I am thinking of changing my 70 GS 455 Muncie M-20 (factory) out for a Tremec 5 or 6 spd. Has anyone had any experience with this? If so is there a ton of mods. or is it pretty straight forward? I've already installed a posi 8.5 10 bolt ('71 skylark) which required shortening the driveline so I'm not scared of a little bit of modifying but I want stock appearence. Thank you in advance, Dave
You will have to get the Tremec for GM applications. There are more than one version as well, the TKO-3550, TKO-500 and TKO-600. The final two rated for their torque capacity. A-bodies need a large amount of cutting of the tunnel area to accomodate the taller Tremec. The input and output shafts are different than your M20. The input shaft fix is a new clutch disc, the output requires a different yoke (available from the Tremec vendors). A new driveshaft length will be required. The tremec has a mounting tab on the bottom that is used for F-bodies that some grind off to add clearance between the road and the transmission. A new shifter will be required as the Tremec is a toploader. But it really is a pretty straight forward swap. Buickgsman and staged67gspwr has done this swap. What is your rearend ratio? As the Tremec has a lot different gear ratios than the Muncie.
Greg pretty much summed it up. Here is a pic, but this wasn't the final chop of the floor. I stopped taking pictures because i was sick to my stomach. Kessler says you don't have to cut much, but they are full of cr@p. I had to go all the way up the front of the floor and all the way back past the trans and clear across the floor until it flattened out.. MAJOR cutting, but its a sweet transmission. The console fit back in and if you don't have a 4 speed GS next to it to compare it to, it looks totally stock, except for the 5 speed shifter ball. Would I do it again? Probably not, but I don't drive the car that much.
I didnt cut as much as buickgsman but i had to cut alot as well,i also used the Mcleod slik stix offset shifter http://www.mcleodind.com/ProdGuide/PG_PDFs/Page 15.pdf to fit my console,i dont know if i would do it again either but i tell you its a blast to drive on the highway with the OD. Thanks
My shifter and console on my hardtop(5-speed)seem to be in the same position as my conv`t`s(4-speed) here are a pic of my hardtop and conv`t. Thanks
Thanx for the info. and pics. Was buickgsman a conversion from an auto matic to manual? It's my understanding that manual tunnels are different and don't require as much cutting (according to the people trying to sell Tremec). Is this misinformation(bull)? Again this is the best response I've received to date thank you! Dave
Dave thats BS they had told me the same but i had to cut the tunnel anyway,they just say that to sell you the trans. Thanks
I'm in the same boat as Dave, i have a 72 gs 4 speed project car, with no tranny, I want to build a occasional driver and but was thinking of a 5 or 6 speed. A friend of mine has a 66 chevelle that had a 4 spd muncie and he installed a 6 speed & loves it but he too was told it'll bolt right in, but had to do much cutting and modifiying, he admitted he should have gone with an overdrive unit on his muncie. Based on the photos provided by buickgsman, of the cutting required I don't think I want to butcher the original floor on mine as it is in fairly good shape. Has anyone used an overdrive setup that bolts to the muncie? My buddie with the chevelle will give me his muncie, what needs to be done for the overdrive install? Shorten driveshaft obviously.. any cutting, welding or additional bracket-tree? thanks & sorry to butt in or your thread Dave
No problem butting in. I don't want to butcher the car and am also interested in alternatives. I didn't know overdrive units were still available. where would I find information about them? Dave
Hey Dave, I'm sure someone will jump in here and soon reply that knows of the overdrive units, I was recently at SEMA and think I saw a booth that sold overdrives that attach to the rear of the muncie? I was with my buddie and by then had convinced me the 5 or 6 speed was the way to go so I didn't get any brochures or info, damn it...I was overwhelmed at SEMA and didn't allow enough time to check out all the resources for restoring the gs. I'll try a google search and see what I come up until then, we'll wait for someone thats done overdrive unit to advise us...ttyl, Gord
Dave i think these guys do the overdrive units? Can anyone offer us some advice? http://www.gearvendors.com/cg2wdt.html http://www.autogear.net/literature2.htm#
My car was a factory t-350 car, but I had swapped in a muncie prior to the 5 speed. The tunnels are all the same, the only difference is the shifter hump that you would weld to the floor. I don't know why I had to cut so much of the floor, but it was a lot. It kinda freaked me out... but at that point you already have the trans, its in the car and what the he!! are you supposed to do.. say forget it? Keep cutting! I think if i do an overdrive again, I would slap a gear vendors o/d on the back of a turbo 400. Not a stick, but thats supposed to be a bulletproof combo, and i think all that is required is denting the floor a bit. But again, the tremec is sweet!
I used a Richmond 6 speed. Very little banging, cutting or fabing. Need to move the crossmember back which should only require two holes & need a new driveline with TH400 yoke. Seriously, not too hard. A lot less work than the Tre-mec by the looks of the pics.
I have a richmond 5 speed and it's tight, but you do not have to cut up the floor. You do have to move and modify the crossmember. These trannies are sweet, I would highly recomend them. My turbo motor makes 637 Ftlbs of torque at the rear wheels and the 5 speed just keeps takeing it. Thanks Brent
Whos got the best pricing on the richmond 6 speed setup or do you buy direct from Richmond. thanks gord
Go Richmond I am using an older Doug Nash 5 speed, which is identical to the Richmond trans. The car was originally an automatic. I had no problems fitting the 5 speed in the car. If I ever need another trans, or get the $$ for an overdrive, It'll definately be for a Richmond. They are externally just like the original style Muncies. I prefer only one overdrive as compared to two anyway!
Hey Andrew, thanks for the advice, its going to be a richmond for me, I was going to stay with the muncie but changed my mind now. Nice wheels/tires on your 72, whats the tire and rim sizes and offsets? Did you do suspension & brake mods as well? I've got a 72 and I'll want to drive it and have it handle on the hiways at speed and cruising around town. If you want to shoot me a pm: gord@tramin.ca
