Jim, I know you installed a tremec in your car,did you have any tunnel clearance issues? i have been through the "tunnel clearance" forums on the site...and I've got new bushings,got the right saddle mounts on the motor and I have very minimal floor sag...and I got zero and I mean Zero clearance between the trans and the tunnel,did you have any problems,and please everyone chime in here cause I know this is a common swap on 1st gens so give me your experiences

you out there Jim?

ya ya, I'm out here... jeez, you post at 11:30 at night then7:30 Saturday morning? I know I live here, but heck even I gotta sleep once ina while! :)

Tunnel clearance was VERY tight, but not quite touching. I used a CC5S tubular crossmember and the trans mount came from fortes. The "second time" it went in and out, had to lower the back of the motor to do it.

Had to put the crossmember in place first (bolts loose) then jack the trans up against the tunnel and beat the mount in place. I stuck a couple of peices of paper between the top of the trans and the tunnel. Once everything was bolted up, I was able to pull the paper out without tearing it, but not without some resistance. It is VERY close to the top of the tunnel, mostly the vent cap and the rearmost bolts that hold the top plate on the trans. I did not "adjust" the tunnel, but would have ig the paper tore. I've also heard of people having to drill a clearance hole where that vent cap is.

If you are using a poly tranny mount take the metal plate out. that is what I did and my tranny barely has a paper's worth of clearance.

Sorry Jim I thought you were a west coaster so the 11:30 thing was after I got done messing with my car last night...the 7:30 thing,well I got a three year old and need I say more...Anyway I used all the regular mounting stuff that came with the trans.I to had to put everything in loose and use some persuading on the crossmember and mount,think I'm gonna try the floor pan adjustment as suggested in the forum.I gotta ask tho' with that little amount of clearance does the trans. bang against the floor pan when you get on it...I gotta believe that there is 1/4 in. movement,at least, in torque when you get after it. Also the mount and crossmember you said you installed...I think the crossmember is the classic chevy one but what about that mount...could that be a little thinner than mine?

I'm unfortunately not sure exactly where my mount came from. I bought the trans used, and the mount came with it. Perhaps Don could enlighten us on this? But I think he just threw the new mount that came with his new trans into the box he sent me.

I do not get any rubbing or banging that I can hear/feel over the motor and flows at WOT. It doesn't bang just driving, either. I use rubber motor mounts, too.

Jim, I thought mods had to wake up in the middle of the night to check the forums? :p
and why do you need sleep anyway!!!
ya ya, I'm out here... jeez, you post at 11:30 at night then7:30 Saturday morning? I know I live here, but heck even I gotta sleep once ina while! :)

I'm unfortunately not sure exactly where my mount came from. I bought the trans used, and the mount came with it. Perhaps Don could enlighten us on this? But I think he just threw the new mount that came with his new trans into the box he sent me.

I do not get any rubbing or banging that I can hear/feel over the motor and flows at WOT. It doesn't bang just driving, either. I use rubber motor mounts, too.


Been up since 4 am,, its an oilfield thing that grows on you thru the years. Jim got my Tk0500 and I believe he got the stock style hallow mount. I thought I would stiffen up the back some going to the 600 and install a poly mount, wrong, I felt too much road feel thru the trans and put a stock hallow mount back.
As for clearance, Jim is correct, its tight but what you feel most is the little vent on top of the trans that hit first. I just wonder if the road feel I was getting in the floor was actually the vent hitting the floor with the poly mounts as its solid. I did even remove the mount plate. So it must have been tight. So I am back to stock mount.
Bent a clothes hanger rod and checked for clearance and it passed , tight so thats all clearance I had between floor and vent cap..

Been up since 4 am,, its an oilfield thing that grows on you thru the years. Jim got my Tk0500 and I believe he got the stock style hallow mount. I thought I would stiffen up the back some going to the 600 and install a poly mount, wrong, I felt too much road feel thru the trans and put a stock hallow mount back.
As for clearance, Jim is correct, its tight but what you feel most is the little vent on top of the trans that hit first. I just wonder if the road feel I was getting in the floor was actually the vent hitting the floor with the poly mounts as its solid. I did even remove the mount plate. So it must have been tight. So I am back to stock mount.
Bent a clothes hanger rod and checked for clearance and it passed , tight so thats all clearance I had between floor and vent cap..

Are you saying you used a stock G.M. rubber type mount...I havent looked all that close at it,but does a stock mount work? Is there any difference in height?

I used a stock rubber mount for a TH350/Glide, and I have 1/4" or more at the tightest spot. I have the CC5S crossmember and stock height solid GW subframe bushings.

If you go to one of the stores with computer lookup, make sure you get the TH350/PG mount, and not the TH400 mount, which is thicker/taller. Depending on the lookup system, whether it tells trans model or not, or RPO (M35/M38 for PG/TH350, M40 for 400), you're best bet is have them pull both and make sure you take the short one.

Are you saying you used a stock G.M. rubber type mount...I havent looked all that close at it,but does a stock mount work? Is there any difference in height?

I could not see any differance in height but the center is hollow, molded front and back , thus leaving some crush range, you would think that the hollow area would allow to bounce more being the Tremac is some 25# or so heavier but then its the same mount as a th350 so, take it from there.
I used the four bolt type, from parts store, Two on the top and two on the lower. I used the batwing type trans crossmember from Fortes thru Mike Pell.
Thinner but 1/2'' bent plate with a few gussets. Moulded to fit around my exhaust. Fit like a glove.

When I did this swap, the clearance was also very tight. That is with full thickness aluminum body mounts. I added a few large washers between the frame mounts and the floor to give it and extra 1/8 to 1/4 inch clearance. As a side benefit this also increased air cleaner clearance with the hood.

You talking about putting washers between the subframe and floor pan at the 4 points where you bolt the body to the frame?

As everyone else has already mentioned...my clearence was also very very tight. IF you could slide a sheet of paper thru in some spots youd be doing good..at least on mine. I have stock rubber bushing. I have not had any problems with it being that tight however...and dont expect you will.

When I did this swap, the clearance was also very tight. That is with full thickness aluminum body mounts. I added a few large washers between the frame mounts and the floor to give it and extra 1/8 to 1/4 inch clearance. As a side benefit this also increased air cleaner clearance with the hood.


Brings another question,, are his body mounts gone?