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View Full Version : Clutch/Torque Converter: Thumping taking off in 1st gear: 2R6 T86/OD



jackb
06-15-2018, 02:46 PM
This just started happening to my truck. Whenever I take off from a stop, in 1st gear, I hear a thumping(?) type sound from under the hood (?). This does not repeat itself in reverse. I believe there is no sound in 2nd or 3rd and no real discernible loss of power or performance. I can eliminate the sound if I depress the clutch. The clutch works fine without any other squeals or vibration. I thought it was the hood vibrating, but opened it slightly and the sound remains. I did replace the water pump recently, and the belt may need tightening (tho I like to keep them on the loose side for pump life). The noise doesn't matter if the wheels are straight or in either direction and there is no change in tracking down the road. Engine temperature has no affect on this.

swvalcon
06-16-2018, 07:43 AM
I would take a look at the trans mount.

rockne10
06-16-2018, 03:01 PM
I would check ALL motor/trans mounts.

StudeRich
06-16-2018, 03:33 PM
Is there a fan Shroud for the Fan Blades to hit?

Does your Air Cleaner have a "Snorkel" on it, that could hit the Firewall?

jackb
06-17-2018, 07:52 AM
I thought of the mounts: I replaced the rubber insulators about a year ago..... NOS about a year ago.... Perhaps the mounts themselves to the frame....truck is in the paint booth now...

jackb
06-28-2018, 08:17 AM
So..... after paint, and still to get inside for refreshing there, I talked with an old Stude truck mechanic who may be on to something: damaged 1st gear. It could make sense to me because after replacing all 4 engine mounted rubber cushions, I needed to adjust the gear rods (T86A w/OD). On 2 occasions, after adjustment (alone), when I thought it was in "neutral", there was a distinct "BANG" as I released the clutch. The 2nd time @ the filling station (!), was the worse of the 2. The noise didn't start immediately, maybe several months later. I have it up on jack stands now and will run it in 1st gear..... Should I hear some grumbling ??? Or likely under pulling on the ground . Comments ? I assume T96 parts are readily available..? I have access to replacements and a T85.....Commander 6 ??

Chipmaker
06-28-2018, 09:16 PM
It sounds like a bad or broke tooth on the low part of the cluster gear.

RadioRoy
06-28-2018, 11:53 PM
I would think you should hear some grumbling in first gear. The question is how much? Probably any thumping would be bad.
Whenever I listen to my generators with a mechanics stethoscope, it's amazing how noisy they are - and are still good.

T-86 parts are available, since Ford and all/most of the independents used them.

New T-86 parts are not cheap, however. But... there should be plenty of used transmissions around and some of them would yield good parts.

I don't think many T-85 parts would interchange with the exception of some overdrive parts.

Since it's a truck, you might have a T-90, which looks like a T-86 on the outside, but has different first gears than the T-86. The T-90 gears are straight cut and stronger, but inherently noisier than the beveled gears in the car T-86.

But not to get ahead of ourselves until the actual culprit is identified.

Kurt
06-29-2018, 05:55 AM
Check to see if the adjustment on the shift rods is ok. If low is not fully engaging you will get a thumping sound. If it has lost adjustment you likely have worn mounts as well

jackb
06-29-2018, 07:46 AM
I should have clarified: I have access to a T85 which I thought was a H.D. 3 speed for later Big 6 & V8 trucks ?.....

StudeRich
06-29-2018, 04:36 PM
I should have clarified: I have access to a T85 which I thought was a H.D. 3 speed for later Big 6 & V8 trucks ?.....

These Borg Warner Manual Transmissions can be a bit confusing because the CASES Cast with "T-86" or "T-85" can be as marked OR; a T-86 CAN have Truck straight cut, Lower Ratio Gears and actually BE a T-90!

The same with the H.D. T-85 Car Trans. with the removable Left Side Cover instead of Top, it CAN be a T-89 For Trucks.

The Commander 6's used a T-90, not T-85 or T-89.
"I believe" the T-90's (Truck & Taxi) came with "170" c.i.d. size Input Shafts or "245" Shafts.

Skip Lackie
06-30-2018, 08:36 AM
Since it's a truck, you don't have to pull the trans to look at the gears. Remove the inside hump cover and then take the top off the trans.