Inliners International Forums General Discussion Drive Train T5 rear support

Is a rear support (tailshaft housing) needed if the I have bellhousing motor mounts?

I have had the T5 in our truck for a while but am a little scared to push it REAL hard to see what the truck will do because of the lack of the rear support.

All the T-5's I've seen have a rear mount built in to them. I take that as a sign that it needs to be mounted in the rear. I used a crossmember to mount mine. It can't hurt anything to use it.

All the T5's were behind "modern" engines/bellhousings with just the engine block mounts, thus they needed a tailshaft support.
Are you talking about the old cast iron Chevy bellhousing??
I've heard both yes and no to this. With the dual bellhousing mounts, it's probably not necessary to support the tailshaft. Millions of them were, and still are, in service with a 3 speed hanging out behind with no support.
However, as an "overbuilder" I was planning on using a tailshaft support also (TKO-500). I would think it should provide "gentle support" but not be too rigid -definately rubber, not polyurethane in my opinion.

The 'not too rigid' is my concern. Every driveline develops a twist (torque) during it's highest acceleration. I was concerend that securing the tailshaft might keep this from happenning and create a loud snap, a blood red mess on the road, a wrecker bill and several profanities.

I was considering using the S10 mount that has a single bolt to hold the mount to the crossmember and then I was going fabricate a 3 piece crossmemeber that would have 2 isolators on each side attaching the flanges to the piece the motor mount is attached to. Do you think that might be too loose?
I was also considering making some supports that attach to the bellhousing mount bolts. I've seen something similar at the junkyard on 4 wheel drive S10's.


Basically, I'm trying to make my T5 tailshaft housing last forever. I had a tough time finding a good used T5 with a mechanical speedo for less than $150 that didn't need $250 worth of parts.

My son can't wait to take this truck to the track to see what it will do, but I'm not willing to push it that hard until I figure out the transmission rear mount issue.

I would lose the bell housing mounts and make a rear cross member.
If you use the bell mounts with a rear mount, problems will happen. This is chassis flex and the engine/ trans combo does not flex. Then something cracks. Tom

That makes more sense than using 5 points to mount engine and trans. I never thought of doing that.

Is there anything that needs to be done to the front mounts to handle the additional stress/load?

The front mounts are plenty strong. Only thing I would do is get new motor mounts. The newer desiged ones are interlocking to hold the engine if rubber fails. I use poly ones myself. Tom

Tom: Do you have a source for the poly ones you use? JimRJ

Jim,
I use a motor mount like these. If understood properly, your truck should also use a mount like these. It is a 2 piece with the poly mounts. Where as yours should be one piece now. Tom
http://cgi.ebay.com/ebaymotors/Energy-Su...sQ5fAccessories
I hate buying anything from Summit. They are like Walmart and will try their best to close up any competition and do not have the best prices.
I buy stuff like this from Performance Suspension Components in Arizona. Easy to look up. Tom

I was unable to find this 'positive' style mount a '67 C20. I contacted Performance Suspension, Jegs and Summit - all claimed htey don't have one. I couldn't find one in Energy Suspension's catalog either.

But I'm pretty sure I can fabricate a bracket that will attach to the motor mount and frame bracket for motor mount.

Do you have a pic of what your mount looks like?

Here's what I have

http://www.brotherstrucks.com/prodinfo.asp?number=SBMM072



On another note - have you ever seen the factory cable that Buick used to attach the driver side upper control arm to the exhaust manifold? The purpose was hold the engine down when the motor mount(s) seperated.

JimW and Tom,

The cable was a GM factory recall in the early 70's- they put one on my 68 Camaro with 327. I actually had a mount fail and I experienced the problem about '74. The rubber of the mount would seperate, the engine would lift the left side under hard acceleration, and bind the throttle linkage at Wide Open Throttle!! (and Toyota still is fighting this problem with a fly-by-wire throttle!!)

As Tom said, the Energy Suspension engine mounts interlock so that can't happen- but isn't that a different style mount from the one Jim shows. Jim, that mount you show is what is in my 63 with a 230. It is sandwiched between the perch and the engine mount with a bolt, so it can't come apart unless the bolt fails IIRC. Is that right???

As to using the 4 factory mounts versus a 3 legged approach, why did GM do it that way? a holdover from the days of heavier engines? which method would the T5 case/tailshaft fair best with?
I would think the 4 point mount would support the weight of the 292 better. If you eliminate the bellhousing mounts, and just use a tailshaft mount, ??? I don't know; maybe we should get one of the engineering guys to weigh in on this. I will email Tremec and ask them for an opinion.
-Tad

In the latter part of '64 it was factory installed on Buick 401 & 425 nailheads due to the wide open throttle problem you describe. Basically, they expected the driver side mount to seperate due to torque.

Engineer at Tremec - sounds great - let me know what you find.

You right - it has the bolt that passes through it, but I don't believe the bolt engages the opposite plate, but tonite, i'm going to find out. I'll attach a pic or two if I'm not sure.

http://img204.imageshack.us/g/1001063m.jpg/

These are pics of my motor mount.

It is not a 'positive' mount, but I'm positive I can make it a positive mount by doing one of two things:

1st - I could install a longer bolt through the center bolt (7/16 course) with 1.5" - 2" of threads and then install a locknut and washer through the threaded hole in the mount or

2nd - ream the threaded 7/16 hole in the mount and use a 2" bolt and locknut through the 7/16 hole.

Any suggestions?

Tom,
You were correct about the rear mount(s). I contacted my local (most local) T5 rebuilder and he advised to use the rear trans mount and lose the bellhousing mounts. He said that, if I used the bellousing mounts and tailshaft mount, at best I would break the ears off from the trans, need a case, and still be able to drive it home. Repeat - at best. Worst would be needing a wrecker and another transmission.

I have a T5 hanging off an old chevy truck bellhousing with no tail shaft mount. I have two side engine mounts up front and bellhousing mounts in the rear. I have had no problems in 15 years of operation in my 40 Chevy. The engine is a 302 GMC which has about 190 hp and I use an 11 inch clutch.

Have a T5 hanging behind a 235 in my '60 C10. O.E. mounts, 1 at frt of engine, 2 at sides of bellhousing. Ran a muncie M20 for 18 years before this trans. No rear mount, no problem. The general built these rigs with 3, 4 and even 5 speeds hanging off the back and if you've every pulled a Spicer, New Process of Clark transmission with the park brake you know how heavy they are.

Have you received a response from Tremec engineering?

p.s. I have a 250

Got a response from:
Brian Marazoni
Hurst Driveline Conversions
http://www.hurst-drivelines.com

They said use a tailshaft support, and eliminate the bellhousing mounts, just as you and Tom thought.

Hope this helps,
Tad

Heater63,
Thanks for your effort. It is greatly appreciated!
I'm convinced, I ordered an Energy Suspension rear mount.

g.m. dude and Radar

If I were mostly stock with my 250 (sub 200 ft/lbs of torque), then I would be fine with not using the tailshaft mount. I've read on multiple locations though that my T5 is rated for 265 ft/lbs. I believe that I'm near 250 ft/lbs give or take some. My engine is very similar to one of the T Lowe dyno runs and his engine, with the similar setup, made 258 ft/lbs on the test. (T Lowe's dyno setup had the same head - lump 1.84I/1.60E, the carb, intake & exh - 390 Holley, Offy 4 barrel, Langdon cast iron, cam lift and duration almost exactly the same, but he had .5 more compression. THANKS TOM LOWE)
Based on the dyno run and T5 info, I was concerned. Thanks for your input. All advise and experience is always appreciated.

I don't understand the hesitation to use 5pt mounting. I ran a 56 with front and rear motor plates with a rear crossmember for years with no damage. Before I put in the rear crossmember I was cracking bellhousings.

This is chassis flex and the engine/ trans combo does not flex. Then something cracks.
X2, there is always some "racking" motion (like warping a playing card between your fingers) from the chassis - if not from engine torque, then from spring wrap on braking, or simply big one-wheel bumps. If the transmission is tied down too tightly, something breaks.
Poly mounts are safer and last longer, but transmit more vibration (whether it's enough to annoy you is a matter of personal taste). The driver's-side rubber mount can be kept alive by simply limiting the engine's rotational motion with a simply short length of wire cable (yes, you can use a hemi-jointed billet torque arm, if you're Donald Trump - but it's not better). One end is looped to a thimble and clamp and goes to a large bolt or bracket on the left side, the other to the chassis, with enough slack that normal engine vibration doesn't tension it. It has no effect at all (no noise, no vibration) unless the engine torques over completely to the point where the rubber mount is going to tear, then stops the motion. About $3.00 covers all the parts, infinitely adjustable, I've had one on my V8 street rod for 12 years and adjusted it once (you can even adjust it with the engine running).

I Fab'd up this rear mount for my '40 coupe. It runs a T5 from an 1983 IROC coupled to a built 292. works great after 10 years and over 17,000 miles!

my 62 3/4 ton is getting a T5 transplant now. the mechanic used a simple piece of angle iron and bolted it to the crossmember and then to the trans mount. it's solid and simple. i wouldn't run a T5 without a support. that aluminum case is not strong enough IMHO. i'll up a pic of this mount later.