I just road tested my car today after installing everything from a hardtop 91 Formula 350(engine, TPI, 700R4, rear end, memcal etc.) but I haven't changed the instrument cluster its still the 305 120mph cluster.

On the road test its not shifting right which I believe is just adjusting the TV-detent-kickdown cable.

I notice that the speedo isn't working at all and no SES light. Every other gauge is working.

Would the VSS go bad without throwing a code?

 

i just did a swap myself, and had a speedo problem, i also swapped the buffer box from donor car, and that fixed it. hope that may help.

 

I didn't take the buffer box from the donor car but I didn't think the buffer would be any different from the same year car. 1 having a 305 TPI and the donor a 350 TPI.

I take it you left the original buffer and had the speedo problem and then changed it from the donor car and it fixed the speedo problem?

Where in Georgia are you?

 

im in pine mountain,FDR STATE PARK, calloway gardens.when i did the swap, my speedo and shifting, as well as the tach were goofin up,i checked the vss,looked good, and swapped the cluster, same thing, so i swapped the buffer, and everything started to work as it should.now, i did swap from a different year, so that may play into it. i went from 87 to 89. lucky for me, i had a complete car to pull from.

 

I did have the complete car and took everything I thought I would need for the swap for sending it to the crusher. Over the years I thought I read everything out there about this swap and I don't recall ever seeing the buffer mentioned especially in the 90-92 TPIs.

I don't believe its the VSS because it was working in the Formula before I pulled everything. The cluster and the buffer are the only things I didn't change. I'm leaning to the buffer but I'm going to check my parts manual and see if I find a difference.

The buffer caused a shifting problem in your car before you changed it?

 

My parts manual shows the same P/N for buffers 85-92 in all engine types. I have found these manuals to be wrong in the past though.

 

both of my buffers showed dif numbers on them.(looked the same)
when i swapped them out, my shift points dropped lower,

 

I need your help. I can't remember were the buffer is located. My friend on here is parting a 92 350 TPI TA out and its going to the crusher this saturday. He will pulled it for me but needs to know were it is and what it looks like. I remember it being stamped buffer and might be yellow but I can't remember if thats right and were its exactly located.

THx for your help.

 

Sounds like the buffer is the cause of all my issues including the shifting.

 

both of mine were yellow boxes, located up inside the pass side of the dash.i opened both, and slight diff in both panels, this could be the diff.???

 

Thats what I thought but wasn't sure.

Us Georgia boys need to stick together and I thank you for all your help.

 

Did some research on here and in my service manual. 90-92 only used an external buffer on the 305 TBI 746 ECM. The 3.1, 5.0, 5.7 TPIs all used the 730 ECM and the buffer is built into the ECM.

I'm back to square 1.

Looks like its down to:

1. VSS
2. Speedo (I have 5 spare clusters)
3. ECMs internal buffer (I have 3 ECM spares)

I'm no electrican but from what I'm seeing on the wiring diagrams is that if the VSS goes bad the speedo won't work.

BUT will it effect tranny shifting points?

 

Nope.
The transmission is the hydromatic model, it's operated internally from the valve body. The ECM has no control over the shifting, nor has the transmission any electronic speed input for its shift points. It's all done hydraulically.

Hope this helps.
Lou