#8
breeh Recovering 67-72 Addict Join Date: Oct 2000 Location: North Bend, WA Posts: 1,788	Re: Trans Tunnel I remember at one time that someone posted that all TH400's got the high hump. It just goes to show that you have to take all of the info here with a grain of salt. I have seen many of these "rules" broken by the General too. __________________ 68 Short Fleet 4x4; 427; BTO Level 3 700R4; NP205; Dana 60 front and rear; 4" lift with 35's; Disc brakes; AGR variable ratio steering; factory bucket seats; factory tach and tilt. "Friends call me cruzer cuz I like fast cars and fast women"

04-14-2006, 04:16 PM	#9
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	Re: Trans Tunnel Yeah, the general did in fact break the rules back in the day... however, no, TH400 trucks did not automaticly get a high hump. By the rules, TH400 would have only gotten a high hump if it was a 4X4 (did they come with TH400's???) and if it was a big block, or a GMC V-6 motor.



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