727 lag and bump

witorque · Post by **witorque** » Mon Oct 11, 10 10:25 pm

My 72 340 Challenger has a minor transmission issue. When applying 2/3 or more throttle suddenly mostly at low speeds, there is what I would call a lag and bump in the transmission. It is not the upshift, but a feel of maybe a clutch in limbo, then engaging suddenly.
I backed off the downshift a bit, but I don't think this helped
This problem only occured after the transmision was rebuilt.
A mild shift kit was fitted
Any ideas what the problem is?

Anonymous · Post by **Anonymous** » Wed Oct 13, 10 8:54 pm

Hi Chris,

Could be band adjustment, but more likely the rear clutch pack, or the accumulator is sticking, are you using a standard spring under the brain or a 'blocker rod' or nowt?

Bacca.

witorque · Post by **witorque** » Fri Oct 22, 10 10:49 pm

It has only done just over 1000 miles since being profesionally rebuilt, so one would expect the bands to be adjusted correctly. I spoke to the guys that rebuilt it, they said they would have a look at it. The trouble is they are in East Sussex about 150 miles away, so that is a full day and over £100 in petrol...
Should I drop the pan and investigate myself? My knowldge of auto transmissions is vague. Would a sticking accumulator be obvious with the valve block dropped?
Closest I've got to rebuilding something like this are laycock A type overdrives, and I've done a few of them
I could take it to a local auto transmission specialist, but would the average specialist know a 727?

latil · Post by **latil** » Sat Oct 23, 10 8:19 am

East Sussex? hope that's not Alders,a few tales around about their work. Do you have anyone local that's familiar with Jensens or early Range Rovers? They use the same trans.

Cannonball · Post by **Cannonball** » Sat Oct 23, 10 9:10 pm

witorque wrote:My 72 340 Challenger has a minor transmission issue. When applying 2/3 or more throttle suddenly mostly at low speeds, there is what I would call a lag and bump in the transmission. It is not the upshift, but a feel of maybe a clutch in limbo, then engaging suddenly.
I backed off the downshift a bit, but I don't think this helped
This problem only occured after the transmision was rebuilt.
A mild shift kit was fitted
Any ideas what the problem is?

chris
when you say a lag and bump do you mean it loses drive ??? then thumps back in ??????????

witorque · Post by **witorque** » Sat Oct 23, 10 10:11 pm

Well almost, but only if you floor the throttle. It is not noticable using light throttle. There may also be a slight tendency to delay 2nd to 3rd upshift at full throttle
I didn't mention that after the unit was reconditioned, it stood on the garage floor for 2 years before being fitted. Is there anything prone to stick maybe due to a little internal condensation?

Cannonball · Post by **Cannonball** » Sat Oct 23, 10 10:18 pm

witorque wrote:Well almost, but only if you floor the throttle. It is not noticable using light throttle. There may also be a slight tendency to delay 2nd to 3rd upshift at full throttle
I didn't mention that after the unit was reconditioned, it stood on the garage floor for 2 years before being fitted. Is there anything prone to stick maybe due to a little internal condensation?

valves can stick but prob unlikly in this case, you need to go drive it again and log what you think its doing wrong then repost
see if i can understand it better

witorque · Post by **witorque** » Sat Oct 23, 10 10:25 pm

If I disconnected the downshift to see if the problem still occurs, would this help diognosis?

Anonymous · Post by **Anonymous** » Sun Oct 24, 10 5:35 pm

Hi Witalk,

If I visit me MuM in West Horrington anytime soon I will pop in and have a lookie at the trans for thee!
Just thought, are you running a kickdown linkage???

Best wishes Bacca.

witorque · Post by **witorque** » Mon Oct 25, 10 4:42 pm

Yes, sounds good to me we'll take it for a spin
Original rod kickdown is fitted
Could the bump be the convertor stalling / locking up?
Just let me know nearer the time
-Car will be at the NEC 11th - 14th November
Chris

witorque · Post by **witorque** » Thu Aug 11, 11 7:57 pm

Found out what caused this
The comany that rebuilt it left the inner spring out, that loads the pressure relief valve spool when they installed the mild Transgo shift kit....
The transmission clutches were dropping out due to lack of pressure at idle.
As a result the middle clutch plates were badly worn after just a few thousand miles....
Rear brake band had to be replaced also.
As the rebuilt transmission stood here for over 2 years before going back in the Challenger, I couldn''t really confront the comany in East Sussex who I took it to in the first place. I only took it there because I saw their Ad in American car magazines, claiming they specialised. Needless to say I would never use them again.
Local company I.C Automatics at High Littleton south of Bath did a good job of putting it right. Wish I'd used them in the first place. We live and learn.

Derek · Post by **Derek** » Thu Aug 11, 11 11:16 pm

witorque wrote: I couldn''t really confront the comany in East Sussex who I took it to in the first place. I only took it there because I saw their Ad in American car magazines,

Would that be Allders.

latil · Post by **latil** » Fri Aug 12, 11 7:18 am

latil wrote:East Sussex? hope that's not Alders,a few tales around about their work. Do you have anyone local that's familiar with Jensens or early Range Rovers? They use the same trans.

What I said.

witorque · Post by **witorque** » Fri Aug 12, 11 7:57 pm

I don't think it would be right to say, but that's a good guess

Cannonball · Post by **Cannonball** » Fri Aug 12, 11 9:05 pm

what i have found with a lot of the transmission shops is they just dont have the hardware to replace some of the hard parts that are a bit worn on our old time transmissions so faced with that they will just reseal them new friction and some dont even overhaul the valvebody just wash the surface crap off so its a bit off a cockup, i bought 50 odd full transmissions from the states so if i come accross a part that is not 100% it can be changed for a perfect item dont forget this transmission harks back to the early 60s the parts new are rare or big $$$$$$$$ FROM THE USA

BUT Bananarama! HAPPENS AND YOU CAN SOON GET SLAUGHTERED WHEN ONE GOES WRONG..........

Mopar Muscle Association UK

727 lag and bump

727 lag and bump

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